Earth-printshttp://www.earth-prints.orgThe DSpace digital repository system captures, stores, indexes, preserves, and distributes digital research material.Mon, 26 Aug 2019 06:20:52 GMT2019-08-26T06:20:52Z50681Ground-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/2122/37622004-01-01T00:00:00ZScaling Earthquake Ground Motions in Western Anatolia, Turkeyhttp://hdl.handle.net/2122/9495Title: Scaling Earthquake Ground Motions in Western Anatolia, Turkey
Authors: Akinci, A.; D'Amico, S.; Malagnini, L.; Mercuri, A.
Abstract: In this study, we provide a complete description of the ground-motion characteristics of
the western Anatolia region of Turkey. The attenuation of ground motions with distance
and the variability in excitation with magnitude are parameterized using three-component
0.25-10.0 Hz earthquake ground motions at distances of 15 - 250 km. The data set is
comprised of more than 11,600 three-component seismograms from 902 regional
earthquakes of local magnitude (ML) 2.5 to 5.8, recorded during the Western Anatolia
Seismic Recording Experiment (WASRE) between November 2002 and October 2003.
We used regression analysis to relate the logarithm of measured ground motion to the
excitation, site, and propagation effects. Instead of trying to reproduce the details of the
high-frequency ground motion in the time domain, we use a source model and a regional
scaling law to predict the spectral shape and amplitudes of ground motion at various
source-receiver distances. We fit a regression to the peak values of narrow bandpass
filtered ground velocity time histories, and root mean square and RMS-average Fourier
spectral amplitudes for a range of frequencies to define regional attenuation functions
characterized by piece-wise linear geometric spreading (in log-log space) and a
frequency-dependent crustal Q(f). An excitation function is also determined, which
contains the competing effects of an effective stress parameter k0 and a high-frequency
attenuation term exp(-k0f). The anelastic attenuation coefficient for the entire region is
given by Q(f) = 180f 0.55. The duration of motion for each record is defined as the value
that yields the observed relationship between time-domain and spectral-domain
amplitudes, according to random process theory. Anatolian excitation spectra are
calibrated for our empirical results by using a Brune model with a stress drop of 10 MPa for the largest event in our data set (Mw 5.8) and a near-surface attenuation parameter of
κ =0.045 s.
These quantities, together with the effective duration of ground motion in the region, are
used to estimate the peak ground motion (PGA, PGV). Using stochastic ground motion
simulations, we predict the absolute level of ground shaking and compare them with
strong-motion data in the region. The attenuation of simulated ground motion is
compared with recent global and regional ground motion prediction equations (GMPEs).
The performance of the stochastic model is also tested against small and intermediatesized
earthquakes (the M3.9 11 November 2007, M5.9 17 October 2005 and M5.7 20
October 2005 Izmir-Urla earthquakes) recorded by strong motion stations in the National
Strong Ground Motion Network (operated by the Earthquake Department of the Disaster
and Emergency Management Presidency, AFAD).
Tue, 01 Jan 2013 00:00:00 GMThttp://hdl.handle.net/2122/94952013-01-01T00:00:00ZImplications 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/2122/109632014-01-01T00:00:00ZTreatment 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/2122/37482005-01-01T00:00:00ZHigh-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/2122/29542001-12-01T00:00:00ZThe 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/2122/89922013-09-25T00:00:00ZResults 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/2122/109612017-01-01T00:00:00ZMEASUREMENTS OF INTRINSIC AND SCATTERING SEISMIC ATTENUATION IN THE CRUSThttp://hdl.handle.net/2122/6949Title: MEASUREMENTS OF INTRINSIC AND SCATTERING SEISMIC ATTENUATION IN THE CRUST
Authors: Del Pezzo, E.; Ibanez, J.; Morales, J.; Akinci, A.; Maresca, R.
