http://hdl.handle.net/2122/241 Thu, 20 Jun 2013 08:02:23 GMT 2013-06-20T08:02:23Z http://hdl.handle.net/2122/8719 Title: Is the initial thermal state of a fault relevant to its dynamic behavior? Authors: Bizzarri, A.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Bologna, Bologna, Italia; Crupi, P.; Università degli Studi di Bari "Aldo Moro" Abstract: The prediction of impending earthquakes undoubtedly remains one of the most pursued goals of modern seismology. Within the framework of a deterministic description of earthquake faulting, the initial state of the fault system and the choice of the governing model describing its rheological behavior play a fundamental role in the description of the earthquake recurrence. In classical models of faulting, this initial state is basically described by the initial shear-stress distribution (prior to the next earthquake event) and by the initial sliding velocity. In this paper, by assuming a rate-, state-, and temperature-dependent rheology, we investigate whether the initial thermal state of the fault can also have a significant role in earthquake dynamics. Our numerical results clearly demonstrate that the initial temperature greatly influences the cosesimic slip (and thus the earthquake magnitude), the released stress (and thus the radiated energy), and the interevent time (i.e., the earthquake recurrence). Despite the remaining issues on the concept of earthquake cyclicity, our results can contribute to the lively debate on the deterministic hazard assessment, illuminating that the temperature field also plays a fundamental role in earthquake dynamics, not only because it controls possible phase changes and the chemical environment of the fault zone, but also because it affects the response of a brittle fault and earthquake cycles. Fri, 31 May 2013 22:00:00 GMT http://hdl.handle.net/2122/8719 2013-05-31T22:00:00Z 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. Mon, 31 Dec 2012 23:00:00 GMT http://hdl.handle.net/2122/8666 2012-12-31T23:00:00Z 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. Tue, 06 Mar 2012 23:00:00 GMT http://hdl.handle.net/2122/8664 2012-03-06T23:00:00Z 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. Thu, 18 Apr 2013 22:00:00 GMT http://hdl.handle.net/2122/8663 2013-04-18T22:00:00Z http://hdl.handle.net/2122/8562 Title: CRISIS2008: A Flexible Tool to Perform Probabilistic Seismic Hazard Assessment Authors: Ordaz, M.; Martinelli, F.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Milano-Pavia, Milano, Italia; D'Amico, V.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Milano-Pavia, Milano, Italia; Meletti, C.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Milano-Pavia, Milano, Italia Abstract: In the frame of the Italian research project INGV-DPC S2 (http://nuovoprogettoesse2.stru.polimi.it/), funded by the Dipartimento della Protezione Civile (DPC; National Civil Protection Department) within the agreement 2007-2009, a tool for probabilistic seismic hazard assessment (PSHA) was developed. The main goal of the project was to provide a flexible computational tool for PSHA; the requirements considered essential for the success of the project included: • ability to handle both stationary and non-stationary earthquake time-occurrence models; • ability to use ground-motion prediction models that are not parametric equations but probabilistic "footprints" of the intensities generated by earthquakes of known magnitude and focal characteristics. Usually, these footprints are results of ground motion simulations. Some commonly used programs (e.g., FRISK, by McGuire, 1978; SEISRISK III, by Bender and Perkins, 1987) and more recent and state-of-the-art tools (e.g. OpenSHA, by Field et al., 2003, http://www.opensha.org; OpenQuake, http://openquake.org) for PSHA were analyzed. It was decided to focus on CRISIS2007, which was already a mature and well known application (e.g., Kalyan Kumar and Dodagoudar, 2011; Teraphan et al., 2011; D’Amico et al., 2012; see also http://ecapra.org/CRISIS-2007), but also suitable for additional development and evolution since its source code is freely available on request. The computational tool resulted in an extensive redesign and renovation of the previous CRISIS2007 version. CRISIS is a computer program for PSHA, originally developed in the late 1980's using Fortran as programming language (Ordaz, 1991). In this format, still without a graphical user interface (GUI), it was distributed as part of SEISAN tools (Ottemöller et al., 2011). Ten years later, a GUI was constructed, generating what was called CRISIS99 (Ordaz, 1999). In this version, all the graphic features were written in Visual Basic, but the computation engine remained a Fortran dynamic link library. The reason for the use of mixed-language programming was that computations in Visual Basic were extremely slow. Around 2007 the program was upgraded, in view of the advantages offered by the object-oriented technologies. An object-oriented programming language was required and the natural choice was Visual Basic.Net. In the new version (called CRISIS2007), both the GUI and the computation engine were written in the same language. Finally, in the frame of the mentioned S2 project, starting from 2008, the program was split into two logical layers: core (CRISIS Core Library) and presentation (CRISIS2008). In addition, a new presentation layer was developed for accessing the same functionalities via Web (CRISISWeb). It is worth noting that CRISIS has been mainly written by people that are, at the same time, PSHA practitioners. Therefore, the development loop has been relatively short, and most of the modifications and improvements have been made to satisfy the needs of the developers themselves. Tue, 30 Apr 2013 22:00:00 GMT http://hdl.handle.net/2122/8562 2013-04-30T22:00:00Z http://hdl.handle.net/2122/8552 Title: Coseismic deformation and source modeling of the May 2012 Emilia (Northern Italy) earthquakes Authors: Pezzo, G.