Earth-printshttp://www.earth-prints.orgThe DSpace digital repository system captures, stores, indexes, preserves, and distributes digital research material.Sat, 25 Jan 2020 09:46:40 GMT2020-01-25T09:46:40Z50691- Results from shallow geophysical investigations in the northwestern sector of the island of Maltahttp://hdl.handle.net/2122/10961Title: Results from shallow geophysical investigations in the northwestern sector of the island of Malta
Authors: Pischiutta, Marta; Villani, Fabio; D’Amico, S.; Vassallo, Maurizio; Cara, Fabrizio; Di Naccio, Deborah; Farrugia, D.; Di Giulio, Giuseppe; Amoroso, Sara; Cantore, Luciana; Mercuri, Alessia; Famiani, Daniela; Galea, P.; Akinci, Aybige; Rovelli, Antonio
Abstract: We performed geophysical investigations in the northwestern sector of the island of Malta to reconstruct velocity-depth models and provide shear-wave velocity profiles. We have chosen two sites, one located in Rabat (Malta) and another in the Golden Bay area. We used both active (seismic and electrical 2D-tomography, Multichanel Analysis of Surface Waves – MASW) and passive (2D arrays and single-station measurements using ambient noise) geophysical methods. Consistently with previous studies performed in this part of Malta, we have found that both sites are characterised by site resonance in the frequency range 1-2 Hz as an effect of the local lithostratigraphic succession that shows an impedance contrast at about 60-90 m depth. This resonance effect can have important implications on both seismic hazard as well as seismic risk evaluation of the region since the amplified frequency range coincides with the resonance frequencies typical of 5–10 storey buildings which are very diffuse in the Maltese Islands, especially after intense recent urbanization.
Sun, 01 Jan 2017 00:00:00 GMThttp://hdl.handle.net/2122/109612017-01-01T00:00:00Z
- Treatment of ground-motion predictive relationships for the reference seismic hazard map of Italyhttp://hdl.handle.net/2122/3748Title: Treatment of ground-motion predictive relationships for the reference seismic hazard map of Italy
Authors: Montaldo, V.; Faccioli, E.; Zonno, G.; Akinci, A.; Malagnini, L.
Abstract: In the framework of the 2004 reference seismic hazard map of Italy the amplitude of the strong-motion (expressed in
terms of Peak Horizontal Acceleration with 10% probability of non-exceedence in 50 years, referred to average hard
ground conditions) was computed using different predictive relationships. Equations derived in Italy and in Europe
from strong-motion data, as well as a set of weak and strong-motion based empirical predictive relationships
were employed in a logic tree procedure, in order to capture the epistemic uncertainty affecting ground-motion
attenuation. This article describes the adjustments and conversions required to eliminate the incompatibilities
amongst the relations. Particularly significant are distance conversions and style-of-faulting adjustments, as well as
the problems related to the use of regional relations, such as the selection of a reference depth, the quantification
of random variability and the strong-motion prediction. Moreover, a regional attenuation relationship specific for
volcanic areas was also employed, allowing a more realistic evaluation of seismic hazard, as confirmed by the
attenuation of macroseismic intensities.
Sat, 01 Jan 2005 00:00:00 GMThttp://hdl.handle.net/2122/37482005-01-01T00:00:00Z
- Ground-Motion Scaling in the Kachchh Basin, India, Deduced fromhttp://hdl.handle.net/2122/3762Title: Ground-Motion Scaling in the Kachchh Basin, India, Deduced from
Authors: Malagnini, L.; Bodin, P.; Akinci, A.
Abstract: We studied the excitation, propagation, and site effects in the Kachchh
basin of India by using ground-motion recordings from a temporary seismograph
network deployed to study aftershocks of the Mw 7.6 Bhuj earthquake of 26 January
2001. The Kachchh basin has been proposed as a useful analog region for studying
hazard in other earthquake-prone but slowly deforming regions, such as the central
United States. The earthquakes we studied ranged in size from about M 2 to M 5.2,
and travel paths ranged from a few kilometers to about a hundred kilometers. There
was a broad range of focal depths among the aftershocks, so the data were divided
into two overlapping subsets to test the sensitivity of the derived propagation and
source parameters to focal depth. Parameters we constrained include the source excitation
terms (related to stress drop), a frequency-dependent attenuation operator, a
geometric spreading function, and an operator to account for site effects. Our results
indicate that seismic-wave attenuation in Kachchh crust is very low, similar to other
continental intraplate areas such as central and eastern North America. We also estimated
seismic moments and stress drops for the earthquakes by fitting singlecorner-
frequency source-model spectra to the observed spectra, corrected for propagation
by using our derived parameters. Stress drops were found to scale with
seismic moment and to be rather high overall. By using a stochastic point-source
model to estimate mainshock ground motions, we found that the distance decay of
expected peak ground motions, assuming a stress drop of 15–20 MPa, compare well
with the scant observations for the Bhuj earthquake. Ground-motion predictions for
Kachchh, based on Bhuj aftershock data, support the idea that the region may have
similar hazard to proposed analog areas in North America.
Thu, 01 Jan 2004 00:00:00 GMThttp://hdl.handle.net/2122/37622004-01-01T00:00:00Z
- Implications of earthquake recurrence models to the seismic hazard estimates in the marmara region, Turkeyhttp://hdl.handle.net/2122/10963Title: Implications of earthquake recurrence models to the seismic hazard estimates in the marmara region, Turkey
Authors: Akinci, Aybige; Murru, Maura; Console, Rodolfo; Falcone, Giuseppe; Pucci, Stefano
Abstract: In this study, we show the effect of time-independent and time-dependent occurrence models on the seismic hazard estimations. The time-dependency is introduced by 1) the Brownian Passage Time (BPT) probability model that is based on a simple physical model of the earthquake cycle 2) the fusion of the BPT renewal model (BPT+ΔCFF) with a physical model that considers the earthquake probability perturbation for interacting faults by static Coulomb stress changes. To do so, we calculate the probability of occurrence of earthquakes Mw > 6.5 for individual fault sources in the Marmara region for the 5-10-30 and 50-year periods (starting from January 1, 2013). We treat the uncertainties in the fault parameters (e.g. slip rate, characteristic magnitude and aperiodicity) of the statistical distribution associated to each examined fault source by a Monte Carlo technique. Then the probabilities of occurrence for the next characteristic earthquake are calculated from three different models (Poisson, BPT, and BPT+ΔCFF) considering the 10th, 50th and 90th percentiles of the Monte Carlo distribution.
In order to evaluate the impact of the earthquake probability models to ground motion hazard we attempt to calculate the fault-based probabilistic seismic hazard maps (PSHA) of mean Peak Ground Acceleration (PGA) having 10% probability of exceedance in 50 years on rock site condition. We note that in the present study we did not take in to account the ground motion variability caused by the different GMPE choices. In fact only one GMPE model is chosen as defined by Akkar and Cagnan (2010) (hereafter, AC10) for the active shallow crustal region for assessing the ground shaking hazard in the Marmara region in order to avoid those variability’s effect the final seismic hazard estimations in the study region.
We observed that the impact of the different occurrence models on the seismic hazard estimate of selected sites is quite high: the hazard may increase by more than 70% or decrease by as much as 70%, depending on the applied model. We demonstrated that the estimated average recurrence time and the associated magnitude together with the elapsed time are crucial parameters in the earthquake probability calculations.
Wed, 01 Jan 2014 00:00:00 GMThttp://hdl.handle.net/2122/109632014-01-01T00:00:00Z
- Simulating earthquake scenarios in the European Project LESSLOSS: the case of the metropolitan area of Lisbon (MAL)http://hdl.handle.net/2122/1825Title: Simulating earthquake scenarios in the European Project LESSLOSS: the case of the metropolitan area of Lisbon (MAL)
Authors: Zonno, G.; Akinci, A.; Cultrera, G.; Franceschina, G.; Pacor, F.; Pessina, V.; Cocco, M.; Carvalho, A.; Coelho, E.; Campos Costa, A.
Editors: Koller, M.; Giardini, D.
Abstract: In the framework of the ongoing European project “LESSLOSS – Risk Mitigation for Earthquakes and Landslides” two sub-projects are devoted to earthquake disaster scenario predictions and loss modeling for urban areas and infrastructures. This paper is dealing with the sub-project 10, SP10, Task Programme “Scenario earthquake definitions for three cities”. Finite-fault seismological models are proposed to compute the earthquake scenarios for three urban areas – Istanbul (Turkey), Lisbon (Portugal) and Thessaloniki (Greece). For each case study, ground motion scenarios are developed for the most probable two events with different return periods, locations and magnitudes derived from historical and geological data. In this study, we simulate the accelerometric time series and response spectra for high frequency ground motion in the city of Lisbon and surrounding counties (Metropolitan Area of Lisbon), using two possible earthquake models: the inland source area of Lower Tagus Valley, M 5.7 (4.7) and a hypothesis of the offshore source area of the 1755 Lisbon, M 7.6. The non-stationary stochastic method RSSIM (Carvalho et al. 2004) and a new hybrid stochastic-deterministic approach, DSM (Pacor et al., 2005) are used in order to evaluate the ground shaking and to characterize its spatial variability. Then the site effects are evaluated by means of an equivalent stochastic non-linear one-dimensional ground response analysis of stratified soil profile units properly designed. Results are here presented in terms of PGA maps, for offshore and inland scenarios. The mean and worst shaking scenarios for the Metropolitan Area of Lisbon have been delineated at the bedrock. Local effects amplify the synthetic PGA values by approximately a factor of 2. This means that PGA values computed for bedrock in Lisbon city can increase from 0.12g up to 0.25g and up to 0.5g in surroundings, for the inland scenario, and from 0.045g up to 0.090g for a M7.6 offshore scenario.
Sun, 03 Sep 2006 00:00:00 GMThttp://hdl.handle.net/2122/18252006-09-03T00:00:00Z
- Time Variability of crustal attenuation during the Amatrice-Visso-Norcia earthquake sequence in the Central Apennines (Italy)http://hdl.handle.net/2122/11926Title: Time Variability of crustal attenuation during the Amatrice-Visso-Norcia earthquake sequence in the Central Apennines (Italy)
Authors: Munafò, Irene; Malagnini, Luca; Sebastiani, Giovanni; Dreger, Douglas Scott; Akinci, Aybige; Burgmann, Roland
Abstract: Over the last decade our work has been mostly about reducing uncertainties over spectral
measurements in seismology (e.g. Malagnini and Munafò, 2018; Malagnini and Dreger, 2016;
Munafò et al., 2016; Akinci et al., 2014). Here we measure time-domain peak values from
narrow bandpass-filtered time histories and transform them into spectral estimates by using the
theoretical results of Random Vibration Theory (Cartwright and Longuet-Higgins, 1956) and the
Parseval Theorem. We develop a novel approach to quantify time domain fluctuations of highfrequency
seismic attenuation and apply it to a massive data set of seismic waveforms from the
Central Apennines in Italy, which includes recordings spanning the recent earthquake sequence
of Amatrice-Visso-Norcia (2016-2017). Our observations show that the crustal seismic wave
propagation in the region is strongly affected by transients triggered by the main events. The
time varying attenuation is probably due to the associated migration of crustal fluids, in addition
to seasonal oscillations related to precipitation-induced variations of crustal stresses. We also
observe oscillation periods in the attenuation time series corresponding to solid Earth tides.
Sensitivity to tides is stronger in the aftermath of the mainshocks, indicating an important role
played by rock damage.
Mon, 10 Dec 2018 00:00:00 GMThttp://hdl.handle.net/2122/119262018-12-10T00:00:00Z
- Strong Ground Motion Characteristics from the 17 August 1999 Kocaeli, Turkey earthquake.http://hdl.handle.net/2122/3764Title: Strong Ground Motion Characteristics from the 17 August 1999 Kocaeli, Turkey earthquake.
Authors: Akinci, A.
Abstract: The 17 August 1999 Kocaeli, Turkey earthquake, (Mw=7.4, USGS) occurred in the western part of the North Anatolian Fault Zone (NAFZ) about 80 km east of Istanbul. The mechanism of the main event was almost a pure right-lateral strike slip, and the aftershock distribution indicates that the rupture was located toward the western end of the NAFZ, (Taymaz, 1999, 2000). The earthquake affected a wide area in the Marmara region, as well as the city of Istanbul. Most of the damage and fatalities occurred in towns located on the narrow, flat shoreline of the Sea of Marmara. Since the broken fault segment traversed the densely populated and industrialized east Marmara region, damage was enormously high. Widespread liquefactions caused bearing capacity losses and consequent foundation failures in the Adapazari region, as well as extensive subsidence along the shoreline in Gölcük (Gulf of Izmit) and Sapanca. The earthquake struck also the western suburbs of Istanbul, the Avcilar region, causing severe damage on buildings even though the distance from the epicenter was about 80 km, (Cranswick, et al., 2000).