Abstract: Intrinsic and scattering attenuation parameters, Q~ and Qs, have been measured in three different tectonic areas for local and shallow earthquakes located close to the receiver. The approach developed by Wennerberg (1993), which takes into account the numerical correction of the coda-Q parameter for the multiple scat- tering formulation of Zeng, was used to infer from the estimates of coda Q and direct S-wave Q the intrinsic (Qi) and scattering (Qs) Q values. Results for 1 to 12 Hz range show that Q~ is comparable to Qs for the Etna volcano and for the Campi Flegrei area, while Qi for the tectonically active area of Granada is lower than Qs. Coda Q is close to intrinsic Q, suggesting that, at least in the crust, coda Q is a good estimate of the intrinsic Q. Volcanic areas show a reasonable higher degree of heterogeneity, if compared with the nonvolcanic area of Granada.
Sun, 01 Oct 1995 00:00:00 GMThttp://hdl.handle.net/2122/69491995-10-01T00:00:00ZA Ten-Year Earthquake Occurrence Model for Italyhttp://hdl.handle.net/2122/8200Title: A Ten-Year Earthquake Occurrence Model for Italy
Authors: Marzocchi, W.; Amato, A.; Akinci, A.; Chiarabba, A.; Lombardi, A.; Pantosti, D.; Boschi, E.
Abstract: The recent Mw 6.3 destructive L’Aquila earthquake has further stimulated the improvement of the Italian operational earthquake forecasting capability
at different time intervals. Here, we describe a medium-term (10-year) forecast model
for Mw ≥5:5 earthquakes in Italy that aims at opening new possibilities for risk mitigation purposes. While a longer forecast yielded by the national seismic-hazard map
is the primary component in establishing the building code, a medium-term earthquake forecast model may be useful to prioritize additional risk mitigation strategies
such as the retrofitting of vulnerable structures. In particular, we have developed an
earthquake occurrence model for a 10-year forecast that consists of a weighted average of time-independent and different types of available time-dependent models,
based on seismotectonic zonations and regular grids. The inclusion of time-dependent
models marks a difference with the earthquake occurrence model of the national seismic-hazard map, and it is motivated by the fact that, at the 10-year scale, the contribution of time-dependency in the earthquake occurrence process may play a
major role. The models are assembled through a simple averaging scheme whereby
each model is weighted through the results of a retrospective testing phase similar to
the ones carried out in the framework of the Collaboratory for the Study of Earthquake
Predictability. In this way, the most hazardous Italian areas in the next ten years will
arise from a combination of distinct models that place more emphasis on different
aspects of the earthquake occurrence process, such as earthquake clustering, historical
seismic rate, and the presence of delayed faults capable of large events. Finally, we
report new challenges and possible developments for future updating of the model.
Sun, 01 Jan 2012 00:00:00 GMThttp://hdl.handle.net/2122/82002012-01-01T00:00:00ZStrong-Ground-Motion Simulation of the 6 April 2009 L’Aquila, Italy, Earthquakehttp://hdl.handle.net/2122/8199Title: Strong-Ground-Motion Simulation of the 6 April 2009 L’Aquila, Italy, Earthquake
Authors: Ugurhan, B.; Askan, A.; Akinci, A.; Malagnini, L.
Abstract: On 6 April 2009, an earthquake of Mw 6:13 (Herrmann et al., 2011)
occurred in central Italy, close to the town of L’Aquila. Although the earthquake
is considered to be a moderate-size event, it caused extensive damage to the surrounding area. The earthquake is identified with significant directivity effects: highamplitude, short-duration motions are observed at the stations that are oriented along
the rupture direction, whereas low-amplitude, long-duration motions are observed at
the stations oriented in the direction opposite to the rupture. The complex nature of the
earthquake combined with its damage potential brings the need for studies that assess
the seismological characteristics of the 2009 L’Aquila mainshock.
In this study, we present the strong-ground-motion simulation of this particular
earthquake using a stochastic finite-fault model with a dynamic corner frequency approach. For modeling the resulting ground motions, we choose two finite-fault source
models that take into account the source complexity of the L’Aquila mainshock. In
order to test the sensitivity of ground-motion parameters to the seismic wave attenuation parameters, we use two different attenuation models obtained in the study region
using weak-motion and strong-motion databases. Comparisons are made between the
attenuation of synthetics and ground-motion prediction equations (GMPEs). Synthetic
ground motions are further compared with the observed ones in terms of Fourier
amplitude and response spectra at 21 strong-ground-motion stations that recorded
the mainshock within an epicentral distance of 100 km. The spatial distribution of
shaking intensity obtained from the “Did You Feel It?” project and site survey results
are compared with the spatial distributions of simulated peak ground-motion intensity
parameters. Our results show that despite the limitations of the method in simulating
the directivity effects, the stochastic finite-fault model seems an effective and fast tool
to simulate the high-frequency portion of ground motion.