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione CNT, Roma, Italia; Merryman Boncori, J. P.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione CNT, Roma, Italia; Tolomei, C.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione CNT, Roma, Italia; Salvi, S.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione CNT, Roma, Italia; Atzori, S.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione CNT, Roma, Italia; Antonioli, A.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione CNT, Roma, Italia; Trasatti, E.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione CNT, Roma, Italia; Novali, F.; Tele-Rilevamento Europa - T.R.E. srl; Serpelloni, E.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Bologna, Bologna, Italia; Candela, L.; Agenzia Spaziale Italiana, Unità Osservazione della Terra; Giuliani, R.; Dipartimento della Protezione Civile, Ufficio Rischio Sismico Abstract: On May 20th, 2012, an ML 5.9 earthquake (Table 1) occurred near the town of Finale Emilia, in the Central Po Plain, Northern Italy (Figure 1). The mainshock caused 7 casualties and the collapse of several historical buildings and industrial sheds. The earthquake sequence continued with diminishing aftershock magnitudes until May 29th, when an ML 5.8 earthquake occurred near the town of Mirandola, ~12 km WSW of the mainshock (Scognamiglio et al., 2012). This second mainshock started a new aftershock sequence in this area, and increased structural damage and collapses, causing 19 more casualties and increasing to 15.000 the number of evacuees. Shortly after the first mainshock, the Department of Civil Protection (DPC) activated the Italian Space Agency (ASI), which provided post-seismic SAR Interferometry data coverage with all 4 COSMO-SkyMed SAR satellites. Within the next two weeks, several SAR Interferometry (InSAR) image pairs were processed by the INGV-SIGRIS system (Salvi et al., 2012), to generate displacement maps and preliminary source models for the emergency management. These results included continuous GPS site displacement data, from private and public sources, located in and around the epicentral area. In this paper we present the results of the geodetic data modeling, identifying two main fault planes for the Emilia seismic sequence and computing the corresponding slip distributions. We discuss the implication of this seismic sequence on the activity of the frontal part of the Northern Apennine accretionary wedge by comparing the co-seismic data with the long term (geological) and present day (GPS) velocity fields. Mon, 31 Dec 2012 23:00:00 GMT http://hdl.handle.net/2122/8552 2012-12-31T23:00:00Z http://hdl.handle.net/2122/8548 Title: Spatial organization of foreshocks as a tool to forecast large earthquakes Authors: Lippiello, E.; Seconda Università di Napoli; Marzocchi, W.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma1, Roma, Italia; de Arcangelis, L.; Seconda Università di Napoli; Cataldo, G.; Seconda Università di Napoli Abstract: An increase in the number of smaller magnitude events, retrospectively named foreshocks, is often observed before large earthquakes. We show that the linear density probability of earthquakes occurring before and after small or intermediate mainshocks displays a symmetrical behavior, indicating that the size of the area fractured during the mainshock is encoded in the foreshock spatial organization. This observation can be used to discriminate spatial clustering due to foreshocks from the one induced by aftershocks and is implemented in an alarm-based model to forecast m . 6 earthquakes. A retrospective study of the last 19 years Southern California catalog shows that the daily occurrence probability presents isolated peaks closely located in time and space to the epicenters of five of the six m . 6 earthquakes. We find daily probabilities as high as 25% (in cells of size 0.04 3 0.04deg2), with significant probability gains with respect to standard models. Sat, 31 Dec 2011 23:00:00 GMT http://hdl.handle.net/2122/8548 2011-12-31T23:00:00Z http://hdl.handle.net/2122/8547 Title: Bayesian Forecast Evaluation and Ensemble Earthquake Forecasting Authors: Marzocchi, W.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma1, Roma, Italia; Zechar, J.; ETH Zurich; Jordan, T.; University of Southern California Abstract: The assessment of earthquake forecast models for practical purposes requires more than simply checking model consistency in a statistical framework. One also needs to understand how to construct the best model for specific forecasting applications. We describe a Bayesian approach to evaluating earthquake forecasting models, and we consider related procedures for constructing ensemble forecasts. We show how evaluations based on Bayes factors, which measure the relative skill among forecasts, can be complementary to common goodness-of-fit tests used to measure the absolute consistency of forecasts with data. To construct ensemble forecasts, we consider averages across a forecast set, weighted by either posterior probabilities or inverse log- likelihoods derived during prospective earthquake forecasting experiments. We account for model correlations by conditioning weights using the Garthwaite–Mubwandarikwa capped eigenvalue scheme. We apply these methods to the Regional Earthquake Like- lihood Models (RELM) five-year earthquake forecast experiment in California, and we discuss how this approach can be generalized to other ensemble forecasting applications. Specific applications of seismological importance include experiments being conducted within the Collaboratory for the Study of Earthquake Predictability (CSEP) and ensemble methods for operational earthquake forecasting. Sat, 31 Dec 2011 23:00:00 GMT http://hdl.handle.net/2122/8547 2011-12-31T23:00:00Z http://hdl.handle.net/2122/8337 Title: Comparison of characteristic and Gutenberg–Richter models for time-dependentM ≥ 7.9 earthquake probability in the Nankai-Tokai subduction zone, Japan Authors: Parsons, T.; U.S. Geological Survey, MS-999, 345 Middlefield Rd. Menlo Park, CA 94025, USA; Console, R.