DSpace Collection:
http://hdl.handle.net/2122/241
2014-04-16T04:18:01ZThe role of radiation damping in the modeling of repeated earthquake events
http://hdl.handle.net/2122/8666
Title: The role of radiation damping in the modeling of repeated earthquake events
Authors: Crupi, P.; Università degli Studi di Bari, Bari, Italy; Bizzarri, A.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Bologna, Bologna, Italia
Abstract: We have investigated the role of the radiation damping term (RDT) on
repeated earthquake ruptures by modeling the faulting process through a
single one-dimensional analog fault system governed by different
constitutive laws. The RDT expresses the energy lost by the seismic waves.
The RDT is inherently accounted for in more elaborated, fully dynamic
models of extended fault, whereas it is neglected in one-dimensional fault
models. In this study, we adopt various formulations of the laboratoryderived
rate-dependent and state-dependent friction constitutive laws: the
Dieterich-Ruina law, the Ruina-Dieterich law and the Chester and Higgs
law. Our numerical results clearly indicate that the RDT significantly
affects the system dynamics. More specifically, the more the RDT is
effective, the more frequent the slip failures are (with a cycle-time reduction
of ca. 30%). We also show that inclusion of the RDT tends to promote
smaller but more frequent earthquake instabilities, irrespective of the
choice of the governing law. Our data shed light on the limitations implied
by the conventional formulation of the equation of motion for the spring
system, in which the energy radiation is ignored.2012-12-31T23:00:00ZPower-law frequency distribution of H/V spectral ratio of seismic signals: Evidence for a critical crust
http://hdl.handle.net/2122/8664
Title: Power-law frequency distribution of H/V spectral ratio of seismic signals: Evidence for a critical crust
Authors: Signanini, P.; Università di Chieti e Pescara “G. D’Annunzio”, Dipartimento Geotecnologie per l’Ambiente e il Territorio, Chieti Scalo, Italy; De Santis, A.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma2, Roma, Italia
Abstract: We analyse records from several seismic stations in Central Italy (including some with multiple recording sites) for the statistical properties of spectra of both noise and earthquake signals. The main result is that the power-law scaling of most of the spectral H/V ratio statistical distributions leads to a so-called heavy tail. This is interpreted as a statistical distribution with a fractal dimension of about 2, which is almost certainly caused by
a porous percolating medium beneath the stations due to some universal property of the crustal rocks crossed by the elastic waves propagation suggesting that the uppermost crust is in a critical state.2012-03-06T23:00:00ZIntegrating geologic fault data into tsunami hazard studies
http://hdl.handle.net/2122/8663
Title: Integrating geologic fault data into tsunami hazard studies
Authors: Basili, R.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma1, Roma, Italia; Tiberti, M. M.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma1, Roma, Italia; Kastelic, V.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma1, Roma, Italia; Romano, F.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma1, Roma, Italia; Piatanesi, A.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma1, Roma, Italia; Selva, J.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Bologna, Bologna, Italia; Lorito, S.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma1, Roma, Italia
Abstract: We present the realization of a fault-source data set designed to become the starting point in regional-scale tsunami hazard studies. Our approach focuses on the parametric fault characterization in terms of geometry, kinematics, and assessment of activity rates, and includes a systematic classification in six justification levels of epistemic uncertainty related with the existence and behaviour of fault sources. We set up a case study in the central Mediterranean Sea, an area at the intersection of the European, African, and Aegean plates, characterized by a complex and debated tectonic structure and where several tsunamis occurred in the past. Using tsunami scenarios of maximum wave height due to crustal earthquakes (Mw=7) and subduction earthquakes (Mw=7 and Mw=8), we illustrate first-order consequences of critical choices in addressing the seismogenic and tsunamigenic potentials of fault sources. Although tsunamis generated by Mw=8 earthquakes predictably affect the entire basin, the impact of tsunamis generated by Mw=7 earthquakes on either crustal or subduction fault sources can still be strong at many locales. Such scenarios show how the relative location/orientation of faults with respect to target coastlines coupled with bathymetric features suggest avoiding the preselection of fault sources without addressing their possible impact onto hazard analysis results.2013-04-18T22:00:00ZProbabilistic seismic hazard at Mt. Etna (Italy): The contribution of local fault activity in mid-term assessment
http://hdl.handle.net/2122/8146
Title: Probabilistic seismic hazard at Mt. Etna (Italy): The contribution of local fault activity in mid-term assessment
Authors: Azzaro, R.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Catania, Catania, Italia; D'Amico, S.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Catania, Catania, Italia; Peruzza, L.; Istituto Nazionale di Oceanografia e Geofisica Sperimentale; Tuvè, T.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Catania, Catania, Italia
Abstract: In this work, we tackle the problem of seismic hazard at Etna deriving from the recurrent seismogenic activity of local faults, by adopting two independent methods based on probabilistic approaches. We assess the hazard in terms of macroseismic intensity and represent the occurrence probability calculated for different exposure
times both on maps and at fault scale. Seismic hazard maps obtained by applying the “site approach” through the SASHA code and a new probabilistic attenuation model, indicate the eastern flank of the volcano as the most hazardous, with expected intensity (Iexp) in 50 years (i.e. the standard exposure time adopted in the seismic regulations) ranging from degrees IX to X EMS. In shorter exposure periods (20, 10, 5 years), values of Iexp up to IX are also reached in the same area, but they are clearly determined by the earthquakes generated by the Timpe fault system. In order to quantify the contribution of local