In this study, we discuss the ground motion characteristics, as well as directivity and soil effects of recorded ground acceleration of the Kocaeli earthquake. Strong-motion data were obtained from the networks managed by the Bogaziçi University, Kandilli Observatory & Earthquake Research Institute, (KOERI) and by the General director of Disaster Affairs, Earthquake Research Department, (ERD). Although the distribution of the accelerometers deployed in the epicentral area seems sparse, the Izmit earthquake generated approximately twenty strong-motion records within 200 km of the fault. Maximum Peak Ground Acceleration (PGA) has reached 0.41g in Adapazarı, SKR, 40 km east from the epicenter and 3 km far from the fault rupture. This value is rather small, only half of the value observed in various large earthquakes, e.g., 0.8g in the 1995 Kobe, Japan earthquake and 0.9g in the 1999 Chi-Chi, Taiwan, earthquake, while the maximum ground velocity was about 0.8 m/s, that is comparable to the typical value observed in large earthquakes, (Yagi & Kikuchi, 2000).
Tue, 01 Jan 2002 00:00:00 GMThttp://hdl.handle.net/2122/37642002-01-01T00:00:00Z
- HAZGRIDX: earthquake forecasting model for ML ≥ 5.0 earthquakes in Italy based on spatially smoothed seismicityhttp://hdl.handle.net/2122/6698Title: HAZGRIDX: earthquake forecasting model for ML ≥ 5.0 earthquakes in Italy based on spatially smoothed seismicity
Authors: Akinci, A.
Abstract: We present a five-year, time-independent, earthquake-forecast model for earthquake magnitudes of 5.0 and greater in Italy using spatially smoothed seismicity data. The model is called HAZGRIDX, and it was developed based on the assumption that future earthquakes will occur near locations of historical earthquakes; it does not take into account any information from tectonic, geological, or geodetic data. Thus HAZGRIDX is based on observed earthquake occurrence from seismicity data, without considering any physical model. In the present study, we calculate earthquake rates on a spatial grid platform using two declustered catalogs: 1) the Parametric catalog of Italian earthquakes (Catalogo Parametrico dei Terremoti Italiani, CPTI04) that contains the larger earthquakes from MW 7.0 since 1100; and 2) the Italian seismicity catalogue (Catalogo della Sismicità Italiana, CSI 1.1) that contains the small earthquakes down to ML 1.0, with a maximum of ML 5.9, over the past 22 years (1981-2003). The model assumes that earthquake magnitudes follow the Gutenberg-Richter law, with a uniform b-value. The forecast rates are presented in terms of the expected numbers of ML>5.0 events per year for each grid cell of about 10 km × 10 km. The final map is derived by averaging the earthquake potentials that come from these two different catalogs: CPTI04 and CSI 1.1. We also describe the earthquake occurrences in terms of probabilities of occurrence of one event within a specified magnitude bin, DM0.1, in a five year time period. HAZGRIDX is one of several forecasting models, scaled to five and ten years, that have been submitted to the Collaboratory for the Study of Earthquake Probability (CSEP) forecasting center in ETH, Zurich, to be tested for Italy.
Fri, 25 Jun 2010 00:00:00 GMThttp://hdl.handle.net/2122/66982010-06-25T00:00:00Z
- When time and faults matter: towards a time-dependent probabilistic SHA in Calabria, Italyhttp://hdl.handle.net/2122/10580Title: When time and faults matter: towards a time-dependent probabilistic SHA in Calabria, Italy
Authors: Akinci, Aybige; Vannoli, Paola; Falcone, G.; Taroni, M.; Tiberti, Mara Monica; Murru, Maura; Burrato, Pierfrancesco; Mariucci, Maria Teresa
Abstract: In this study, we attempt to improve the standards in Probabilistic Seismic Hazard Assessment (PSHA) towards a time-dependent hazard assessment by using the most advanced methods and new databases for the Calabria region, Italy. In this perspective we improve the knowledge of the seismotectonic framework of the Calabrian region using geologic, tectonic, paleoseismological, and macroseismic information available in the literature. We built up a PSHA model based on the long-term recurrence behavior of seismogenic faults, together with the spatial distribution of historical earthquakes. We derive the characteristic earthquake model for those sources capable of rupturing the entire fault segment (full-rupture) independently with a single event of maximum magnitude. We apply the floating rupture model to those earthquakes whose location is not known sufficiently constrained. We thus associate these events with longer fault systems, assuming that any such earthquake can rupture anywhere within the particular fault system (floating partial-rupture) with uniform probability. We use a Brownian Passage Time (BPT) model characterized by mean recurrence, aperiodicity, or uncertainty in the recurrence distribution and elapsed time since the last characteristic earthquake. The purpose of this BPT model is to express the time-dependence of the seismic processes to predict the future ground motions in the region. Besides, we consider the influence on the probability of earthquake occurrence controlled by the change in static Coulomb stress (ΔCFF) due to fault interaction; to pursue this, we adopt a model built on the fusion of BPT model (BPT + ΔCFF). We present our results for both time-dependent (renewal) and time-independent (Poisson) models in terms of Peak Ground Acceleration (PGA) maps for 10% probability of exceedance in 50 years. The hazard may increase by more than 20% or decrease by as much as 50% depending on the different occurrence model. Seismic hazard in terms of PGA decreases about 20% in the Messina Strait, where a recent major earthquake took place, with respect to traditional time-independent estimates. PGA near the city of Cosenza reaches ~ 0.36 g for the time-independent model and 0.40 g for the case of the time-dependent one (i.e. a 15% increase). Both the time-dependent and time-independent models for the period of 2015–2065 demonstrate that the city of Cosenza and surrounding areas bear the highest seismic hazard in Calabria.
Sun, 01 Jan 2017 00:00:00 GMThttp://hdl.handle.net/2122/105802017-01-01T00:00:00Z
- Il terremoto di Haiti del 12 Gennaio 2010 (Mw 7.0)http://hdl.handle.net/2122/6701Title: Il terremoto di Haiti del 12 Gennaio 2010 (Mw 7.0)
Authors: Akinci, A.; Malagnini, L.
Abstract: Il terremoto di Haiti del 12 gennaio 2010 (Mw 7.0) si
è verificato alle ore 16:53:09 locali (21:53:09 UTC).
L’epicentro è stato localizzato a circa 25 chilometri da
Port-au-Prince, la capitale, con una profondità ipocentrale
di 13 km (fonte United States Geological Survey,
USGS). USGS ha localizzato sei repliche nelle due ore
successive al terremoto principale, di magnitudo compresa
tra 4.5 e 5.9. (5.9, 5.5, 5.1, 4.8, 4.5, e 4.5). Nelle prime
nove ore successive all’evento principale, sono state registrate
26 repliche di magnitudo M ≥ 4.2, dodici delle quali
di magnitudo M ≥ 5.0.
Mon, 01 Mar 2010 00:00:00 GMThttp://hdl.handle.net/2122/67012010-03-01T00:00:00Z
- Prediction of High-Frequency Ground Motion Parameters Based on Weak Motion Datahttp://hdl.handle.net/2122/7984Title: Prediction of High-Frequency Ground Motion Parameters Based on Weak Motion Data
Authors: D'Amico, S.; Akinci, A.; Malagnini, L.; Galea, P.
Abstract: Large earthquakes that have occurred in recent years in densely populated areas of the world
(e.g. Izmit, Turkey, 17 August 1999; Duzce, Turkey, 12 November 1999; Chi-Chi, Taiwan 20
September 1999, Bhuj, India, 26 January 2001; Sumatra 26 December 2004; Wenchuan, China,
May 12, 2008; L’Aquila, Italy, April 6, 2009; Haiti, January 2010 Turkey 2011) have dramatically
highlighted the inadequacy of a massive portion of the buildings erected in and around the
epicentral areas. For example, the Izmit event was particularly destructive because a large
number of buildings were unable to withstand even moderate levels of ground shaking,
demonstrating poor construction criteria and, more generally, the inadequacy of the
application of building codes for the region. During the L’Aquila earthquake (April, 06, 2009;
Mw=6.3) about 300 persons were killed and over 65,000 were left homeless (Akinci and
Malagnini, 2009). It was the deadliest Italian earthquake since the 1980, Irpinia earthquake, and
initial estimates place the total economic loss at over several billion Euros. Many studies have
already been carried out describing the rupture process and the characteristics of local site
effects for this earthquake (e.g. D’Amico et al., 2010a; Akinci et al., 2010). It has been observed
that many houses were unable to withstand the ground shaking.
Building earthquake-resistant structures and retrofitting old buildings on a national scale may
be extremely costly and may represent an economic challenge even for developed western
countries, but it is still a very important issue (Rapolla et al., 2008). Planning and design should
be based on available national hazard maps, which, in turn, must be produced after a careful
calibration of ground motion predictive relationships (Kramer, 1996) for the region.
Consequently, the assessment of seismic hazard is probably the most important contribution
of seismology to society. The prediction of the earthquake ground motion has always been
of primary interest for seismologists and structural engineers. For engineering purposes it is
necessary to describe the ground motion according to certain number of ground motion
parameters such as: amplitude, frequency content and duration of the motion. However it is
necessary to use more than one of these parameters to adequately characterize a particular
ground motion.
Updating existing hazard maps represents one of the highest priorities for seismologists,
who contribute by recomputing the ground motion and reducing the related uncertainties.
The quantitative estimate of the ground motion is usually obtained through the use of the so-called predictive relationships (Kramer, 1996), which allow the computation of specific
ground-motion parameter as a function of magnitude, distance from the source, and
frequency and they should be calibrated in the region of interest. However this is only
possible if seismic records of large earthquakes are available for the specific region in order
to derive a valid attenuation relationship regressing a large number of strong-motion data
(e.g. Campbell and Bozorgnia, 1994; Boore et al., 1993; Ambraseys et al., 1996, Ambraseys
and Simpson, 1996; Sabetta and Pugliese, 1987, 1996; Akkar and Bommer 2010). For the
Italian region the most used attenuation relationships are those obtained by Sabetta and
Pugliese (1987, 1996) regressing a few data recorded for earthquakes in different tectonic
and geological environments. It has been shown in several cases that it is often not adequate to
reproduce the ground motion in each region of the country using a single model. Furthermore
the different crustal properties from region to region play a key role in this kind of studies.
However, the attenuation properties of the crust can be evaluated using the background
seismicity as suggested by Chouet et al. (1978) and later demonstrated by Raoff et al. (1999)
and Malagnini et al (2000a, 2007). In other words, it becomes possible to develop regionallycalibrated
attenuation relationships even where strong-motion data are not available. One of
the purposes of this work is to describe quantitatively the regional attenuation and source
characteristics for constraining the amplitude of strong motion expected from future
earthquakes in the area. In this work we describe how to use the background seismicity to
perform the analysis (details in Malagnini et. 2000a, 2007). In particular, this chapter describes
the procedures and techniques to study the ground motion and will focus on describing both
strong motion attenuation relationships and the techniques used to derive the ground motion
parameters even when strong ground motion data are not available. We will present the
results obtained for different regions of the Italian peninsula, showing that the attenuation
property of the crust and of the source can significantly influence the ground motion. In
addition, we will show that stochastic finite-fault modeling based on a dynamic frequency
approach, coupled with field investigations, confirms to be a reliable and practical method to
simulate ground motion records of moderate and large earthquakes especially in regions
prone to widespread structural damage.
Sun, 01 Jan 2012 00:00:00 GMThttp://hdl.handle.net/2122/79842012-01-01T00:00:00Z
- Deliverable # D3.01.4 Probability of occurrence for earthquakes generated by individual faults and the associated uncertaintieshttp://hdl.handle.net/2122/6464Title: Deliverable # D3.01.4 Probability of occurrence for earthquakes generated by individual faults and the associated uncertainties
Authors: Basili, R.; Akinci, A.
Abstract: Probabilities and uncertainties were calculated based on the approach developed by Akinci et al. (2008). The method was applied to the whole Italian territory using a dataset that integrates individual seismogenic sources derived from both geological/geophysical data and macroseismic data (see Basili et al., 2008, for definitions). We designed two model approaches: one that uses geological slip rates; another that uses slip rates derived from the finite element model developed by Barba et al, 2007. As for recurrence we adopted the Poisson and the Renewal BPT models with aperiodicity a equal to 0.3, 0.5 and 0.7, all for a prediction in the next 30 years. Complete results of these procedures are given in tabular form at the end of this document.