Sun, 01 Jan 2012 00:00:00 GMThttp://hdl.handle.net/2122/81992012-01-01T00:00:00ZHAZGRIDX: 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/2122/66982010-06-25T00:00:00ZSeparation 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/2122/4092005-01-01T00:00:00ZA 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/2122/29132007-06-01T00:00:00ZUncertainty analysis for seismic hazard in Northern and Central Italyhttp://hdl.handle.net/2122/1118Title: Uncertainty analysis for seismic hazard in Northern and Central Italy
Authors: Lombardi, A. M.; Akinci, A.; Malagnini, L.; Mueller, C. S.
Abstract: In this study we examine uncertainty and parametric sensitivity of Peak Ground Acceleration (PGA) and 1-Hz
Spectral Acceleration (1-Hz SA) in probabilistic seismic hazard maps (10% probability of exceedance in 50
years) of Northern and Central Italy. The uncertainty in hazard is estimated using a Monte Carlo approach to
randomly sample a logic tree that has three input-variables branch points representing alternative values for bvalue,
maximum magnitude (Mmax) and attenuation relationships. Uncertainty is expressed in terms of 95% confidence
band and Coefficient Of Variation (COV). The overall variability of ground motions and their sensitivity
to each parameter of the logic tree are investigated. The largest values of the overall 95% confidence band
are around 0.15 g for PGA in the Friuli and Northern Apennines regions and around 0.35 g for 1-Hz SA in the
Central Apennines. The sensitivity analysis shows that the largest contributor to seismic hazard variability is uncertainty
in the choice of ground-motion attenuation relationships, especially in the Friuli Region (∼0.10 g) for
PGA and in the Friuli and Central Apennines regions (∼0.15 g) for 1-Hz SA. This is followed by the variability
of the b-value: its main contribution is evident in the Friuli and Central Apennines regions for both 1-Hz SA
(∼0.15 g) and PGA (∼0.10 g). We observe that the contribution of Mmax to seismic hazard variability is negligible,
at least for 10% exceedance in 50-years hazard. The overall COV map for PGA shows that the uncertainty
in the hazard is larger in the Friuli and Northern Apennine regions, around 20-30%, than the Central Apennines
and Northwestern Italy, around 10-20%. The overall uncertainty is larger for the 1-Hz SA map and reaches 50-
60% in the Central Apennines and Western Alps.
Thu, 01 Dec 2005 00:00:00 GMThttp://hdl.handle.net/2122/11182005-12-01T00:00:00ZCharacterization 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/2122/67002011-01-01T00:00:00ZEarthquake 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/2122/34212007-07-01T00:00:00ZUncertainties 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/2122/67042010-01-01T00:00:00ZProgetto 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/2122/37672007-12-01T00:00:00ZA 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/2122/23062006-01-01T00:00:00ZPhysics‐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/2122/107722017-01-01T00:00:00ZDETERMINISTIC SCENARIOS AS INPUT MOTION FOR LOSS ASSESSMENThttp://hdl.handle.net/2122/3299Title: DETERMINISTIC SCENARIOS AS INPUT MOTION FOR LOSS ASSESSMENT
Authors: Ameri, G.; Akinci, A.; Cocco, M.; Cultrera, G.; Franceschina, G.; Lombardi, A.; Pacor, F.; Pessina, V.; Zonno, G.
Abstract: A predominantly deterministic viewpoint has been adopted for computing seismic ground motion both for urban areas (SP10) and infrastructures loss modeling (SP11) at three selected areas: the cities of Lisbon (Portugal) and Thessaloniki (Greece), and the metropolis of Istanbul (Turkey). The generation of earthquake ground motion scenarios involves both the particular choice of earthquake sources with associated fault rupture parameters, and the ensuing ground motion field calculated by an appropriate numerical tool, or empirically estimated, at a set of selected points within the urban area of interest.
