Options
Herrero, André
Loading...
Preferred name
Herrero, André
Email
andre.herrero@ingv.it
Staff
staff
ORCID
Scopus Author ID
7102915258
44 results
Now showing 1 - 10 of 44
- PublicationOpen AccessReply to “Comment on ‘Influence of Focal Mechanism in Probabilistic Seismic Hazard Analysis’ by Vincenzo Convertito and André Herrero,” by F. O. Strasser, V. Montaldo, J. Douglas, and J. J. Bommer(2006-04)
; ; ;Convertito, V.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione OV, Napoli, Italia ;Herrero, A.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma1, Roma, Italia; We thank F. O. Strasser, V. Montaldo, J. Douglas, and J. J. Bommer for the interest they have shown in our article (Convertito and Herrero, 2004). Strasser et al. (2006) present a critical comment of our work arguing that the solution proposed by Bommer et al. (2003) is a better solution. Note that the authors are nearly the same in both article and comment, except for V. Montaldo. Because this brief article is a reply, we will focus on the arguments directly concerning our article. The main objection supported by Strasser et al. (2006) is that the method we proposed is not appropriate to "styleof-faulting" correction. We completely agree with this assertion because it is simply not the scope of our article. We speak about "focal mechanism" intended as radiation pattern and nothing else. This point is clearly stated in the introduction of Convertito and Herrero (2004): "in this article we consider that the focal mechanism influence is only expressed by radiation pattern changes. In particular we do not consider any tectonic influence, stress drop variation or dynamic effects." The style-of-faulting parameter, even if its identity is blurred (e.g., Bommer et al., 2003), is an empirical definition of a complex set of physical conditions including the tectonic regime, the medium behavior, rock mechanics, rupture dynamics, and so on. In our opinion, the style of faulting is simply too complex to be used directly in our approach. Because the scope of our article is to show how it is possible to insert inside the main equation of probabilistic seismic-hazard analysis (PSHA; e.g., Cornell, 1968), simple physical parameters of the seismic source, that is, how it is possible to integrate deterministic parameters inside a probabilistic approach, we have chosen a small target, limiting ourselves only to the radiation pattern. We believe that the same approach can be used to insert many other parameters of the seismic source inside PSHA by using only a theoretical approach such as the fault strike (which has already been shown by Convertito, 2004), the directivity and stress drop. The second important argumentation is that a method based on regression (i.e., Bommer et al., 2003) is better than the method we propose. Once again we agree with Strasser et al. (2006) and this is clearly stated in the conclusion of our article: "when an attenuation law, including a faulting style parameter, is available for a given region, the use of this attenuation law gives a more reliable estimate of the hazard than the one obtained using the corrective coefficient we propose in this article."199 131 - PublicationRestrictedFrom Seismic Monitoring to Tsunami Warning in the Mediterranean Sea(2021)
; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; The Italian Tsunami Alert Center based at the Istituto Nazionale di Geofisica e Vulcanologia (CAT-INGV) has been monitoring the Mediterranean seismicity in the past 8 yr to get fast and reliable information for seismically induced tsunami warnings. CAT-INGV is a tsunami service provider in charge of monitoring the seismicity of the Mediterranean Sea and of alerting Intergovernmental Oceanographic Commission (IOC)/UNESCO subscriber Member States and the Italian Department of Civil Protection of a potentially impending tsunami, in the framework of the Tsunami Warning and Mitigation System in the North-eastern Atlantic, the Mediterranean and connected seas (NEAMTWS). CAT-INGV started operating in 2013 and became operational in October 2016. Here, after describing the NEAMTWS in the framework of the global effort coordinated by IOC/UNESCO, we focus on the tsunami hazard in the Mediterranean Sea. We then describe CAT-INGV mandate, functioning, and operational procedures. Furthermore, the article discusses the lessons learned from past events occurring in the Mediterranean Sea, such as the Kos-Bodrum in 2017 (Mw 6.6) and the Samos-Izmir in 2020 (Mw 7.0) earthquakes, which generated moderately damaging tsunamis. Based on these lessons, we discuss some potential improvements for the CAT-INGV and the NEAMTWS, including better seismic and sea level instrumental cover- age. We emphasize the need for tsunami risk awareness raising, better preparation, and full implementation of the tsunami warning “last-mile” to foster the creation of a more integrated, interoperable, and sustainable risk reduction framework. If we aim to be better prepared for the next tsunami, these important challenges should be prioritized in the agenda of the IOC/UNESCO Member States and the European Commission.1406 2 - PublicationRestrictedPhysics‐Based Broadband Ground‐Motion Simulations for ProbableMw≥7.0 Earthquakes in the Marmara Sea Region (Turkey)(2017)