Sun, 30 May 2010 00:00:00 GMThttp://hdl.handle.net/2122/64642010-05-30T00:00:00Z
- Characteristics of the Strong Ground Motion from the 24th August 2016 Amatrice Earthquakehttp://hdl.handle.net/2122/11429Title: Characteristics of the Strong Ground Motion from the 24th August 2016 Amatrice Earthquake
Authors: Pischiutta, Marta; Akinci, Aybige; Malagnini, Luca; Herrero, André
Abstract: The 2016 August 24 Amatrice earthquake occurred at 03:36 local time in Central Apennines Italy with an epicentre at
43.36°E, 38.76°N, Istituto Nazionale di Geofisica e Vulcanologia (INGV), few kilometers north of the city of Amatrice.
The earthquake ruptured a North-West (NW)–South-East (SE) oriented normal fault dipping toward the South-West
(SW) (Scognamiglio et al., 2016). High values of peak ground acceleration (~0.92 g) were observed close to Amatrice (3
stations being few kilometer distances from the fault). The present study presents an overview of the main features of the
seismic ground shaking during the Amatrice earthquake. We analyze the ground motion characteristics of the main
shock in terms of peak ground acceleration (PGA), peak ground velocity (PGV) and spectral accelerations (SA, 5 per
cent of critical damping). In order to understand the characteristics of the ground motions induced by Amatrice earthquake,
we also study the source-related effects relative to the fault rupture directivity.
Fri, 01 Jan 2016 00:00:00 GMThttp://hdl.handle.net/2122/114292016-01-01T00:00:00Z
- Uncertainties in probability of occurrence of strong earthquakes for fault sources in the Central Apennines, Italyhttp://hdl.handle.net/2122/6704Title: Uncertainties in probability of occurrence of strong earthquakes for fault sources in the Central Apennines, Italy
Authors: Akinci, A.; Perkins, D.; Lombardi, A. M.; Basili, R.
Abstract: Using the characteristic earthquake
model, we calculate the probability of occurrence
of earthquakes Mw > 5.5 for individual fault
sources in the Central Apennines for the 30-year
period (2007–2037). We show the effect of timedependent
and time-independent occurrence
(Brownian passage time (BPT) and Poisson) models
together with uncertain slip rates and uncertain
maximum magnitudes and, hence, uncertain
recurrence times. In order to reduce the large
prior geological slip rate uncertainty distribution
for most faults, we obtain a posterior slip rate
uncertainty distribution using a likelihood function
obtained from regional historical seismicity.
We assess the uncertainty of maximum magnitude
by assuming that the uncertainty in fault width
and length are described by a normal distribution
with standard deviation equal to ±20% of the
mean values. We then estimate the uncertainties
of the 30-year probability of occurrence of a characteristic event using a Monte Carlo procedure.
Uncertainty on each parameter is represented
by the 16th and the 84th percentiles of
simulated values. These percentiles bound the
range that has a 68% probability of including the
real value of the parameter. We do these both for
the Poisson case and for the BPT case by varying
the aperiodicity parameter (α value) using the
values 0.3, 0.5, and 0.7. The Bayesian posterior
slip rate uncertainties typically differ by a factor
of about 2 from the 16th to the 84th percentile.
Occurrence probabilities for the next 30 years at
the 84th percentile typically range from 1% to
2% for faults where the Poisson model dominates
and from 2% to 21% where one of the BPT
models dominates. The uncertainty in occurrence
probability under the time-dependent hypothesis
is very large, when measured by the ratio of the
84th to the 16th percentile, frequently being as
much as two orders of magnitude. On the other
hand, when measured by standard deviation,
these standard deviations range from 2% to 6%
for those faults whose elapsed time since previous
event is large, but always 2% or less for faults with
relatively recent previous occurrence, because the
probability of occurrence is always small.
Fri, 01 Jan 2010 00:00:00 GMThttp://hdl.handle.net/2122/67042010-01-01T00:00:00Z
- Imaging the rupture of the Mw 6.3 April 6, 2009 L’Aquila, Italy earthquake using back‐projection of teleseismic P‐waveshttp://hdl.handle.net/2122/6699Title: Imaging the rupture of the Mw 6.3 April 6, 2009 L’Aquila, Italy earthquake using back‐projection of teleseismic P‐waves
Authors: D'Amico, S.; Koper, K.; Herrmann, R. B.; Akinci, A.; Malagnini, L.
Abstract: We present rupture details of the Mw 6.3 April 6, 2009
L’Aquila earthquake derived by back‐projecting teleseismic
P waves. This technique has previously been applied to large
magnitude earthquakes, but this is the first application to a
moderate size event. We processed vertical‐component
seismograms for 60 broadband stations obtained from the
Incorporated Research Institutions for Seismology (IRIS)
data center. The traces were aligned and normalized using
a multi‐channel cross‐correlation algorithm and 4th root
stacking was used to image the rupture. We found that the
L’Aquila earthquake ruptured towards the south and that a
second discrete pulse of energy occurred 20–25 km east
of the epicenter about 17–18 s after the nominal origin
time. The spatial extent of the rupture image correlates
well with a post‐seismic survey of damage in the region.
Because the technique is potentially very fast (images can
be produced within 20–30 minutes of the origin time), it
may be useful to governmental agencies tasked with
emergency response and rescue.
Mon, 01 Feb 2010 00:00:00 GMThttp://hdl.handle.net/2122/66992010-02-01T00:00:00Z
- Characterization of earthquake-induced ground motion from the L’Aquila seismic sequence of 2009, Italyhttp://hdl.handle.net/2122/6700Title: Characterization of earthquake-induced ground motion from the L’Aquila seismic sequence of 2009, Italy
Authors: Malagnini, L.; Akinci, A.; Mayeda, K.; Munafo, I.; Herrmann, R. B.; Mercuri, A.
Abstract: Based only on weak-motion data, we carried out a combined study on region-specific source
scaling and crustal attenuation in the Central Apennines (Italy). Our goal was to obtain a
reappraisal of the existing predictive relationships for the ground motion, and to test them
against the strong-motion data [peak ground acceleration (PGA), peak ground velocity (PGV)
and spectral acceleration (SA)] gathered during the Mw 6.15 L’Aquila earthquake (2009 April
6, 01:32 UTC). The L’Aquila main shockwas not part of the predictive study, and the validation
test was an extrapolation to one magnitude unit above the largest earthquake of the calibration
data set.
The regional attenuation was determined through a set of regressions on a data set of
12 777 high-quality, high-gain waveforms with excellent S/N ratios (4259 vertical and 8518
horizontal time histories). Seismograms were selected from the recordings of 170 foreshocks
and aftershocks of the sequence (the complete set of all earthquakes with ML ≥ 3.0, from
2008 October 1 to 2010 May 10). All waveforms were downloaded from the ISIDe web
page (http://iside.rm.ingv.it/iside/standard/index.jsp), a web site maintained by the Istituto
Nazionale di Geofisica e Vulcanologia (INGV).
Weak-motion data were used to obtain a moment tensor solution, as well as a coda-based
moment-rate source spectrum, for each one of the 170 events of the L’Aquila sequence (2.8 ≤ Mw ≤ 6.15). Source spectra were used to verify the good agreement with the source scaling of
the Colfiorito seismic sequence of 1997–1998 recently described by Malagnini et al. (2008).
Finally, results on source excitation and crustal attenuationwere used to produce the absolute
site terms for the 23 stations located within ∼80 km of the epicentral area. The complete set
of spectral corrections (crustal attenuation and absolute site effects) was used to implement
a fast and accurate tool for the automatic computation of moment magnitudes in the Central
Apennines.
Sat, 01 Jan 2011 00:00:00 GMThttp://hdl.handle.net/2122/67002011-01-01T00:00:00Z
- Strong evidence for non-similar earthquake source scaling in central Italyhttp://hdl.handle.net/2122/4218Title: Strong evidence for non-similar earthquake source scaling in central Italy
Authors: Malagnini, L.; Scognamiglio, L.; Mercuri, A.; Akinci, A.; Mayeda, K.
Abstract: scaling of seismic sources of the Central Apennines (Italy) is investigated using broadband seismograms from the Colfiorito sequence (4<=Mw<=6 ). Our results are not consistent with self-similar scaling, and can be described by the following relationship: M0~fc^-(3_epsilon), where epsilon=1.7+-0.3 . We speculate that dynamic fault lubrication by fluid pressurization may be responsible for such extreme behavior, and use our results for the calibration of a weak-motion-based predictive relationship for the ground motion ( Mw<=4.1) up to Mw~6 for this region.
Tue, 01 Jan 2008 00:00:00 GMThttp://hdl.handle.net/2122/42182008-01-01T00:00:00Z
- Effect of time-dependence on probabilistic seismic hazard maps and deaggregation for the Central Apennines, Italyhttp://hdl.handle.net/2122/5590Title: Effect of time-dependence on probabilistic seismic hazard maps and deaggregation for the Central Apennines, Italy
Authors: Akinci, A.; Galadini, F.; Pantosti, D.; Petersen, M.; Malagnini, L.; Perkins, D.
Abstract: We produce probabilistic seismic hazard assessments for the Central Apennines, Italy, using time-dependent models that are characterized using a Brownian Passage Time (BPT) recurrence model. Using aperiodicity parameters, of 0.3, 0.5, and 0.7, we examine the sensitivity of the probabilistic ground motion and its deaggregation to these parameters. For the seismic source model we incorporate both smoothed historical seismicity over the area and geological information on faults. We use the maximum magnitude model for the fault sources together with a uniform probability of rupture along the fault (floating fault model) to model fictitious faults to account for earthquakes that cannot be correlated with known geologic structural segmentation. We show maps for peak ground acceleration (PGA) and 1.0-Hz spectral acceleration (SA1) on rock having 10% probability of exceedence (PE) in 50 years. We produce maps to compare the separate contributions of smoothed seismicity and fault components. In addition we construct maps that show sensitivity of the hazard for different parameters and the Poisson model. For the Poisson model, the addition of fault sources to the smoothed seismicity raises the hazard by 50 % at locations where the smoothed seismicity contributes the highest hazard, and up to 100 % at locations where the hazard from smoothed seismicity is low. For the strongest aperiodicity parameter (smallest ), the hazard may further increase 60-80 % or more or may decrease by as much as 20 %, depending on the recency of the last event on the fault that dominates the hazard at a given site. In order to present the most likely earthquake magnitude and/or the most likely source-site distance for scenario studies, we deaggregate the seismic hazard for SA1 and PGA for two important cities (Roma and l’Aquila) . For PGA, both locations show the predominance of local sources, having magnitudes of about 5.3 and 6.5 respectively. For SA1 at a site in Rome, there is significant contribution from local smoothed seismicity, and an additional contribution from the more distant Apennine faults having magnitude around 6.8. For l’Aquila, the predominant sources remain local. In order to show the variety of impact of different values we also obtained deaggregations for another three sites. In general, as decreases (periodicity increases), the deaggregation indicates that the hazard is highest near faults with the highest earthquakes rates. This effect is strongest for the long-period (1 s) ground motions.
Wed, 01 Apr 2009 00:00:00 GMThttp://hdl.handle.net/2122/55902009-04-01T00:00:00Z
- Prediction of Ground Motion and Loss Scenarios for Selected Infrastructues Systems in European Urban Environmentshttp://hdl.handle.net/2122/3227Title: Prediction of Ground Motion and Loss Scenarios for Selected Infrastructues Systems in European Urban Environments
Authors: Faccioli, E.; Callerio, A.; Ameri, G.; Zonno, G.; Pacor, F.; Akinci, A.; Cultrera, G.; Cocco, M.; Franceschina, G.; Pessina, V.; Lombardi, A. M.; Pitilakis, K.; Kakderi, K.; Alexaudi, M.; Kim, S.; Ansal, A.; Erdik, M.; Tonuk, G.; Dermircioglu, M.; Paolucci, R.; Scandella, L.
Abstract: computational tools needed for developing scenarios of earthquake ground motions and
of ensuing damage to representative urban Infrastructure Systems (IS), as well as with
illustrative examples of application to cities in Europe and neighbouring countries. The
material illustrated is the outcome of the work carried out in LESSLOSS Sub-Project
SP11, devoted to the title subject. Of main concern are the water and natural gas
distribution networks and the sewage networks, because these are, with the transportation
network, by far the most extensive IS in cities and, especially the first one, often the most
vulnerable. Also, emphasis is placed more on the tools for achieving a scenario and on
their application, rather than on the economic loss evaluation. As a partial justification of
the belated development and interest in seismic IS damage, it is recalled that destructive
earthquakes of recent decades in Europe did not cause large scale damage to IS.