Ground shaking values are predicted for rock conditions and for two distinct frequency bands, i.e. the high frequency range (from 1.0 Hz to 4-5 Hz) in the case of damage evaluation for the vast majority of ordinary building, and the low frequency (≤ 2 Hz) more appropriate for lifeline system damage assessment.
The advanced simulation techniques allowed to properly consider the finite fault effects and directivity, which imply extreme expected values, and they are capable of quantifying the spatial variability of the ground motion near the extended fault.
Thu, 19 Jul 2007 00:00:00 GMThttp://hdl.handle.net/2122/32992007-07-19T00:00:00ZGround-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/2122/29522005-04-01T00:00:00ZEstimating 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/2122/37532004-01-01T00:00:00ZSEPARATION OF SCATTERING AND INTRINSIC ATTENUATION IN SOUTHERN SPAIN AND WESTERN ANATOLIA (TURKEY)http://hdl.handle.net/2122/6945Title: SEPARATION OF SCATTERING AND INTRINSIC ATTENUATION IN SOUTHERN SPAIN AND WESTERN ANATOLIA (TURKEY)
Authors: Akinci, A.; Del Pezzo, E.; Ibanez, J.
Abstract: We have obtained a separation of intrinsic and scattering attenuation in two tectonically active areas of the Mediterranean Basin, southern Spain and western Anatolia, using the Multiple-Lapse Time Window Method. In southern Spain, Q(s) is predominant over Q(i) for frequencies lower than 4 Hz; between 4 and 8 Hz, results show similar scattering and intrinsic attenuation. For frequencies higher than 8 Hz, intrinsic attenuation is clearly dominant over scattering. L(e)(-1) does not change uniformly with frequency; it increases until 8 Hz and decreases at frequencies greater than 8 Hz. The integrated energy curves of western Anatolia do not show regular change with distance. For the first energy window (0-15 s), there is a clear increase of the energy with distances between 0 and 80 km, and then a decrease after 80 km. The fit of the experimental data in the full hypocentral distance range is not good. We divided the experimental energy curves into two different segments, 0-80 and 80-170 km. In 0-80 km, B-0 is close to 1 and the L(e)(-1) values are low (0.004-0.013). In the second distance range (80-170 km) intrinsic attenuation is predominant over scattering. Q(s)(-1) is more frequency-dependent than Q(i)(-1):f(-1.47) against f(-1.29). We observed that coda Q(-1) is equal to the observed Q(i)(-1) for intermediate frequencies, in both regions. However, Q(c)(-1) is really similar to Q(s)(-1) for short distances and is between Q(i) and Q(s) for long distances in southern Spain at low frequencies. Q(c) is similar to the observed Q(t) in both regions at high frequencies. The poor fit of the simulated curves with experimental data can be explained by introducing geometrical spreading values different to those used here. It is necessary to improve the model used by taking into account phenomena like non-isotropic scattering, variation of attenuation with depth, the presence of surface waves or a geometrical spreading value different to the theoretical one used.
Mon, 01 May 1995 00:00:00 GMThttp://hdl.handle.net/2122/69451995-05-01T00:00:00ZCharacteristics 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/2122/114292016-01-01T00:00:00ZM ≥ 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/2122/107082016-04-01T00:00:00ZInvestigating 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/2122/108602016-01-01T00:00:00ZINGV final report of the project: Large earthquake faulting and implications for the Seismic Hazard Assessment in Europe: the Izmit-Duzce earthquake sequence of August-November 1999 (Turkey, Mw 7.4, 7.1)http://hdl.handle.net/2122/1046Title: INGV final report of the project: Large earthquake faulting and implications for the Seismic Hazard Assessment in Europe: the Izmit-Duzce earthquake sequence of August-November 1999 (Turkey, Mw 7.4, 7.1)
Authors: Pantosti, D.; Pucci, S.; Palyvos, N.; De Martini, P. M.; D'Addezio, G.; Akinci, A.; Zabci, C.; Collins, P.; Storia Geofisica Ambiente; Fantucci, R.