seismogenic sources to the hazard of the region, we reconstruct the seismic history of each fault and calculate with SASHA the probability that earthquakes of a given intensity may be generated in different exposure times. Results confirm the high level of hazard due to the S. Tecla, Moscarello and Fiandaca faults especially
for earthquakes of moderate intensity, i.e. VI≤I0≤VII, with probabilities respectively exceeding 50% and 20% in 10 years, and 30% and 10% in 5 years. Occurrence probability of major events (I0≥VIII) at the fault scale has also been investigated by statistics on intertimes. Under stationary assumptions we obtain a probability of 6.8% in 5 years for each structure; by introducing the time-dependency (time elapsed since the last event occurred on each fault) through a BPT model, we identify the Moscarello and S. Tecla faults as the most probable sources to be activated in the next 5 years (2013–2017). This result may represent a useful indication to establish
priority criteria for actions aimed at reducing seismic risk at a local scale.2012-12-31T23:00:00ZProject S1: Analysis of the seismic potential in Italy for the evaluation of the seismic hazard
http://hdl.handle.net/2122/7958
Title: Project S1: Analysis of the seismic potential in Italy for the evaluation of the seismic hazard
Authors: Barba, S.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma1, Roma, Italia; Doglioni, C.; Sapienza Università di Roma
Abstract: The project S1 was aimed at (a) collecting new data and to update the existing databases needed to quantify seismic hazard; (b) promoting new studies on specific fields of knowledge and less-explored areas of Italy; (c) testing new approaches to evaluate seismic potential; (d) bounding slip rate values to use within probabilistic hazard estimates; and (e) preparing the way towards a future seismic hazard map of Italy. It was designed with three scientific parts – nationwide basic data, rheology, and field studies – and implemented into four tasks: 1) earthquake geodesy and modeling, 2) seismological data and earthquake statistics, 3) earthquake geology, and 4) tsunamis.
Although with many difficulties and some delay, described in the appropriate section, all the above objectives have generally been accomplished.
New observations were collected through original fieldwork and more sophisticated analyses were performed on existing data. Datasets needed for the seismic hazard estimates were updated at various levels by reducing both epistemic and aleatory uncertainties. New studies were carried out on specific fields of knowledge, e.g. addressing the repeatability of geodetic and stress data measurements or the seismogenic behavior of misoriented faults. Studies on less-explored areas were stimulated, and faults, whose seismic potential was not previously accounted for, were mapped and/or parameterized in the Ionian and Adriatic Seas, in Calabria, Sicily and the Southwestern Alps. Independent approaches to evaluate the seismic potential were tested, and a large effort toward homogenization and verifiability was made. The substantial improvements of nationwide datasets and understanding of the tectonic processes in large areas of the country set the basis for a significantly better assessment of seismic hazard.2010-06-29T22:00:00ZStatistics between mainshocks and foreshocks in Italy and Southern California
http://hdl.handle.net/2122/7292
Title: Statistics between mainshocks and foreshocks in Italy and Southern California
Authors: Marzocchi, W.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma1, Roma, Italia; Zhuang, J.; Institute of Statistical Mathematics, Tokyo, Japan
Abstract: The most used and accepted models for daily forecasts are based on short‐term space and time earthquake clustering for occurrence rates and on the Gutenberg‐ Richter law for the frequency‐magnitude. These models have been demonstrated to produce reliable prospective space‐time‐magnitude forecasts during an aftershock sequence, but their skill in forecasting mainshocks is still under discussion. This paper studies the foreshock statistics of the Italian and Californian seismicity in two ways: i) we compare the foreshock activity observed in real seismic catalogs and in synthetic catalogs derived from a pure Epidemic‐Type Aftershock Sequence (ETAS) model; ii) we analyze the triggering capability of earthquakes using different ETAS parameterizations, in order to check whether large events are triggered in the same way as regular earthquakes. The results indicate that the foreshock activity observed in the real catalogs is compatible with what is expected by the ETAS model. Moreover, we find that the empirical foreshock rates have an intrinsic variability due to limited sampling that may explain most of the differences found so far in different seismic catalogs.2010-12-31T23:00:00ZThe ETAS model for daily forecasting of Italian seismicity in the CSEP experiment
http://hdl.handle.net/2122/6419
Title: The ETAS model for daily forecasting of Italian seismicity in the CSEP experiment
Authors: Lombardi, A. M.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma1, Roma, Italia; Marzocchi, W.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma1, Roma, Italia
Abstract: This paper investigates the basic properties of the recent shallow seismicity in Italy through stochastic modeling and statistical methods. Assuming that the earthquakes are the realization of a stochastic point process, we model the occurrence rate density in space, time and magnitude by means of an Epidemic Type Aftershock Sequence (ETAS) model. By applying the maximum likelihood procedure, we estimates the parameters of the model that best fit the Italian instrumental catalog, recorded by the Istituto Nazionale di Geofisica e Vulcanologia (INGV) from April 16th 2005 to June 1st 2009. Then we apply the estimated model on a second independent dataset (June 1st 2009- Sep 1st 2009). We find that the model performs well on this second database, by using proper statistical tests. The model proposed in the present study is suitable for computing earthquake occurrence probability in real time and to take part in international initiatives such as the Collaboratory Study for Earthquake Predictability (CSEP). Specifically we have submitted this model for the daily forecasting of Italian seismicity above Ml4.0.2009-12-31T23:00:00ZRetrospective tests of the long-term earthquake forecasts submitted to CSEP-Italy Predictability experiment.