In addition to describing tools for the practical construction of damage scenarios for IS,
the report also highlights some innovative research trends in the field, especially the
methods leading to the estimation of pipeline damage on the basis of the peak ground
strains generated by the propagation of seismic waves, which in turn needs the support of
advanced 2D or 3D wave propagation modelling.
The main sections of the report are devoted to:
- Calculation of seismic ground motions in an area, both of advanced and
simplified engineering level, with applications for Thessaloniki and Düzce (Sect
2);
- Outline of the buried pipelines response during earthquakes, illustrating the chief
elements at play on the side of the seismic loading effects and typical damage
(Sect. 3);
- Vulnerability representations for IS components, mostly those consisting of
buried pipelines (Sect. 4);
- Typical features of IS inventories, with examples (Sect 5);
- Damage evaluation tools at urban scenario and single pipeline level (Sect. 6);
- Damage scenario applications for Thessaloniki and Düzce (Sect 7);
- Conclusions.
Sun, 01 Jul 2007 00:00:00 GMThttp://hdl.handle.net/2122/32272007-07-01T00:00:00Z
- The 2012 Ferrara seismic sequence: from a 1D reliable crustal structure for moment tensor solutions to strong implications for seismic hazardhttp://hdl.handle.net/2122/8992Title: The 2012 Ferrara seismic sequence: from a 1D reliable crustal structure for moment tensor solutions to strong implications for seismic hazard
Authors: Munafò, Irene; Malagnini, Luca; Buttinelli, Mauro; Herrmann, R. B.; Anselmi, Mario; Akinci, Aybige; Boschi, Enzo
Abstract: On May 20 2012, an event of Ml 5.9 (Mw 5.6) stuck the southem edge of the Po river plain (Pianura Padana). The earthquake was preceded by a foreshock of Ml 4.1 (Mw 3.8), less than 3 hours before the Mw 5.6 main. Hypocentral depths were 6.3 km for both events. Centroid depths were 5 and 6 km, respectively. The activated fault was a reverse one, dipping to the south. Then a complex seismic sequence started, in which more than six earthquakes with Ml greater than 5 stuck the area, the last one on June 3, 2012. Aftershocks delineated a 50 km long and 10-15 km wide zone, approximately elongated in the WE direction. More than 2100 events were located between May 19 and June 25 2012 by the INGV National Seismic Network, 80 of them with Ml greater than 3.5. The damage due to the Ml 5+ earthquakes was widespread, as they severely hit historical towns and industrial infrastructures. However, a striking inconsistency exists between the relatively small moment magnitudes and the corrisponding high level of damage. In order to define a velocity structure for the crust beneath the Pianura Padana, to be used for waveform inversion of moment tensors, we gathered all the geophysical and geological information available for the area. The model is characterized by very thick and shallow Quaternary sediments, to be used for the inversion of broadband waveforms for moment tensor (MT) solutions, in the frequency band between 0.02-0.1 Hz. We calculated moment tensors for 20 events down to Mw~3.2. We demonstrate how surface waves dominate the seismograms in the region, which may have played a major role in enhancing the damage to industrial structures observed in the epicentral area. Synthetic seismograms computed using the developed model well reproduced the anomalous durations of the ground motion observed in Pianura Padana, also highlighting important implications for the seismic hazard in the entire area. The present seismic hazard assessment as well as the size of the historical earthquakes in the region (and so their recurrence times), may need to be re-evaluated in the light of this new results.
Wed, 25 Sep 2013 00:00:00 GMThttp://hdl.handle.net/2122/89922013-09-25T00:00:00Z
- Characteristics of the strong ground motions from the 6 April 2009 L’Aquilahttp://hdl.handle.net/2122/5887Title: Characteristics of the strong ground motions from the 6 April 2009 L’Aquila
Authors: Akinci, A.; Malagnini, L.; Sabetta, F.
Abstract: An Mw 6.25 earthquake occurred on April 6, 2009 at 03:33 a.m. local time, in the Abruzzo region (Central Italy), close to the city of L’Aquila. The earthquake ruptured a North-West (NW)-South-East (SE) oriented normal fault dipping toward the South-West (SW), with the city of L’Aquila lying a few kilometers away on the hanging wall.
The main shock has been recorded by fifty-eight accelerometric stations: the highest number of digital recordings ever obtained in Italy for a single earthquake, one of the best-recorded earthquakes with a normal fault mechanism. Very high values of peak ground acceleration (0.3-0.65g) were observed close to the center of L’Aquila (6 stations at zero JB distance from the fault). The earthquake caused severe loss of lives (299 victims and 1500 injured) and damage (about 18000 unusable buildings) in the epicentral area.
In this study we analyze the ground motion characteristics of both the main shock in terms of peak ground acceleration (PGA), peak ground velocity (PGV), and pseudo-acceleration response spectra (5% of damping ratio). In particular, we compare the pseudo-acceleration response spectra for horizontal directions with the EC8 design spectrum and the new Italian building code (NTC08). In order to understand the characteristics of the ground motions induced by L’Aquila earthquake, we also study the source-related effects and site response of the strong motion stations that recorded the seismic sequence. A novel method is used for the analysis of inter-station and site-specific H/V spectral ratios for the main event and for 12 aftershocks.
Fri, 01 Jan 2010 00:00:00 GMThttp://hdl.handle.net/2122/58872010-01-01T00:00:00Z
- Predictions of high-frequency ground-motion in Taiwan based on weak motion datahttp://hdl.handle.net/2122/7985Title: Predictions of high-frequency ground-motion in Taiwan based on weak motion data
Authors: D'Amico, S.; Akinci, A.; Malagnini, L.
Abstract: Following a recent paperwe useweak-motionwaveforms to calibrate a model for the prediction
of earthquake-induced ground-motion in Taiwan, in the 0.25–5.0 Hz frequency range, valid up
to Mw 7.6. The excitation/attenuation model is given in terms of frequency-dependent seismic
wave attenuation, Qs(f ), geometrical spreading, g(r), amagnitude-dependent stress parameters
σ for the excitation terms, and a site term for each seismic station used in the study. A set
of weak-motion data was gathered from about 170 aftershocks of the Chi–Chi earthquake,
Mw 7.6, of 1999 September 20, (17:47 UTC), recorded by 10 broad-band seismic stations.
The moment magnitudes of the registered aftershocks ranged from Mw 3.0 to 6.5, and the
hypocentral distances from a few kilometres to about 250 km. A frequency-dependent crustal
quality factor, Q(f ) = 350f 0.32, was obtained, to be coupled with the geometrical spreading
function
g (r ) =
⎧⎪
⎪⎨⎪
⎪⎩
r−1.2 1 < r < 10 km
r−0.7 10 < r < 40 km
r−1.0 40 < r < 80 km
r−0.5 r > 80 km.
Earthquake-related excitation spectra were calibrated over our empirical results by using a
magnitude-dependent Brune model with a stress drop value of σ = 8.0 ± 1.0 MPa for the
largest event of Mw 6.5 in our data set and with a near surface attenuation parameter of κ = 0.05 s.
Results on region-specific crustal attenuation and source scaling were used to generate
stochastic simulations both for point-source and extended-fault ruptures through the computer
codes: Stochastic Model SIMulation, SMSIM and Extended-FaultModel Simulation, EXSIM.
The absolute peak ground accelerations (PGA), peak ground velocities (PGV) and 5 per centdamped
Spectral Accelerations (SA) at three different frequencies, 0.33 Hz, 1.0 Hz and 3.0 Hz
for several magnitudes and distance ranges were predicted at large magnitudes, well beyond
magnitudeMw 6.5, the upper limit for the events of ourweak-motion data set. The performance
of the stochastic model was then tested against the strong-motion data recorded during the Mw
7.6 Chi–Chi earthquake, and against several other empirical ground-motion models.
Sun, 01 Jan 2012 00:00:00 GMThttp://hdl.handle.net/2122/79852012-01-01T00:00:00Z
- Separation of Source, Propagation and Site Effects from Observed S-wave of Bursa City and Its Vicinity in the Northwestern Anatolian Fault Zone, Turkeyhttp://hdl.handle.net/2122/3781Title: Separation of Source, Propagation and Site Effects from Observed S-wave of Bursa City and Its Vicinity in the Northwestern Anatolian Fault Zone, Turkey
Authors: Akyol, N.; Akinci, A.; Eyidogan, H.
Abstract: Micro and moderate-sized earthquake recordings (ML=1.8-4.1) of local events have been used to quantify attenuation and site effects in the vicinity of the Bursa City of Marmara region, Turkey. We used digital records from 69 local events recorded at short hypocentral distance (r < 60 km) in the region. The digital seismograms analyzed were recorded by temporary network of six seismic stations each of them deployed in a different geological site. Non-parametric inversion method was applied to acceleration records from tectonically active Bursa region and results obtained using a two-step inversion. At the first step, we determined attenuation functions by analyzing the distance dependence of the spectral amplitudes and retrieved values of Qs = 38.26f 0.73. The attenuation functions including anelasticity of heterogeneous medium and geometrical spreading effect were used to correct the S-wave spectral records. At the second step, the corrected amplitudes were inverted to separate source and site response for 21 different frequencies selected between 0.5 and ~25 Hz. The near surface attenuation was also estimated and found that the spectral decay parameter is smaller for stations located on rock, Igdır, (SIGD, ~0.006) compared to stations located on soft sediment, Hamitler, (SHMT, ~0.02). Çukurca, (SCKR) is the most important site having about 3.5 amplification value at 1.8 Hz. Demirtaş, (SDEM) amplifying the spectral amplitudes about 2.8 times at 2.5 Hz, SHMK about 3 times at between 2.5 and 3.5 Hz and SHMT about up to 3 times at between 1.5 and 4 Hz. However, stations located on the Uludağ Mountain Masif (SKAY and SIGD), which correspond to a deep Limestone geological unit, have the smallest amplification, that values between 0.6 and 1.4.
Tue, 01 Jan 2002 00:00:00 GMThttp://hdl.handle.net/2122/37812002-01-01T00:00:00Z
- A regional ground motion excitation/attenuation model for the San Francisco regionhttp://hdl.handle.net/2122/2913Title: A regional ground motion excitation/attenuation model for the San Francisco region
Authors: Malagnini, L.; Mayeda, K.; Uhrhammer, R.; Akinci, A.; Herrmann, R. B.
Abstract: By using small-to-moderate-sized earthquakes located within ~200 km of San Francisco, we characterize the scaling of the ground motions for frequencies ranging between 0.25 and 20 Hz, obtaining results for geometric spreading, Q(f), and site parameters using the methods of Mayeda et al. (2005) and Malagnini et al. (2004). The results of the analysis show that, throughout the Bay Area, the average regional attenuation of the ground motion can be modeled with a bilinear geometric spreading function with a 30 km crossover distance, coupled to an anelastic function exp(-pi*f*r/V*Q(f)) , where: Q(f)=180f^0.42. A body-wave geometric spreading, g(r)= r^-1.0, is used at short hypocentral distances (r < 30 km), whereas g(r)= r^-0.6 fits the attenuation of the spectral amplitudes at hypocentral distances beyond the crossover.
The frequency-dependent site effects at 12 of the Berkeley Digital Seismic Network (BDSN) stations were evaluated in an absolute sense using coda-derived source spectra.
Our results show: i) the absolute site response for frequencies ranging between 0.3 Hz and 2.0 Hz correlate with independent estimates of the local magnitude residuals (dML) for each of the stations; ii) moment-magnitudes (MW) derived from our path and site-corrected spectra are in excellent agreement with those independently derived using full-waveform modeling as well as coda-derived source spectra; iii) we use our weak-motion-based relationships to predict motions region wide for the Loma Prieta earthquake, well above the maximum magnitude spanned by our data set, on a completely different set of stations. Results compare well with measurements taken at specific NEHRP site classes; iv) an empirical, magnitude-dependent scaling was necessary for the Brune stress parameter in order to match the large magnitude spectral accelerations and peak ground velocities with our weak-motion-based model.
Fri, 01 Jun 2007 00:00:00 GMThttp://hdl.handle.net/2122/29132007-06-01T00:00:00Z
- Separation of depth-dependent intrinsic and scattering seismic attenuation in the northeastern sector of the Italian Peninsulahttp://hdl.handle.net/2122/409Title: Separation of depth-dependent intrinsic and scattering seismic attenuation in the northeastern sector of the Italian Peninsula
Authors: Bianco, F.; Del Pezzo, E.; Malagnini, L.; Di Luccio, F.; Akinci, A.