Sun, 01 Jan 2006 00:00:00 GMThttp://hdl.handle.net/2122/10462006-01-01T00:00:00ZImplementing 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/2122/107742016-01-01T00:00:00ZNucleation 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/2122/107732017-08-01T00:00:00ZImaging 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/2122/66992010-02-01T00:00:00ZUnbiased 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/2122/24722006-01-01T00:00:00ZThe 2012 Ferrara seismic sequence: Regional crustal structure, earthquake sources, and seismic hazardhttp://hdl.handle.net/2122/9545Title: The 2012 Ferrara seismic sequence: Regional crustal structure, earthquake sources, and seismic hazard
Authors: Malagnini, L.; Herrmann, R. B.; Munafò, I.; Buttinelli, M.; Anselmi, M.; Akinci, A.; Boschi, E.
Abstract: Inadequate seismic design codes can be dangerous, particularly when they underestimate the true hazard. In this study we use data from a sequence of moderate-sized earthquakes in northeast Italy to validate and test a regional wave propagation model which, in turn, is used to under- stand some weaknesses of the current design spectra. Our velocity model, while regionalized and somewhat ad hoc, is consistent with geophysical observations and the local geology. In the 0.02–0.1 Hz band, this model is validated by using it to calculate moment tensor solutions of 20 earth- quakes (5.6 MW 3.2) in the 2012 Ferrara, Italy, seismic sequence. The seismic spectra observed for the relatively small main shock significantly exceeded the design spectra to be used in the area for critical structures. Observations and synthetics reveal that the ground motions are dominated by long-duration surface waves, which, apparently, the design codes do not adequately anticipate. In light of our results, the present seismic hazard assessment in the entire Pianura Padana, including the city of Milan, needs to be re-evaluated. Citation: Malagnini, L., R. B. Herrmann, I. Munafò, M. Buttinelli, M. Anselmi, A. Akinci, and E. Boschi (2012), The 2012 Ferrara seismic sequence: Regional crustal structure, earthquake sources, and seismic hazard, Geophys. Res. Lett., 39, L19302, doi:10.1029/ 2012GL053214.
Sun, 01 Jan 2012 00:00:00 GMThttp://hdl.handle.net/2122/95452012-01-01T00:00:00ZWeak-motion-based predictive relationships for the ground motion in Israelhttp://hdl.handle.net/2122/2912Title: Weak-motion-based predictive relationships for the ground motion in Israel
Authors: Meirova, T.; Hofstetter, A.; Ben-Avraham, Z.; Steinberg, D.; Malagnini, L.; Akinci, A.
Abstract: We perform a regional study in order to provide the seismic hazard community of Israel with new predictive relationships for the earthquake-induced ground motion in Israel. This work is essential for the development of a new generation of hazard maps, for the planning of the development of the Israel’s region, and the design of earthquake resistant structures and facilities. The main goals of our work is to provide a quantitative description of the expected ground motion within the Israel region, as a function of the hypocentral distance and frequency of motion. For this purpose we use the regression technique that was proposed by Yazd (1993), Herrmann (1999), Raoof et al., (1999) and Malagnini et al.,(2002). The undoubted advantage of this method is the possibility to use for analysis the data of frequent, small earthquakes that are typical for this region.
In our analyses we use 4786 waveforms recorded by 30 stations of the Israel Seismic Network from 2000 to 2005. We restricted our analysis to events recorded at 10 or more stations, resulting in 330 appropriate earthquakes, with a magnitude range between 1.8 and 5.2. We derive the empirical excitation, site, and regional attenuation terms by regressing the peak amplitudes of narrowband-filtered seismograms around the shear-waves arrivals, and the rms Fourier spectral amplitudes taken around the specific sampling frequency. A theoretical modeling effort is performed by using Random Vibration Theory (RVT) on the parameters derived from the observations. For prediction we use the quality parameter Q(f)=270f^0.7 , whereas the geometrical spreading g(r) used in the model was parameterized as a bilinear, piecewise function: r^-0.95 for r<60 km , and r^-0.5 for r>60 km . The modeling of the excitation terms is based on the Brune’s source spectrum.