http://hdl.handle.net/2122/6392
Title: Retrospective tests of the long-term earthquake forecasts submitted to CSEP-Italy Predictability experiment.
Authors: Werner, M.; ETH Zurich; Zechar, J. D.; ETH Zurich; Marzocchi, W.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma1, Roma, Italia; Wiemer, S.; ETH Zurich
Abstract: On August 1, 2009, the global Collaboratory for the Study of Earthquake Predictability (CSEP) launched a prospective and comparative earthquake predictability experiment in Italy. The goal of this CSEP-Italy experiment is to test earthquake occurrence hypotheses that have been formalized as probabilistic earthquake forecasts over temporal scales that range from days to years. In the first round of forecast submissions, members of the CSEP- Italy Working Group presented 18 five-year and ten-year earthquake forecasts to the European CSEP Testing Center at ETH Zurich. We have considered here the twelve time-independent earthquake forecasts among this set, and evaluated them with respect to past seismicity data from two Italian earthquake catalogs. We present the results of the tests that measure the consistencies of the forecasts according to past observations. As well as being an evaluation of the time-independent forecasts submitted, this exercise provides insight into a number of important issues in predictability experiments with regard to the specification of the forecasts, the performance of the tests, and the trade-off between robustness of results and experiment duration. We conclude with suggestions for the design of future earthquake predictability experiments.2009-12-31T23:00:00ZThe Proportional Hazard Model applied to the CSEP testing area in Italy
http://hdl.handle.net/2122/6353
Title: The Proportional Hazard Model applied to the CSEP testing area in Italy
Authors: Faenza, L.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione CNT, Roma, Italia; Marzocchi, W.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma1, Roma, Italia
Abstract: This paper presents the strategies adopted to modify the Proportional Hazard Model (Faenza et al., 2003; Cinti et al., 2004) to fit the requirement for the forecast test within CSEP experiment. The model has been originally proposed to study the spatiotemporal distribution of the M 5.5+ seismicity in Italy, using two spatial models, a regular grid and a seismotectonic zonation. A prospective 10-years forecast test is already ongoing since 2005 and the results are available at the webpage (http://www.bo.ingv.it/ earthquake/
ITALY/forecasting/M5.5+/). In that test, we report the probability maps of M 5.5+ earthquake for the next 10 years for two spatial distributions. Since the original model is time-dependent, it is updated every year and immediately after the occurrence of a target event, e.g., Mw 5.5. Despite that prospective test is continuing and that the model updates probabilities different from CSEP experiments, we argue that a full evaluation of the model could be achieved only through the CSEP testing experiment, where the performances of different
models are compared using the same rules and tests. The major modification we have introduced into our model is the simulation of the expected numbers of events in the exposure time ∆τ. This is performed considering the probability that an event occurs in ∆τ and evaluating the change this will cause into the expected numbers of events. This procedure is implemented for the ﬁrst and the second generation of aftershocks.2009-12-31T23:00:00ZOccurrence probability of moderate to large earthquakes in Italy based on new geophysical methods
http://hdl.handle.net/2122/5877
Title: Occurrence probability of moderate to large earthquakes in Italy based on new geophysical methods
Authors: Slejko, D.; Istituto Nazionale di Oceanografia e di Geofisica Sperimentale, Sgonico (Trieste), Italy; Caporali, A.; University of Padua, Padua, Italy; Stirling, M.; GNS Science, Lower Hutt, New Zealand; Barba, S.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma1, Roma, Italia
Abstract: We develop new approaches to calculating 30-year probabilities for occurrence of moderate-to-large earthquakes in Italy. Geodetic techniques and finite-element modelling, aimed to reproduce a large amount of neotectonic data using thin-shell finite element, are used to separately calculate the expected seismicity rates inside seismogenic areas (polygons containing mapped faults and/or suspected or modelled faults). Thirty-year earthquake probabilities obtained from the two approaches show similarities in most of Italy: the largest probabilities are found in the southern Apennines, where they reach values between 10% and 20% for earthquakes of M W ≥ 6.0, and lower than 10% for events with an M W ≥ 6.5.2009-12-31T23:00:00Z