Abstract: We investigated the intrinsic dissipation and scattering properties of the lithosphere under the Friuli region (northeastern Italy) using two hypotheses: (i) a uniform earth model and (ii) wo 'reasonable' non-uniform, layered crustal models. For case (i) we measured the coda Q, and used the multiple-lapse time window analysis (MLTWA) technique to obtain separate estimates of intrinsic absorption and scattering attenuation. Results for the uniform earth model show that the lithosphere in northeastern Italy is characterized by a low-scattering attenuation (small scattering Q-inverse, Q1s), and by a relatively high intrinsic attenuation (high intrinsic Q-inverse, Q1i). A comparison between the investigated region and other areas around the world shows that both Q1i and Q1s for the Friuli region are among the lowest values ever measured, with the exception of the southern Apennines, which has the lowest measured Q1s. For case (ii), numerical simulation of the energy envelopes was performed using two-layered earth models, where the values of the intrinsic and scattering attenuation coefficients are both within 'reasonable ranges' when compared with the geological information. The theoretical envelopes calculated for the homogeneous model give a good fit to the synthetic envelopes calculated for the layered models; the best fit is obtained for scattering attenuation coefficients of the uniform model always greater than those of the layered model. The main result is consequently that scattering Q1s obtained using the MLTWA under the assumption of a uniform medium is overestimated, on average, by a factor 2. Finally, coda Q1 appears to be closer to the total Q1 than to the intrinsic Q1i, as predicted by the theory.
Sat, 01 Jan 2005 00:00:00 GMThttp://hdl.handle.net/2122/4092005-01-01T00:00:00Z
- Seismological constraints for the dyke emplacement of the July-August 2001 lateral eruption at Mt. Etna volcano, Italyhttp://hdl.handle.net/2122/5273Title: Seismological constraints for the dyke emplacement of the July-August 2001 lateral eruption at Mt. Etna volcano, Italy
Authors: Patanè, D.; Privitera, E.; Gresta, S.; Alparone, S.; Akinci, A.; Barberi, G.; Chiaraluce, L.; Cocina, O.; D'Amico, S.; De Gori, P.; Di Grazia, G.; Falsaperla, S.; Ferrari, F.; Gambino, S.; Giampiccolo, E.; Langer, H.; Maiolino, V.; Moretti, M.; Mostaccio, A.; Musumeci, C.; Piccinini, D.; Reitano, D.; Scarfì, L.; Spampinato, S.; Ursino, A.; Zuccarello, L.
Abstract: In this paper we report seismological evidence regarding the emplacement of the dike that fed the July 18 - August
9, 2001 lateral eruption at Mt. Etna volcano. The shallow intrusion and the opening of the eruptive fracture
system, which mostly occurred during July 12, and July 18, were accompanied by one of the most intense seismic
swarms of the last 20 years. A total of 2694 earthquakes (1 £ Md £ 3.9) were recorded from the beginning of the
swarm (July 12) to the end of the eruption (August 9). Seismicity shows the upward migration of the dike from
the basement to the relatively thin volcanic pile. A clear hypocentral migration was observed, well constraining
the upwards propagation of a near-vertical dike, oriented roughly N-S, and located a few kilometers south of the
summit region. Earthquake distribution and orientation of the P-axes from focal mechanisms indicate that the
swarm was caused by the local stress source related to the dike intrusion.
Fri, 01 Aug 2003 00:00:00 GMThttp://hdl.handle.net/2122/52732003-08-01T00:00:00Z
- High-Frequency Ground Motion in the Erzincan Region, Turkey:Inferences from Small Earthquakeshttp://hdl.handle.net/2122/2954Title: High-Frequency Ground Motion in the Erzincan Region, Turkey:Inferences from Small Earthquakes
Authors: Akinci, A.; Malagnini, L.; Hermann, R. B.; Pino, N. A.; Scognamiglio, L.; Eydogan, H.
Abstract: Distance scaling of earthquake-induced ground motion is studied in the
Erzincan region, located in the eastern part of the North Anatolian Fault zone. The
data set used in this study consists of 170 aftershocks of the MS ! 6.8 Erzincan
earthquake of 13 March 1992, with moment magnitudes between 1.5 and 4.0. In
order to empirically obtain the scaling relationships for the high-frequency S-wave
motion, regressions are carried out on 352 horizontal-component short-period seismograms,
all recorded within a hypocentral distance of 40 km, to empirically obtain
the scaling relationships for the high-frequency S-wave motion.
Peak ground velocities are measured in selected narrow-frequency bands, in the
frequency range of 1.0–16.0 Hz, and are subsequently regressed to define a piecewise
linear attenuation function, a set of excitation terms, and a set of site terms. Results
are modeled in the framework of random vibration theory, using a bilinear geometrical
spreading function, g(r), characterized by a crossover distance at 25 km:
g(r)!r"1.1 is used for r ! 25 km, whereas g(r)!r"0.5 is used for larger distances.
An extremely low-quality factor, Q(f ) ! 40(f /f ref)0.45, is used to describe the anelastic
crustal attenuation in the region, consistently with the independent results of
Akinci and Eyidogan (1996, 2000).
Excitation terms are well matched by using a Brune spectral model with stress
drop Dr ! 10 MPa (taken from the recent literature, Grosser et al., 1998). An
effective high-frequency, distance-independent rolloff spectral parameter, jeff !
0.02 sec, is obtained in this study. Peak ground acceleration predictions based on
these parameters show a much more rapid decrease with distance than the relations
usually used in Turkey, indicating that our results should only be applied to the
Erzincan region itself.
Sat, 01 Dec 2001 00:00:00 GMThttp://hdl.handle.net/2122/29542001-12-01T00:00:00Z
- Characteristics of the Ground Motion in Northeastern Italyhttp://hdl.handle.net/2122/2953Title: Characteristics of the Ground Motion in Northeastern Italy
Authors: Malagnini, L.; Akinci, A.; Hermann, R. B.; Pino, N. A.; Scognamiglio, L.
Abstract: A large data set of ground-velocity time histories from earthquakes that
occurred in Friuli-Venezia Giulia (northeastern Italy) was used to define regional
predictive relationships for ground motion, in the 0.25- to 14.0-Hz frequency band.
The bulk of the data set was provided by the seismic network run by Centro Ricerche
Sismologiche (CRS), a department of the Istituto Nazionale di Oceanografia e Geofisica
(OGS). A collection of 17,238 selected recordings from 1753 earthquakes was
compiled for the years 1995–1998, with magnitudes ranging from Mw !1 to 5.6.
Ninety-six three-component strong-motion waveforms belonging to the largest
events of the 1976–1977 Friuli seismic sequence were also taken from the ENEAENEL
accelerogram database and included in our data set. For the strongest event,
which occurred on 6 May 1976 at 20:00 local time, an average local magnitude ML
6.6 was computed by Bonamassa and Rovelli (1986). The inclusion of a large number
of acceleration time histories from this earthquake and six others, from magnitudes
from Mw 5.2 to magnitude Ms 6.1 (three of them of Ms !6.0), extends the validity
of the predictive relationships proposed in this study up to the highest magnitude
ever recorded in the region.
A total of 10,256 vertical-component and 6982 horizontal-component seismograms
were simultaneously regressed for excitation and site characteristics, as well
as for the crustal propagation, in the hypocentral distance range 20–200 km. Results
are given in terms of excitation, attenuation, and specific site for the vertical ground
motion, together with a horizontal-to-vertical ratio for each existing horizontalcomponent
seismometer. The regional propagation was modeled in the 0.5- to 14.0-
Hz frequency band by using a frequency-dependent piece wise continuous linear (in
a log–log space) geometrical spreading function and a frequency-dependent attenuation
parameter:
Q( f ) ! 260( f /1.0)0.55
The excitation spectra of larger events were modeled by using the regional propagation,
a single-corner frequency Brune spectral model characterized by an effective
stress parameter,
Dr ! 60 MPa,
and by a regional estimate of the near-surface, distance-independent, networkaveraged
attenuation parameter
j0 ! 0.045 sec
that was estimated from the rolloff of the empirical source spectra obtained from the
regressions. Other studies (De Natale et al., 1987; Cocco and Rovelli, 1989; Singh
et al., 2001) suggested large stress drops (Dr ! 30–100 MPa,) to explain the highfrequency
amplitude levels of the seismic radiation of the largest quakes of the 1976
sequence.
Predictions for peak ground acceleration (PGA) and pseudo–spectral velocity
(PSV) (5% damping) were computed through the use of the random vibration theory
(RVT), with the parameters obtained from the regressions of this study.
Thu, 01 Aug 2002 00:00:00 GMThttp://hdl.handle.net/2122/29532002-08-01T00:00:00Z
- Evaluation of Deep Sediment Velocity Structure in the New Madridhttp://hdl.handle.net/2122/3747Title: Evaluation of Deep Sediment Velocity Structure in the New Madrid
Authors: Julia, J.; Herrmann, R. B.; Ammon, C.; Akinci, A.
Abstract: Detailed knowledge of the physical properties of the sediments filling
the Mississippi Embayment has proven critical to both unravel the tectonic framework
operating in the region and assess the seismic hazards posed by the New Madrid
Seismic Zone. In this article we show that independent geotechnical estimates for Pand
S-wave velocities are compatible with a sedimentary model of K-feldspar clasts
embeded in water, and we test its validity by modeling receiver functions at a number
of broadband stations. By constraining the bulk sediment thicknesses beneath each
station from independent reflection profiling estimates, we have been able to recover
the depth to the top of the Cretaceous from the receiver function data at individual
stations. Our receiver function modeling thus provides confidence in the velocity and
density structures extrapolated from in situ geotechnical measurements in the Upper
Mississippi Embayment.
Thu, 01 Jan 2004 00:00:00 GMThttp://hdl.handle.net/2122/37472004-01-01T00:00:00Z
- Attenuative Dispersion of P Waves and Crustal Qhttp://hdl.handle.net/2122/3752Title: Attenuative Dispersion of P Waves and Crustal Q
Authors: Akinci, A.; Mejia, J.; Jemberie, A.
Abstract: Abstract—We have measured group delays of the spectral components of high-frequency P-waves
along two portions of the North Anatolian Fault Zone (NAFZ) in Turkey and in a region of southern
Germany. Assuming that the observed dispersion is associated with attenuation in the crust and that it can
be described by a continuous relaxation model, we obtained Q and the high-frequency relaxation times for
those waves for each of the three regions. Individual P-wave Q values exhibit large scatter, but mean values
in the NAFZ increase from about 25 to 60 over the distance range 5–90 km. Mean Q values are somewhat
higher in the eastern portion of the NAFZ than in the western portion for measurements made at distances
between 10 and 30 km. P-wave Q values in Germany range between about 50 and 300 over the hypocentral
distance range 20–130 km. In that region we separated the effects of Q for basement rock (2–10 km depth)
from that of the overlying sediment (0–2 km depth) using a least-squares method. Q varies between 100
and 500 in the upper 8–10 km of basement, with mean values for most of the distance range being about
250. Q in the overlying sediments ranges between 6 and 10. Because of large scatter in the Q determinations
we investigated possible effects that variations of the source-time function of the earthquakes and
truncation of the waveform may have on Q determinations. All of our studies indicate that measurement
errors are relatively large and suggest that useful application of the method requires many observations,
and that the method will be most useful in regions where the number of oscillations following the initial P
pulse is minimized. Even though there is large scatter in our Q determinations, the mean values that we
obtained in Turkey are consistent with those found in earlier studies. Our conclusions that Q is significantly
higher in the basement rock of Germany than in the basement rock of Turkey and that Q is lower in
western Turkey than in eastern Turkey are also consistent with results of Q studies using Lg coda.
Thu, 01 Jan 2004 00:00:00 GMThttp://hdl.handle.net/2122/37522004-01-01T00:00:00Z
- The 2009 Abruzzo Earthquake, Italyhttp://hdl.handle.net/2122/6702Title: The 2009 Abruzzo Earthquake, Italy
Authors: Akinci, A.; Malagnini, L.
Abstract: The Abruzzo earthquake on April 6
this year was surprising for several reasons.
Although the historical record shows that the
city of L’Aquila has suffered intensity IX or
higher several times, this earthquake caused
stronger shaking than any other in the area
for the past 300 years. In addition, the
mechanism displays clear extensional stresses
in a region characterized by shortening
during the Miocene and the mainshock was
heralded by a foreshock swarm.
Thu, 01 Jan 2009 00:00:00 GMThttp://hdl.handle.net/2122/67022009-01-01T00:00:00Z
- M ≥ 7 earthquake rupture forecast and time-dependent probability for the sea of Marmara region, Turkeyhttp://hdl.handle.net/2122/10708Title: M ≥ 7 earthquake rupture forecast and time-dependent probability for the sea of Marmara region, Turkey
Authors: Murru, Maura; Akinci, Aybige; Falcone, Giuseppe; Pucci, Stefano; Console, Rodolfo; Parsons, T.