; ; ; ; ; ; ;; ; 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.995 9 - PublicationOpen AccessIntroduction of seismic source directivity on hazard map(2010-09-06)
; ; ; ; ;Spagnuolo, E.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma1, Roma, Italia ;Herrero, A.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma1, Roma, Italia ;Cultrera, G.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma1, Roma, Italia ;Spallarossa, D.;Università degli Studi di Genova, Dip.Te.Ris., Genova; ; ; The seismic hazard maps are mainly influenced by the uncertainty associated to the ground motion predictive equation (GMPE). This uncertainty represents the unexplained part of the ground motion and it is mostly related to the choice of the model’s variables. In fact the representation of the ground motion through the GMPEs is simple compared to the complexity of the physical process involved: if only the magnitude and distance are taken into account, GMPEs predicts isoseismals curves that are expected to be isotropic around the hypocenter or along the fault. Instead, the presence of a fault plane across which a process of failure in shear develops makes this general formulation reliable only on average. In fact this failure is responsible of an asymmetry in the seismic radiation known, since Ben-Menhaem (PhD1961), as directivity effect. While the general knowledge of the earthquakes is treated explicitly in the empirical prediction, specific trends like the directivity effects are hidden in the uncertainty sigma. A way to reduce the sigma is therefore to refine the seismic seismic source description inside the GMPEs (e.g. NGA project, Power et al, Earthquake Spectra, 2008). In this framework we propose a strategy to introduce the directivity in the GMPEs and to study its effect on uncertainties and on hazard maps. For this purpose, we have used two different directivity models acting on the GMPE as corrective factors: one proposed by Somerville et al. (Seis.Res.Lett.1997) and the other one proposed by Spudich and Chiou (Earthquake Spectra 2008).The first factor depends on geometrical parameters and comes from theoretical deduction. The second one includes many source parameters and it is a hybrid factor, which functional formulation is deduced from the theory, calibrated on synthetic simulations and scaled on data. The classic hazard equation is then adapted in order to increase the number of source parameters (i.e. adding one integral over the parametric space for each new variable involved) and taking into account the corrective factors for directivity (Spagnuolo, PhD2010). We present the comparisons of hazard maps depending on the directivity factor and on the probability density functions of the fault strike and of the rupture “laterality”.179 111 - PublicationRestrictedInfluence of focal mechanism in probabilistic seismic hazard analysis(2004-12)
; ; ;Convertito, V.; Universita` Federico II di Napoli ;Herrero, A.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma1, Roma, Italia; An extension of probabilistic seismic hazard analysis is proposed to introduce a priori information about seismic source parameters. In particular, faulting style is taken into account with a theoretical corrective coefficient applied to the attenuation law. The validity of this correction is assessed through a comparison with observed data, attenuation law predictions corrected and not corrected, and the results of attenuation laws containing faulting style parameters. The probabilistic nature of the analysis is maintained, introducing into the classical hazard formulation a 2D probability density function describing the most probable focal mechanisms associated with each seismic source zone. This new expression may also be used in the framework of deaggregation analysis. Thus, the design earthquake resulting from the deaggregation is characterized by a focal mechanism. An application to a site located in the Southern Apennines, Italy, is shown. The result of the analysis emphasizes the importance of strike-slip events in the seismic hazard context, compared with normal faulting seismic activity in this region.194 24 - PublicationOpen AccessSeismic monitoring using the telecom fiber network(2024-04)
; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ;; ; ; ; ; ; ; ; ;; ;Laser interferometry enables to remotely measure microscopical length changes of deployedtelecommunication cables originating from earthquakes. Long reach and compatibility with datatransmission make it attractive for the exploration of both remote regions and highly-populated areaswhere optical networks are pervasive. However, interpretation of its response still suffers from a limitednumber of available datasets. We systematically analyze 1.5 years of acquisitions on a land-basedtelecommunication cable in comparison to co-located seismometers, with successful detection ofevents in a broad magnitude range, including very weak ones. We determine relations between acable’s detection probability and the events magnitude and distance, introducing spectral analysis offiber data as a tool to investigate earthquake dynamics. Our results reveal that quantitative analysis ispossible, confirming applicability of this technique both for the global monitoring of our planet and thedaily seismicity monitoring of populated areas, in perspective exploitable for civilian protection77 1 - PublicationRestrictedImplementing the Effect of the Rupture Directivity on PSHA for the City of Istanbul, Turkey(2016)
; ; ; ; ; ; ; 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.675 7 - PublicationOpen AccessBayesian rupture imaging in a complex medium: The 29 May 2012 Emilia, Northern Italy, earthquake(2017-07-31)
; ; ; ; ; ; ;; ;; ;We develop a new approach to image earthquake rupture from strong motion data. We use a large data set of aftershock waveforms, interpolated over the seismic fault to obtain Green’s function approximations. Next we deploy a Bayesian inversion method to characterize the slip distribution, the rupture velocity, the slip duration, and their uncertainties induced by errors in the Green’s functions. The method is applied to the 29 May 2012 Mw 6 Emilia earthquake, which ruptured a fault buried below the Po Plain sediments (Northern Italy). Despite the particularly complex wave propagation, the near-field strong motion observations are well reproduced with 15 rupture parameters. The rupture and slip velocities were notably slow (~0.5 Vs and <0.5 m/s, respectively), implying that the fault was difficult to break. This method opens some perspectives for earthquake rupture studies in areas where numerical simulations suffer from imprecise knowledge of the velocity structure.214 27 - PublicationRestrictedVariability of kinematic source parameters and its implication on the choice of the design scenario(2010)
; ; ; ; ; ; ;Cultrera, G.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma1, Roma, Italia ;Cirella, A.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma1, Roma, Italia ;Spagnuolo, E.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma1, Roma, Italia ;Herrero, A.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma1, Roma, Italia ;Tinti, E.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma1, Roma, Italia ;Pacor, F.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Milano-Pavia, Milano, Italia; ; ; ; ; Near-fault seismic recordings for recent earthquakes (Chi Chi earthquake, 1999, and Parkfield earthquake, 2004) show the high spatial heterogeneity of ground motion. This variability is controlled by fault geometry, rupture complexity, and also by wave propagation and site effects. Nowadays, the number of available records in the near-source region is still not enough to infer a robust parameterization of the ground motion and to retrieve multiparametric predictive equations valid at close distances from the fault. The use of a synthetic approach may help to overcome this limitation and to study the strong ground motion variability. In this article we focus on ground-motion dependence on different earthquakes breaking the same fault, as it has been rarely recorded by instruments. We model seismic scenarios from different rupture models of a fault similar to the 1980 Irpinia, Italy, earthquake source (Mw 6.9). A discrete wavenumber/finite element technique is used to compute fullwave displacement and velocity time series in the low-frequency band (up to 2 Hz). We investigate the variability of the ground motion as a function of different source parameters (rupture velocity, slip distribution, nucleation point, and source time function), whose values depend on the state of knowledge of the physical model driving the process. The probability density functions of the simulated ground-motion parameters, such as displacement response spectrum and peak ground velocity, are used to identify particular scenarios that match specific engineering requests.232 19 - PublicationOpen AccessDetails of the rupture Kinematics and mechanism of the 1980 Irpinai earthquake: new results and remaining questions(1993)
; ; ; ; ;Bernard, P.; Institute de Physique du Globe de Paris, France ;Zollo, A.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione OV, Napoli, Italia ;Trifu, C.I.; Center of Earth Physics and Seismology, Bucharest, Romania ;Herrero, A.; Institute de Physique du Globe de Paris, France; ; ; 188 182