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma1, Roma, Italia; Falcone, G.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma2, Roma, Italia; Murru, M.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma1, Roma, Italia; Yamashina, K.; Earthquake Research Institute (ERI), University of Tokyo, Yayoi 1-1-1, Bunkyo-ku, Tokyo 113–0032, Japan Abstract: Earthquake forecasts are usually underinformed, and can be plagued by uncertainty in terms of the most appropriate model, and parameter values used in that model. In this paper, we explore the application of two different models to the same seismogenic area. The first is a renewal model based on the characteristic earthquake hypothesis that uses historical/palaeoseismic recurrence times, and fixed rupture geometries. The hazard rate is modified by the Coulomb static stress change caused by nearby earthquakes that occurred since the latest characteristic earthquake. The second model is a very simple earthquake simulator based on plate-motion, or fault-slip rates and adoption of a Gutenberg–Richter magnitude–frequency distribution. This information is commonly available even if historical and palaeoseismic recurrence data are lacking. The intention is to develop and assess a simulator that has a very limited parameter set that could be used to calculate earthquake rates in settings that are not as rich with observations of large-earthquake recurrence behaviour as the Nankai trough. We find that the use of convergence rate as a primary constraint allows the simulator to replicate much of the spatial distribution of observed segmented rupture rates along the Nankai, Tonankai and Tokai subduction zones. Although we note rate differences between the two forecast methods in the Tokai zone, we also see enough similarities between simulations and observations to suggest that very simple earthquake rupture simulations based on empirical data and fundamental earthquake laws could be useful forecast tools in information-poor settings. Fri, 31 Aug 2012 22:00:00 GMT http://hdl.handle.net/2122/8337 2012-08-31T22:00:00Z http://hdl.handle.net/2122/8336 Title: Predictability study on the aftershock sequence following the 2011 Tohoku-Oki, Japan, earthquake: first results Authors: Nanjo, K. Z.; Earthquake Research Institute, University of Tokyo, Tokyo, Japan.; Tsuruoka, H.; Earthquake Research Institute, University of Tokyo, Tokyo, Japan.; Yokoi, S.; Earthquake Research Institute, University of Tokyo, Tokyo, Japan.; Ogata, Y.; Institute of Statistical Mathematics, Tokyo, Japan; Falcone, G.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma2, Roma, Italia; Hirata, N.; Earthquake Research Institute, University of Tokyo, Tokyo, Japan.; Ishigaki, Y.; Japan Meteorological Agency, Tokyo, Japan; Jordan, T. H.; Southern California Earthquake Center, University of Southern California, Los Angeles, CA, USA; Kasahara, K.; Earthquake Research Institute, University of Tokyo, Tokyo, Japan.; Obara, K.; Earthquake Research Institute, University of Tokyo, Tokyo, Japan.; Schorlemmer, D.; Southern California Earthquake Center, University of Southern California, Los Angeles, CA, USA; Shiomi, K.; National Research Institute for Earth Science and Disaster Prevention, Ibaraki, Japan; Zhuang, J.; Institute of Statistical Mathematics, Tokyo, Japan Abstract: Although no deterministic and reliable earthquake precursor is known to date, we are steadily gaining insight into probabilistic forecasting that draws on space–time characteristics of earthquake clustering. Clustering-based models aiming to forecast earthquakes within the next 24 hours are under test in the global project ‘Collaboratory for the Study of Earthquake Predictability’ (CSEP). The 2011 March 11 magnitude 9.0 Tohoku-Oki earthquake in Japan provides a unique opportunity to test the existing 1-day CSEP models against its unprecedentedly active aftershock sequence. The original CSEP experiment performs tests after the catalogue is finalized to avoid bias due to poor data quality. However, this study differs from this tradition and uses the preliminary catalogue revised and updated by the Japan Meteorological Agency (JMA), which is often incomplete but is immediately available. This study is intended as a first step towards operability-oriented earthquake forecasting in Japan. Encouragingly, at least one model passed the test in most combinations of the target day and the testing method, although the models could not take account of the megaquake in advance and the catalogue used for forecast generation was incomplete. However, it can also be seen that all models have only limited forecasting power for the period immediately after the quake. Our conclusion does not change when the preliminary JMAcatalogue is replaced by the finalized one, implying that the models perform stably over the catalogue replacement and are applicable to operational earthquake forecasting. However, we emphasize the need of further research on model improvement to assure the reliability of forecasts for the days immediately after the main quake. Seismicity is expected to remain high in all parts of Japan over the coming years. Our results present a way to answer the urgent need to promote research on time-dependent earthquake predictability to prepare for subsequent large earthquakes in the near future in Japan. Wed, 31 Oct 2012 23:00:00 GMT http://hdl.handle.net/2122/8336 2012-10-31T23:00:00Z