Abstract: We forecast time-independent and time-dependent earthquake ruptures in the Marmara region of Turkey for the next 30 years using a new fault segmentation model. We also augment time-dependent Brownian passage time (BPT) probability with static Coulomb stress changes (ΔCFF) from interacting faults. We calculate Mw > 6.5 probability from 26 individual fault sources in the Marmara region. We also consider a multisegment rupture model that allows higher-magnitude ruptures over some segments of the northern branch of the North Anatolian Fault Zone beneath the Marmara Sea. A total of 10 different Mw = 7.0 to Mw = 8.0 multisegment ruptures are combined with the other regional faults at rates that balance the overall moment accumulation. We use Gaussian random distributions to treat parameter uncertainties (e.g., aperiodicity, maximum expected magnitude, slip rate, and consequently mean recurrence time) of the statistical distributions associated with each fault source. We then estimate uncertainties of the 30 year probability values for the next characteristic event obtained from three different models (Poisson, BPT, and BPT + ΔCFF) using a Monte Carlo procedure. The Gerede fault segment located at the eastern end of the Marmara region shows the highest 30 year probability, with a Poisson value of 29% and a time-dependent interaction probability of 48%. We find an aggregated 30 year Poisson probability of M > 7.3 earthquakes at Istanbul of 35%, which increases to 47% if time dependence and stress transfer are considered. We calculate a twofold probability gain (ratio time dependent to time independent) on the southern strands of the North Anatolian Fault Zone.
Fri, 01 Apr 2016 00:00:00 GMThttp://hdl.handle.net/2122/107082016-04-01T00:00:00Z
- Implementing the Effect of the Rupture Directivity on PSHA for the City of Istanbul, Turkeyhttp://hdl.handle.net/2122/10774Title: Implementing the Effect of the Rupture Directivity on PSHA for the City of Istanbul, Turkey
Authors: Spagnuolo, Elena; Akinci, Aybige; Herrero, André; Pucci, Stefano
Abstract: In the present study, we improve the probabilistic seismic-hazard assessment (PSHA), taking into account fault rupture-related parameters that sensibly affect the azimuthal variability of the ground motion. The study area is the Marmara region (Turkey), characterized by one of the highest levels of seismic risk in Europe and the Mediterranean region. The seismic hazard in the city of Istanbul is mainly associated with two active fault segments having well-defined geometry, focal mechanism, and rate of activity. Deterministic dynamic models are also available in this area (Aochi and Ulrich, 2015) that aimed at evaluating the seismic potential of the Marmara region. These models provide the statistical distribution for the hypocenter position, which is particularly relevant for rupture directivity. The aim of this work is to incorporate all the available information about the seismic potential of the Marmara region in a PSHA framework. We use an analytical model for directivity (Spudich and Chiou, 2008; Spudich et al., 2013) to integrate rupture-related parameters inside the PSHA standard procedure. Because the directivity effect is conditional on the hypocenter position, which is not a priori known, we assume at first ad hoc Gaussian distributions centered in the western, eastern, or middle part of the two fault segments. Our results show that the correction for directivity introduces a significant contribution (up to 25% of relative increase at 2 s) to the hazard maps computed with the standard PSHA practice (given in terms of pseudospectral accelerations having 10% probability of exceedance in 50 years). The hazard maps sensibly change when we use the distribution for the hypocenter position informed by the statistical treatment of dynamic simulations. Thus, integrating new variables in the PSHA in combination with properly informed probability density functions is not only feasible, but also recommended for a comprehensive PSHA.
Fri, 01 Jan 2016 00:00:00 GMThttp://hdl.handle.net/2122/107742016-01-01T00:00:00Z
- A Regional Ground Motion Excitation attenuation Model for the San Francisco Regionhttp://hdl.handle.net/2122/2306Title: A Regional Ground Motion Excitation attenuation Model for the San Francisco Region
Authors: Malagnini, L.; Mayeda, K.; Uhrhammer, R.; Akinci, A.; Herrmann, R. B.
Abstract: By using small-to-moderate-sized earthquakes located within ~200 km of San
Francisco, we characterize the scaling of the ground motions for frequencies ranging
between 0.25 and 20 Hz, obtaining results for geometric spreading, Q(f), and site
parameters using the methods of Mayeda et al. (2005) and Malagnini et al. (2004). The
results of the analysis show that, throughout the Bay Area, the average regional
attenuation of the ground motion can be modeled with a bilinear geometric spreading
function with a 30 km crossover distance, coupled to an anelastic function
!
exp "
#fr
$Q( f )
%
&
'
(
)
* ,
where: Q(f)=180 f 0.42. A body-wave geometric spreading, g(r)= r -1.0, is used at short
hypocentral distances (r < 30 km), whereas g(r)= r -0.6 fits the attenuation of the spectral
amplitudes at hypocentral distances beyond the crossover.
The frequency-dependent site effects at 12 of the Berkeley Digital Seismic
Network (BDSN) stations were evaluated in an absolute sense using coda-derived source
spectra.
Our results show: i) the absolute site response for frequencies ranging between 0.3 Hz
and 2.0 Hz correlate with independent estimates of the local magnitude residuals (dML)
for each of the stations; ii) moment-magnitudes (MW) derived from our path and sitecorrected
spectra are in excellent agreement with those independently derived using fullwaveform
modeling as well as coda-derived source spectra; iii) we use our weak-motionbased
relationships to predict motions region wide for the Loma Prieta earthquake, well
above the maximum magnitude spanned by our data set, on a completely different set of
stations. Results compare well with measurements taken at specific NEHRP site classes;
iv) an empirical, magnitude-dependent scaling was necessary for the Brune stress
parameter in order to match the large magnitude spectral accelerations and peak ground
velocities with our weak-motion-based model.
Sun, 01 Jan 2006 00:00:00 GMThttp://hdl.handle.net/2122/23062006-01-01T00:00:00Z
- Physics‐Based Broadband Ground‐Motion Simulations for ProbableMw≥7.0 Earthquakes in the Marmara Sea Region (Turkey)http://hdl.handle.net/2122/10772Title: Physics‐Based Broadband Ground‐Motion Simulations for ProbableMw≥7.0 Earthquakes in the Marmara Sea Region (Turkey)
Authors: Akinci, Aybige; Aochi, Hideo; Herrero, André; Pischiutta, Marta; Karanikas, Dimitri
Abstract: The city of Istanbul is characterized by one of the highest levels of seismic risk in the Mediterranean region. An important source of such increased risk is the high probability of large earthquake occurrence during the coming years, which stands at about 65% likelihood owing to the existing seismic gap and the post-1999 earthquake stress transfer at the western portion of the North Anatolian fault zone. In this study, we simulated hybrid broadband time histories from selected earthquakes having magnitude Mw >7:0 in the Sea of Marmara within 10–20 km of Istanbul, the most probable scenarios for simulated generation of the devastating 1509 event in this region. Physics-based rupture scenarios, which may be an indication of potential future events, are adopted to estimate the ground-motion characteristics and its variability in the region. Two simulation techniques are used to compute a realistic time series, considering generic rock site conditions. The first is a full 3D wave propagation method used for generating low-frequency seismograms, and the second is a stochastic finite-fault model approach based on dynamic corner-frequency high-frequency seismograms. Dynamic rupture is generated and computed using a boundary integral equation method, and the propagation in the medium is realized through a finite-difference approach. The results from the two simulation techniques are then merged by performing a weighted summation at intermediate frequencies to calculate a broadband synthetic time series. The simulated hybrid broadband ground motions are validated by comparing peak ground acceleration, peak ground velocity (PGV), and spectral accelerations (5% damping) at different periods with the ground-motion prediction equations in the region. Our simulations reveal strong rupture directivity and supershear rupture effects over a large spatial extent, which generate extremely high near-fault motions exceeding the 250 cm=s PGV along the entire length of the ruptured fault.
Sun, 01 Jan 2017 00:00:00 GMThttp://hdl.handle.net/2122/107722017-01-01T00:00:00Z
- Loss estimation in Istanbul based on deterministic earthquake scenarios of the Marmara Sea region (Turkey)http://hdl.handle.net/2122/5600Title: Loss estimation in Istanbul based on deterministic earthquake scenarios of the Marmara Sea region (Turkey)
Authors: Ansal, A.; Akinci, A.; Cultrera, G.; Erdik, M.; Pessina, V.; Tönük, G.; Ameri, G.
Abstract: The rapid urban development in Istanbul has lead to an increase in the exposure levels of the urban vulnerability. Due to the steadily increasing population, with improper land-use planning, inappropriate construction techniques and inadequate infrastructure systems, associated with an existing high hazard level, Istanbul is one of the most risky cities in the Mediterranean region. Estimations of casualties and losses, expected for given earthquake scenarios, are necessary to develop sustainable rehabilitation programs and for improving preparedness. Deterministic hazard scenarios and time-dependent probabilistic hazard assessment were used as input to a GIS-based loss estimation model, to evaluate the earthquake risk for Istanbul.
The deterministic ground shaking scenarios, used for loss estimation in Istanbul, were defined in terms of acceleration and velocity time series for recognized reference earthquakes caused by different rupture models along extended sources. The ground motions were calculated for the whole metropolitan area extending over a grid system of 25×100 km2.
For the case of Istanbul, the representative scenario was selected by comparing the simulated peak values and response spectra with the empirical ground motion models available for the area. Simulated values are within one standard deviation of the empirical regressions.
The availability of wide-ranging building inventory data allowed the application of a GIS-based loss estimation model (KoeriLoss-V2) to evaluate different loss scenarios depending on the ground shaking input, as well as to consider the implications of mitigation actions. It was found that 30% of the buildings in the metropolitan area may be in need of either strengthening or demolition to achieve an adequate degree of life safety.
Wed, 01 Apr 2009 00:00:00 GMThttp://hdl.handle.net/2122/56002009-04-01T00:00:00Z
- Weak-motion-based attenuation relationships for Israelhttp://hdl.handle.net/2122/4219Title: Weak-motion-based attenuation relationships for Israel
Authors: Meirova, T.; Hofstetter, A.; Ben-Avraham, Z.; Steinberg, D.; Malagnini, L.; Akinci, A.
Abstract: We performed a regional study of earthquake ground motion scaling relations to provide the
seismic hazard community of Israel with a new attenuation relationship that could be used for
the prediction of earthquake-induced ground motion. Strong earthquakes are rather scarce in
Israel and the existing collection of records from strong earthquakes is not sufficient to allowthe
use of traditional regression methods to develop a regional attenuation relationship. We used
velocity seismograms from the Israel Seismic Network to estimate the distance and frequency
dependence of ground motion in the Israel region from frequent, smaller regional earthquakes.
Our analyses included 4814 waveforms recorded by 30 stations of the Israel Seismic Network
from 2000 to 2005. We restricted our analysis to 330 events recorded at five or more stations,
with duration magnitudes ranging between 1.0 and 5.2. We derived empirical excitation,
site and regional attenuation terms by regressing the peak amplitudes of narrowband-filtered
seismograms around the shear wave arrivals and the rms Fourier spectral amplitudes taken
around the specific sampling frequency. In order to optimize the attenuation parameters in our
scaling model, we used a simple grid search. An optimal solution for minimal error between
empirical and theoretical attenuation function was found for the quality parameter Q( f ) = 298 f^0.67 and the geometrical spreading g(r ) parametrized as a bilinear, piecewise function:
r^−0.74 for r ≤ 60 km and r^−0.47 for r > 60 km. The spectral parameters κ of 0.015 s and stress
drop increasing from 0.3 to 4 MPa were used to model the excitation spectra.
A theoretical modelling effort based on Brune’s source spectrum and Random Vibration
Theory (RVT) was performed on the attenuation and source parameters estimated in this study.
Comparison of the attenuation relationship derived with locally measured ground motions
shows excellent agreement with the data in the magnitude range forwhichwe have observations
and seems to be adequate for predictions of earthquake ground motion for the Israel region.
Comparison of Peak Ground Acceleration (PGA) predictions, based on our scaling relationship
with those that have been recently used for seismic hazard analysis in Israel shows that our
attenuation relationship predicts significantly lower ground motions than other relations.
Tue, 01 Jan 2008 00:00:00 GMThttp://hdl.handle.net/2122/42192008-01-01T00:00:00Z
- Progetto S2 Valutazione del potenziale sismogenetico e probabilità dei forti terremoti in Italiahttp://hdl.handle.net/2122/3767Title: Progetto S2 Valutazione del potenziale sismogenetico e probabilità dei forti terremoti in Italia
Authors: Akinci, A.