Mon, 01 Jan 2007 00:00:00 GMThttp://hdl.handle.net/2122/29122007-01-01T00:00:00ZEffect 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/2122/42302008-01-01T00:00:00ZWeak-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/2122/42192008-01-01T00:00:00ZLoss 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/2122/56002009-04-01T00:00:00ZGround motion scaling in the Marmara region, Turkeyhttp://hdl.handle.net/2122/2471Title: Ground motion scaling in the Marmara region, Turkey
Authors: Akinci, A.; Malagnini, L.; Herrmann, R. B.; Gok, R.; Sorensen, M. B.
Abstract: Predictive relationships for the ground motion in the Marmara region (northwestern Turkey)
are parametrized after regressing three-component waveforms from regional earthquakes, in
the frequency range: 0.4–15.0 Hz, and in the distance range: 10–200 km. The data set consists
of 2400 three-component recordings from 462 earthquakes, recorded at 53 stations. Moment
magnitudes, Mw, range between 2.5 and 7.2. The largest event for which we have waveforms
available (Mw 7.2) occurred in Duzce on 1999 November 12. The aftershocks of that earthquake,
together with the aftershocks of the 1999 August 17 Izmit event (Mw = 7.4), are
included in the dataset.
Regressions are performed, independently, on Fourier velocity spectra and on peak ground
velocities, for a large number of sampling frequencies. A simple model is used to relate the
logarithm of the measured ground motion to excitation, site, and propagation terms. Results
obtained for peak velocities are used to define a piecewise continuous geometrical spreading
function, g(r), a frequency-dependent Q(f ), and a distance-dependent duration function. The
latter is used, through random vibration theory (RVT), in order to predict time-domain characteristics
(i.e. peak values) of the ground motion. The complete model obtained for the peak
ground motion was used to match the results of the regressions on the Fourier amplitudes.
Fourier velocity spectra for the combined horizontal motion are best fit by a hinged quadrilinear
geometrical spreading function for observations in the 10–200 km hypocentral distance
ranges as a function of frequency: f < 1.0 Hz, r−1.2 for r ≤ 30 km; r−0.7 for 30 < r ≤ 60 km;
r−1.4 for 60<r ≤100 km; r−0.1 for r >100, f ≥1.0 Hz, r−1.0 for r ≤30 km; r−0.6 for 30<r ≤ 60 km; r−0.9 for 60<r ≤100 km; r−0.1 for r >100 km. The frequency-dependent crustal shearwave
quality factor Q (f ) coefficient Q( f )=180 f 0.45. The T (5–75 per cent) duration window
provides good agreement between observed and predicted peak values. By modelling the
behaviour of the small earthquakes at high frequency, we also quantified a regional parameter
κ = 0.055 s. Spectral models with one single-corner frequency (Brune), and with two-corner
frequencies (Atkinson and Silva) fit the observed high-frequency excitation levels equallywell,
whereas the model by Atkinson and Silva fits the low-frequency observations slightly better
than Brune’s.
RVT is used to predict the absolute levels of ground shaking, following Boore’s implementation
of the stochastic ground motion model (Boore’s SMSIM codes). Our regional empirical
predictive relationships are compared to the ones adopted in several regions of the world, from
California to Western United States.
Sun, 01 Jan 2006 00:00:00 GMThttp://hdl.handle.net/2122/24712006-01-01T00:00:00ZWhat is the impact of the August 24, 2016 Amatrice earthquake on the seismic hazard assessment in central Italy?http://hdl.handle.net/2122/10698Title: What is the impact of the August 24, 2016 Amatrice earthquake on the seismic hazard assessment in central Italy?