Sat, 01 Dec 2007 00:00:00 GMThttp://hdl.handle.net/2122/37672007-12-01T00:00:00Z
- Earthquake Disaster Scenario Prediction and Loss Modelling for Urban Areashttp://hdl.handle.net/2122/3421Title: Earthquake Disaster Scenario Prediction and Loss Modelling for Urban Areas
Authors: Spence, R.; So, E.; Ameri, G.; Akinci, A.; Cocco, M.; Cultrera, G.; Franceschina, G.; Pacor, F.; Pessina, V.; Lombardi, A. M.; Zonno, G.; Carvalho, A.; Campos Costa, A.; Coelho, E.; Pitilakis, K.; Anastasiadis, A.; Kakderi, K.; Alexoudi, M.; Ansal, A.; Erdic, M.; Tonuk, G.; Demircioglu, M.
Abstract: The overall aim of Sub-Project 10 (Earthquake disaster scenario predictions and loss modelling for urban areas) has been to create a tool, based on state-of-the-art loss modelling software, to provide strong, quantified statements about the benefits of a range of possible mitigation actions, in order to support decision-making by urban authorities for seismic risk mitigation strategies. A further larger aim has been to contribute to a seismic risk mitigation policy for future implementation at European level. Among the European cities for which loss estimation studies have been carried out are Istanbul, Lisbon and Thessaloniki, and tools, using GIS mapping, have been developed by research teams in each of these cities; these were made available for further development to examine mitigation strategies within SP10. Related research studies – on ground motion estimation, on the assessment of human casualties, and on the evaluation of uncertainty have been carried out by other research teams across Europe which includes INGV, UCAM and USUR respectively. In all three of the cities, a common general approach to loss modelling has been adopted which includes representing the earthquake hazard as a set of alternative ground motion scenarios (typically those with an expected recurrence periods of 50 and 500 years), and applying the ground motion over a target area of known population and building stock. Losses have then been estimated for this target area in terms of levels of building damage and human casualties expected both in the existing state of the target area, and after certain selected potential mitigation actions have been carried out. This has been done in each case using building stock classifications and vulnerability data specific to the particular city concerned. In each case the scope of the proposed mitigation action has been described, and its expected benefit in terms of reduced losses and human casualties has been determined with some preliminary assessment of uncertainty.
Sun, 01 Jul 2007 00:00:00 GMThttp://hdl.handle.net/2122/34212007-07-01T00:00:00Z
- Investigating the effectiveness of rup- ture directivity during the August 24, 2016 Mw 6.0 central Italy earthquakehttp://hdl.handle.net/2122/10860Title: Investigating the effectiveness of rup- ture directivity during the August 24, 2016 Mw 6.0 central Italy earthquake
Authors: Spagnuolo, Elena; Cirella, Antonella; Akinci, Aybige
Abstract: In this study we investigate directivity effects associated to the August 24, 2016 Mw 6, central Italy earth- quake taking into account the source rupture heterogeneities. We use the directivity predictor proposed by Spudich et al. (2004) which is derived from the isochrones theory. The directivity is computed using a source to site geometry and a focal mechanism. For its simplicity it can be computed once that a moment tensor solution is available. We use this technique to validate the real time solutions. Moreover, because the directivity predictor depends on the rupture velocity it can be used as a proxy to validate the possible rupture history. For the aforementioned reasons our method revealed fruitful for real time applications and helpful to constrain a few main rupture features for further analysis.
Fri, 01 Jan 2016 00:00:00 GMThttp://hdl.handle.net/2122/108602016-01-01T00:00:00Z
- Effect of time-dependence on probabilistic seismic hazard maps and deaggregation for the central apennines, Italyhttp://hdl.handle.net/2122/4230Title: Effect of time-dependence on probabilistic seismic hazard maps and deaggregation for the central apennines, Italy
Authors: Akinci, A.; Galadini, F.; Pantosti, D.; Petersen, M.; Malagnini, L.; Perkins, D.
Abstract: We produce probabilistic seismic hazard assessments for the Central Apennines, Italy, using time-dependent models that are characterized using a Brownian Passage Time (BPT) recurrence model. Using aperiodicity parameters, of 0.3, 0.5, and 0.7, we examine the sensitivity of the probabilistic ground motion and its deaggregation to these parameters. For the seismic source model we incorporate both smoothed historical seismicity over the area and geological information on faults. We use the maximum magnitude model for the fault sources together with a uniform probability of rupture along the fault (floating fault model) to model fictitious faults to account for earthquakes that cannot be correlated with known geologic structural segmentation.
We show maps for peak ground acceleration (PGA) and 1.0-Hz spectral acceleration (SA1) on rock having 10% probability of exceedence (PE) in 50 years. We produce maps to compare the separate contributions of smoothed seismicity and fault components. In addition we construct maps that show sensitivity of the hazard for different parameters and the Poisson model.
For the Poisson model, the addition of fault sources to the smoothed seismicity raises the hazard by 50 % at locations where the smoothed seismicity contributes the highest hazard, and up to 100 % at locations where the hazard from smoothed seismicity is low. For the strongest aperiodicity parameter (smallest ), the hazard may further increase 60-80 % or more or may decrease by as much as 20 %, depending on the recency of the last event on the fault that dominates the hazard at a given site.
In order to present the most likely earthquake magnitude and/or the most likely source-site distance for scenario studies, we deaggregate the seismic hazard for SA1 and PGA for two important cities (Roma and l’Aquila) . For PGA, both locations show the predominance of local sources, having magnitudes of about 5.3 and 6.5 respectively. For SA1 at a site in Rome, there is significant contribution from local smoothed seismicity, and an additional contribution from the more distant Apennine faults having magnitude around 6.8. For l’Aquila, the predominant sources remain local.
In order to show the variety of impact of different values we also obtained deaggregations for another three sites. In general, as decreases (periodicity increases), the deaggregation indicates that the hazard is highest near faults with the highest earthquakes rates. This effect is strongest for the long-period (1 s) ground motions.
Tue, 01 Jan 2008 00:00:00 GMThttp://hdl.handle.net/2122/42302008-01-01T00:00:00Z
- Estimating Absolute Site Effectshttp://hdl.handle.net/2122/3753Title: Estimating Absolute Site Effects
Authors: Malagnini, L.; Mayeda, K.; Akinci, A.; Bragato, P. L.
Abstract: We use previously determined direct-wave attenuation functions as well
as stable, coda-derived source excitation spectra to isolate the absolute S-wave site
effect for the horizontal and vertical components of weak ground motion. We use
selected stations in the seismic network of the eastern Alps.
A detailed regional attenuation function derived by Malagnini et al. (2002) for the
region is used to correct the vertical and horizontal S-wave spectra. These corrections
account for the gross path effects (i.e., all distance-dependent effects), although the
source and site effects are still present in the distance-corrected spectra. The main
goal of this study is to isolate the absolute site effect (as a function of frequency) by
removing the source spectrum (moment-rate spectrum) from the distance-corrected
S-wave spectra. Typically, removing the S-wave source spectrum is difficult because
of inadequate corrections for the source radiation pattern, directivity, and random
interference. In addition to complexities near the source, 2D and 3D structure beneath
the recording site will result in an azimuth-dependent site effect. Since the direct
wave only samples a narrow range in takeoff and backazimuth angles, multistation
averaging is needed to minimize the inherent scatter.
Because of these complicating effects, we apply the coda methodology outlined
by Mayeda et al. (2003) to obtain stable moment-rate spectra. This methodology
provides source amplitude and derived source spectra that are a factor of 3–4 times
more stable than those derived from direct waves. Since the coda is commonly
thought of as scattered energy that samples all ray parameters and backazimuths, it
is not very sensitive to the source radiation pattern and 3D structure. This property
makes it an excellent choice for use in obtaining average parameters to describe the
source, site, and path effects in a region. Due to the characteristics of the techniques
used in this study, all the inverted quantities are azimuthally averaged, since the
azimuthal information is lost in the processing.
Our results show that (1) all rock sites exhibited deamplification phenomena due
to absorption at frequencies ranging between 0.5 and 12 Hz (the available bandwidth),
on both the horizontal and vertical components; (2) rock-site transfer functions
showed large variability at high-frequency; (3) vertical-motion site transfer
functions show strong frequency dependence; (4) horizontal-to-vertical (H/V) spectral
ratios do not reproduce the charactersitics of the true horizontal site transfer
functions; and (5) traditional, relative site terms obtained by using reference rock
sites can be misleading in inferring the behaviors of true site transfer functions, since
most rock sites have nonflat responses due to shallow heterogeneities resulting from
varying degrees of weathering.
Our stable source spectra are used to estimate the total radiated seismic energy
and to compare against similar results obtained for different regions of the world.
We find that the earthquakes in this region exhibit nonconstant dynamic stress drop
scaling, which gives further support for a fundamental difference in rupture dynamics
between small and large earthquakes.
Thu, 01 Jan 2004 00:00:00 GMThttp://hdl.handle.net/2122/37532004-01-01T00:00:00Z
- Nucleation speed limit on remote fluid-induced earthquakeshttp://hdl.handle.net/2122/10773Title: Nucleation speed limit on remote fluid-induced earthquakes
Authors: Parsons, Tom; Malagnini, Luca; Akinci, Aybige
Abstract: Earthquakes triggered by other remote seismic events are explained as a response to long-traveling seismic waves that temporarily stress the crust. However, delays of hours or days after seismic waves pass through are reported by several studies, which are difficult to reconcile with the transient stresses imparted by seismic waves. We show that these delays are proportional to magnitude and that nucleation times are best fit to a fluid diffusion process if the governing rupture process involves unlocking a magnitude-dependent critical nucleation zone. It is well established that distant earthquakes can strongly affect the pressure and distribution of crustal pore fluids. Earth's crust contains hydraulically isolated, pressurized compartments in which fluids are contained within low-permeability walls. We know that strong shaking induced by seismic waves from large earthquakes can change the permeability of rocks. Thus, the boundary of a pressurized compartment may see its permeability rise. Previously confined, overpressurized pore fluids may then diffuse away, infiltrate faults, decrease their strength, and induce earthquakes. Magnitude-dependent delays and critical nucleation zone conclusions can also be applied to human-induced earthquakes.
Tue, 01 Aug 2017 00:00:00 GMThttp://hdl.handle.net/2122/107732017-08-01T00:00:00Z
- Ground-Motion Scaling in Eastern Sicily, Italyhttp://hdl.handle.net/2122/2952Title: Ground-Motion Scaling in Eastern Sicily, Italy
Authors: Scognamiglio, L.; Malagnini, L.; Akinci, A.
Abstract: We describe the characteristics of crustal wave propagation in eastern
Sicily by using the background seismicity of the area. We follow the approach described
by Malagnini, Hermann, and Di Bona (2000) and Malagnini et al. (2002).
Our data set consists of 106 earthquakes recorded by nine three-component digital
seismic stations between 1994 and 2001. We used only crustal events (depths shallower
than 25 km), with local magnitudes ranging from 1.0 to 4.3, and hypocentral
distances from 10 to 130 km.
Peak ground velocities from 1311 narrow bandpass-filtered waveforms are measured
in the frequency range 1.0–16.0 Hz, and regressed to define crustal propagation,
excitation, and site characteristics, with respect to a reference station. A subsequent
modeling effort is carried out, through the use of random vibration theory (RVT), for
obtaining a quantitative evaluation of the apparent geometrical spreading g(r), and
of the crustal quality factor Q( f ). An attenuation parameter, j0, is also evaluated
relative to a reference rock site.
The attenuation and source parameters estimated in this study are used through
the RVT in order to predict the peak horizontal ground acceleration (PGA), and the
5% damping pseudoacceleration spectra (PSA).
Fri, 01 Apr 2005 00:00:00 GMThttp://hdl.handle.net/2122/29522005-04-01T00:00:00Z
- Hibrid broadband Ground-Motion Simulations for the 2016 Amatrice Earthquake, Central Italy, and Sensitivity of Ground-Motion to Earthquake Source Parametershttp://hdl.handle.net/2122/12402Title: Hibrid broadband Ground-Motion Simulations for the 2016 Amatrice Earthquake, Central Italy, and Sensitivity of Ground-Motion to Earthquake Source Parameters
Authors: Pischiutta, Marta; Akinci, Aybige; Tinti, Elisa; Cirella, Antonella; Herrero, André
Abstract: On 24th August 2016 at 01:36 UTC a MW 6.0 earthquake struck several villages in central Italy, among which Accumoli, Amatrice and Arquata del Tronto. It caused 299 fatalities, major destruction and extensive damage in the surrounding area (up to 11 intensity degree). The earthquake was recorded by 350 digital accelerometers be- longing to the National Accelerometric Network (RAN) of the Italian Department of Civil Protection, to the National Seismic Network (Rete Sismica Nazionale, RSN) of the Istituto Nazionale di Geofisica e Vulcanologia (INGV), and to other local net- works. This earthquake ruptured a NW–SE oriented normal fault, according the prevailing extensional tectonics of the area.The maximum accelera- tion was observed at Amatrice station (AMT) with epicentral distance of 15 km, reaching 916 cm/s2 and 445.6 cm/s2 on E-W and N-S components, respectively. Motivated by the high levels of observed ground motion and damage, we have computed synthetics broadband time series for engineering purposes. To produce high-frequency seismograms, we have used a stochastic finite-fault model approach based on dynamic corner-frequency.
Sat, 01 Sep 2018 00:00:00 GMThttp://hdl.handle.net/2122/124022018-09-01T00:00:00Z
- Comparison of ground motion hybrid simulations to NGA modified GMPE in the Marmara Sea region (Turkey) in a directivity rupture context.http://hdl.handle.net/2122/12403Title: Comparison of ground motion hybrid simulations to NGA modified GMPE in the Marmara Sea region (Turkey) in a directivity rupture context.
Authors: Pischiutta, Marta; Akinci, Aybige; Taroni, Matteo; Spagnuolo, Elena; Herrero, André; Aochi, Hideo
Abstract: We have simulated strong ground motions for two Mw>7.0 rupture scenarios on the North Anatolian Fault, in the Marmara Sea within 10-20 km of Istanbul. This city is characterized by one of the highest levels of seismic risk in Europe and the Mediterranean region. The increased risk in Istanbul is due to the high probability of the occurrence of a large earthquake, which stands at about 65% during the coming years. To estimate the ground motion characteristics and its variability in the region we have adopted physics-based rupture scenarios, simulating hybrid broadband time histories. We have merged two simulation techniques: a full 3D wave propagation method to generate low-frequency seismograms (Aochi and Ulrich, 2015) and the stochastic finite-fault model approach based on a dynamic corner frequency (Motazedian and Atkinson, 2005) to simulate high-frequency seismograms. They are merged to compute realistic broad band hybrid time series.
The comparison of intensity measures (PGA, PGV, SA) on our simulations with recently proposed Ground Motion Prediction Equations (GMPEs) in the region (Boore & Atkinson, 2008; Chiou & Young, 2008; Akkar & Bommer, 2010; Akkar & Cagnan, 2010) points out the rupture directivity and super-shear rupture effects associated to these cases. In order to improve the comparison, we use the GMPE proposed by Boore & Atkinson (2008) with the directivity correction proposed by Spudich & Chiu (2008). This study highlights the importance of the directivity of the rupture for the hazard estimation in the region of the Marmara Sea and especially for the city of Istanbul.
Thu, 01 Dec 2016 00:00:00 GMThttp://hdl.handle.net/2122/124032016-12-01T00:00:00Z
- Unbiased Moment Rate Spectra and Absolute Site Effects in the Kachchh Basin, India, from the Analysis of the Aftershocks of the 2001 Mw7.6 Bhuj Earthquakehttp://hdl.handle.net/2122/2472Title: Unbiased Moment Rate Spectra and Absolute Site Effects in the Kachchh Basin, India, from the Analysis of the Aftershocks of the 2001 Mw7.6 Bhuj Earthquake
Authors: Malagnini, L.; Bodin, P.; Mayeda, K.; Akinci, A.
Abstract: What can be learned about absolute site effects on ground motions, with
no geotechnical information available, in a very poorly instrumented region? In addition,
can reliable source spectra be computed at a temporary deployment? These
challenges motivated our current study of aftershocks of the 2001 Mw 7.6 Bhuj
earthquake, in western India, where we decouple the ambiguity between absolute
source radiation and site effects by first computing robust estimates of coda-derived
moment-rate spectra of about 200 aftershocks in each of two depth ranges. Crustal
attenuation and spreading relationships, based on the same data used here, were
determined in an an earlier study.
Using our new estimates of source spectra, and our understanding of regional wave
propagation, for direct S waves we isolate the absolute site terms for the stations of
the temporary deployment. Absolute site terms for each station were determined in
an average sense for the three components of the ground motion via an L1-norm
minimization. Results for each site were averaged over wide ranges of azimuths and
incidence angles.
The Bhuj deployment is characterized by a variable shallow geology, mostly of
soft sedimentary units. Vertical site terms in the region were observed to be almost
featureless (i.e., flat), with amplifications slightly 1.0 within wide frequency ranges.
As a result, the horizontal-to-vertical (H/V) spectral ratios observed at the deployment
mimic the behavior of the corresponding absolute horizontal site terms, and
they generally overpredict them. This differs significantly from results for sedimentary
rock sites (limestone, dolomite) obtained by Malagnini et al. (2004) in northeastern
Italy, where the H/V spectral ratios had little in common with the absolute
horizontal site terms.
Spectral ratios between the vector sum of the computed horizontal site terms for
the temporary deployment with respect to the same quantity computed at the hardest
rock station available, BAC1, are seriously biased by its nonflat, nonunitary site
response. This indicates that, occasionally, the actual behavior of a rock outcrop may
be far from that of an ideal, reference site (Steidl et al., 1996).
Sun, 01 Jan 2006 00:00:00 GMThttp://hdl.handle.net/2122/24722006-01-01T00:00:00Z
- Ensemble Smoothed Seismicity Models for the New Italian Probabilistic Seismic Hazard Maphttp://hdl.handle.net/2122/12296Title: Ensemble Smoothed Seismicity Models for the New Italian Probabilistic Seismic Hazard Map
Authors: Akinci, Aybige; Moschetti, Morgan; Taroni, Matteo
Abstract: We develop a long-term (a few decades or longer) earthquake rate forecast for Italy based on smoothed seismicity for incor- poration in the 2017–2018 Italian Probabilistic Seismic Haz- ard Maps (IPSHM). Because the earthquake rate models from previous IPSHM were computed using source zones that were drawn around seismicity and tectonic provinces, the present model will be the first introduction of the smoothed seismic- ity method into the IPSHM. Smoothed seismicity models are constructed from both historical CPTI15 (Catalogo Parame- trico dei Terremoti Italiani, 1000–2014) and instrumental (1981–2016) earthquake catalogs and use both fixed and adaptive smoothing methods. We compute spatial likelihood values comparing the spatial distribution of observed earth- quakes with a suite of trial earthquake rate models to optimize smoothing parameters and catalogs. Then we produce an en- semble model using two different smoothing models (adap- tive and fixed) and two earthquake catalogs (historical and instrumental), which are weighted equally through a logic- tree approach to improve the forecast capability. We also compare our optimized smoothed seismicity models with the best two models of the Italian Collaboratory for the Study of Earthquake Predictability (CSEP) experiment and retro- spectively test them with the CSEP methodology. We ob- served that the ensemble model performs slightly better than the optimized fixed and the adaptive smoothing seismic- ity models obtained in this study and the best time-indepen- dent model of the CSEP Italian experiment. The preferred ensemble model forecasts an annual rate of 1.47 M ≥ 5:0 earthquakes, with higher rates mainly concentrating along the Apennines chain, eastern Alps, Calabria, and northeast Sicily. Finally, six ensemble models are created from the differ- ent smoothing methods using different weights through a logic-tree approach to estimate the uncertainty associated with the model.
Fri, 01 Jun 2018 00:00:00 GMThttp://hdl.handle.net/2122/122962018-06-01T00:00:00Z
- High-frequency ground-motion parameters from weak-motion data in the Sicily Channel and surrounding regionshttp://hdl.handle.net/2122/12297Title: High-frequency ground-motion parameters from weak-motion data in the Sicily Channel and surrounding regions
Authors: D'Amico, Sebastiano; Akinci, Aybige; Pischiutta, Marta
Abstract: In this paper we characterize the high-frequency (1.0–10 Hz) seismic wave crustal attenuation and the source excitation in the Sicily Channel and surrounding regions using background seismicity from weak-motion database. The data set includes 15 995 waveforms related to earthquakes having local magnitude ranging from 2.0 to 4.5 recorded between 2006 and 2012. The observed and predicted ground motions form the weak-motion data are evaluated in several narrow frequency bands from 0.25 to 20.0 Hz. The filtered observed peaks are regressed to specify a proper functional form for the regional attenuation, excitation and site specific term separately. The results are then used to calibrate effective theoretical attenuation and source excitation models using the random vibration theory. In the log–log domain, the regional seismic wave attenuation and the geometrical spreading coefficient are modelled together. The geometrical spreading coefficient, g(r), modelled with a bilinear piecewise functional form and given as g(r) ∝ r−1.0 for the short distances (r < 50 km) and as g(r) ∝ r−0.8 for the larger distances (r < 50 km). A frequency-dependent quality factor, inverse of the seismic attenuation parameter, Q(f) = 160f/fref0. 35 (where fref = 1.0 Hz), is combined to the geometrical spreading. The source excitation terms are defined at a selected reference distance with a magnitude- independent roll-off spectral parameter, κ 0.04 s and with a Brune stress drop parameter increasing with moment magnitude, from σ = 2 MPa for Mw = 2.0 to σ = 13 MPa for Mw = 4.5. For events M ≤ 4.5 (being Mwmax = 4.5 available in the data set) the stress parameters are obtained by correlating the empirical/excitation source spectra with the Brune spectral model as function of magnitude. For the larger magnitudes (Mw>4.5) outside the range available in the calibration data set where we do not have recorded data, we extrapolate our results through the calibration of the stress parameters of the Brune source spectrum over the Bindi et al. ground-motion prediction equation selected as a reference model (hereafter also ITA10).
Finally, the weak-motion-based model parameters are used through a stochastic approach in order to predict a set of region specific spectral ground-motion parameters (peak ground acceleration, peak ground velocity, and 0.3 and 1.0 Hz spectral acceleration) relative to the generic rock site as a function of distance between 10 and 250 km and magnitude between M 2.0 and M 7.0.
Description: This article has been accepted for publication in Geophysical Journal International ©: The Authors 2018. Published by Oxford University Press on behalf of the Royal Astronomical Society. All rights reserved. Uploaded in accordance with the publisher's self-archiving policy.
Thu, 01 Mar 2018 00:00:00 GMThttp://hdl.handle.net/2122/122972018-03-01T00:00:00Z
- Ground-motion scaling in the Western Alpshttp://hdl.handle.net/2122/2473Title: Ground-motion scaling in the Western Alps
Authors: Morasca, P.; Malagnini, L.; Akinci, A.; Spallarossa, D.; Herrmann, R. B.
Abstract: In order to empirically obtain the scaling relationships
for the high-frequency ground motion in
the Western Alps (NW Italy), regressions are carried
out on more than 7500 seismograms from 957 regional
earthquakes. The waveforms were selected from the
database of 6 three-component stations of the RSNI
(Regional Seismic network of Northwestern Italy). The
events,MW ranging between 1.2 and 4.8, were recorded
within a hypocentral distance of 200 km during the
time period: 1996–2001. The peak ground velocities
are measured in selected narrow-frequency bands, between
0.5 and 14 Hz. Results are presented in terms of
a regional attenuation function for the vertical ground
motion, a set of vertical excitation terms at the reference
station STV2 (hard-rock), and a set of site terms
(vertical and horizontal), all relative to the vertical component
of station STV2.
The regional propagation of the ground motion is
modeled after quantifying the expected duration of the
seismic motion as a function of frequency and hypocentral
distance. A simple functional form is used to take into account both the geometrical and the anelastic attenuation:
a multi-variable grid search yielded a quality
factor Q( f ) = 310 f 0.20, together with a quadri-linear
geometrical spreading at low frequency. A simpler, bilinear
geometrical spreading seems to be more appropriate
at higher frequencies (f > 1.0 Hz). Excitation
terms are matched by using a Brune spectral model
with variable, magnitude-dependent stress drop: at Mw
4.8, we used σ = 50MPa. A regional distanceindependent
attenuation parameter is obtained (κ0 = 0.012 s) by modelling the average spectral decay at high
frequency of small earthquakes.
In order to predict the absolute levels of ground
shaking in the region, the excitation/attenuation model
is used through the Random Vibration Theory (RVT)
with a stochastic point-source model. The expected
peak-ground accelerations (PGA) are compared with
the ones derived by Ambraseys et al. (1996) for the
Mediterranean region and by Sabetta and Pugliese
(1996) for the Italian territory.
Sun, 01 Jan 2006 00:00:00 GMThttp://hdl.handle.net/2122/24732006-01-01T00:00:00Z