Authors: Murru, Maura; Taroni, Matteo; Akinci, Aybige; Falcone, Giuseppe
Abstract: The recent Amatrice strong event (Mw6.0) occurred on August 24, 2016 in Central Apennines (Italy) in a seismic gap zone, motivated us to study and provide better understanding of the seismic hazard assessment in the macro area defined as “Central Italy”. The area affected by the sequence is placed between the Mw6.0 1997 Colfiorito sequence to the north (Umbria-Marche region) the Campotosto area hit by the 2009 L’Aquila sequence Mw6.3 (Abruzzo region) to the south. The Amatrice earthquake occurred while there was an ongoing effort to update the 2004 seismic hazard map (MPS04) for the Italian territory, requested in 2015 by the Italian Civil Protection Agency to the Center for Seismic Hazard (CPS) of the Istituto Nazionale di Geofisica e Vulcanologia INGV. Therefore, in this study we brought to our attention new earthquake source data and recently developed ground-motion prediction equations (GMPEs). Our aim was to validate whether the seismic hazard assessment in this area has changed with respect to 2004, year in which the MPS04 map was released. In order to understand the impact of the recent earthquakes on the seismic hazard assessment in central Italy we compared the annual seismic rates calculated using a smoothed seismicity approach over two different periods; the Parametric Catalog of the Historical Italian earthquakes (CPTI15) from 1871 to 2003 and the historical and instrumental catalogs from 1871 up to 31 August 2016. Results are presented also in terms of peak ground acceleration (PGA), using the recent ground-motion prediction equations (GMPEs) at Amatrice, interested by the 2016 sequence.
Fri, 01 Jan 2016 00:00:00 GMThttp://hdl.handle.net/2122/106982016-01-01T00:00:00ZStrong 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/2122/37642002-01-01T00:00:00ZControl of pore fluid pressure diffusion on fault failure mode:Insights from the 2009 L’Aquila seismic sequencehttp://hdl.handle.net/2122/8198Title: Control of pore fluid pressure diffusion on fault failure mode:Insights from the 2009 L’Aquila seismic sequence
Authors: Malagnini, L.; Lucente, F.; De Gori, P.; Akinci, A.; Munafò, I.
Abstract: The MW 6.13 L’Aquila earthquake ruptured the Paganica fault on 2009/04/06 at
01:32 UTC, and started a strong sequence of aftershocks. For the first four days, the region
north of the hypocenter of the main quake was shaken by three large events (MW 5.0)
that ruptured different patches of the Monti della Laga fault (hereafter “Campotosto”).
In our hypothesis, these aftershocks were induced by a dramatic reduction in the fault’s
shear strength due to a pulse of pore fluid pressure released after the L’Aquila main
earthquake. Here we model the time evolution of the pore fluid pressure northward from
the main hypocenter. We show that, during the sequence, the Campotosto fault failed in
multiple episodes, when the specific patches/asperities underwent fluid pressure-related
strength reductions of 7–10 MPa. Although such drops in strength are very large in
amplitude, the contribution of other weakening mechanisms (perturbations of the Coulomb
shear stress, and/or dynamic stresses induced by passing seismic waves) cannot be ruled
out by our observations. However, the Coulomb shear stress variations either had negative
amplitudes down to 0.2 MPa (i.e., tended to inhibit further seismic activity), or had
very small positive amplitudes (<0.05 MPa). Paleoseismological evidence supports the
hypothesis that larger events (MW 6.5–7) have occurred on the Paganica fault [EMERGEO
Working Group, 2009], whereas Lucente et al. [2010] concluded that an important
migration of pore fluids characterized the preparatory phase of the L’Aquila main shock.
Consequently, the MW 6.13 L’Aquila earthquake may be analogous, at a larger scale,
to one of the three Campotosto largest aftershocks. The complex behavior observed for the
L’Aquila-Campotosto fault system seems to be common to other seismogenic structures
in the Central Apennines (e.g., the Umbria-Marche fault system), and need to be taken into
consideration for the assessment of seismic hazard.
Sun, 01 Jan 2012 00:00:00 GMThttp://hdl.handle.net/2122/81982012-01-01T00:00:00ZStrong 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/2122/42182008-01-01T00:00:00ZGround-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/2122/24732006-01-01T00:00:00ZSeismological 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/2122/52732003-08-01T00:00:00ZEffect 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/2122/55902009-04-01T00:00:00ZCharacteristics 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/2122/29532002-08-01T00:00:00ZEvaluation 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/2122/37472004-01-01T00:00:00ZAttenuative 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/2122/37522004-01-01T00:00:00ZCharacteristics 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/2122/58872010-01-01T00:00:00ZThe 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