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Institute of Geophysic, ETH Zurich, Switzerland
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- PublicationOpen AccessSTOCHASTIC AND FULL-WAVEFIELD FINITE-FAULT GROUND-MOTION SIMULATIONS OF THE M7.1, MESSINA 1908 EARTHQUAKE (Southern Italy)(2008-12)
; ; ; ; ; ;Zonno, G.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Milano-Pavia, Milano, Italia ;Musacchio, G.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Milano-Pavia, Milano, Italia ;Basili, R.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma1, Roma, Italia ;Imperatori, W.; Institute of Geophysics-ETH, Zurich ;Mai, P. M.; Institute of Geophysics-ETH, Zurich; ; ; ; In the framework of an ongoing Italian national research project we are studying the Messina 1908 earthquake, the first to be recorded adequately by seismological and geodetic instrumentation that allowed subsequent quantitative investigations of its source properties. We use a high-frequency stochastic finite-fault modeling (Motazedian and Atkinson, 2005) to simulate the ground-shaking for a number of different source models (Basili et al. 2008), either constrained from past source studies of this event or simulated. Although inherently kinematic, our approach accounts for the physics of the source using a procedure to generate physically consistent earthquake-rupture models (Guatteri et al., 2004). Considering the width of the seismogenic zone and appropriate source-scaling relation, we generate heterogeneous slip models that obey to the source complexity of past earthquakes (Mai and Beroza, 2002). By also constraining the point of rupture initiation based on empirical findings and energy-balance arguments (Mai et al., 2005), we generate a suite of earthquake source models to compute far-field ground-shaking. The Housner parameter from the stochastic high-frequency simulations is than compared with the felt intensity (MCS scale). The developed procedure is a necessary tool to take into account the influence of directivity effects in simulating ground shaking scenarios using realistic slip distribution on the fault. Furthermore, we carry out full-wavefield ground-motion calculations (at frequencies f < 3 Hz) to compare those low-frequency simulations with (a) the stochastic simulations and (b) appropriate ground-motion prediction equations. The combined approach helps to examine the validation range of the two methods (distinguishing the influence of the near-field and far-field motions on the shaking level), and may serve as a basis to develop a hybrid technique which combines the two methods for generating fully broadband synthetic seismograms.188 397 - PublicationOpen AccessMaximum Observable Shaking (MOS) maps of Italy (Final report)(2010-06-10)
; ; ; ; ; ; ;Zonno, G.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Milano-Pavia, Milano, Italia ;Musacchio, G.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Milano-Pavia, Milano, Italia ;Meroni, F.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Milano-Pavia, Milano, Italia ;Basili, R.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma1, Roma, Italia ;Imperatori, W.; Institute of Geophysic, ETH Zurich, Switzerland ;Mai, P. M.; King Abdullah University of Science & Technology (KAUST), Division of Physical Sciences & Engineering (Thuwal, Saudi Arabia); ; ; ; ; We investigate wave motion through numerical simulations that take into account primarily the ground acceleration in response to a given earthquake rupture that radiates seismic waves. The shaking that potential sources might cause is plotted on maps that provide a general overview of the hazard over a large area, and that can be used as the starting point for further detailed investigations. Here, we establish a procedure to compute ground motion that spans the entire frequency range of engineering interest (i.e., broad-band), and we derive the maximum shaking that is caused by expected earthquakes throughout Italy (i.e. the maximum observable shaking; MOS). Our approaches merge updated knowledge of the Italian regional tectonic setting and of source-zone definitions (Valensise and Pantosti, 2001; Basili et al., 2008) and scenario-like calculations of the expected MOS in any given area.189 207 - PublicationOpen AccessDelimitation of Near-fields boundaries (Final Report)(2010-06-10)
; ; ; ; ; ; ;Zonno, G.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Milano-Pavia, Milano, Italia ;Musacchio, G.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Milano-Pavia, Milano, Italia ;Meroni, F.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Milano-Pavia, Milano, Italia ;Basili, R.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma1, Roma, Italia ;Imperatori, W.; Institute of Geophysic, ETH Zurich, Switzerland ;Mai, P. M.; King Abdullah University of Science & Technology (KAUST), Division of Physical Sciences & Engineering (Thuwal, Saudi Arabia); ; ; ; ; We examine possibilities to delineate the boundaries between near-field and far-field radiation of seismic waves. Near-field (NF), intermediate-field (IF) and far-field (FF) terms represent different properties of the seismic wave-field: the near-source motions are sensitive to the spatio-temporal details of the rupture process, while far-field terms tend to carry the overall signature of the rupture. Due to the longer propagation path of far-field waves through complex Earth structure, their waveform properties also depend more strongly on media properties (scattering; intrinsic attenuation), than it is the case for the NF-wavefield.199 152 - PublicationOpen AccessUR 3.13 - MAXIMUM OBSERVABLE SHAKING (MOS) MAPS OF ITALY(2009-10)
; ; ; ; ; ; ;Zonno, G.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Milano-Pavia, Milano, Italia ;Musacchio, G.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Milano-Pavia, Milano, Italia ;Meroni, F.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Milano-Pavia, Milano, Italia ;Basili, R.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma1, Roma, Italia ;Imperatori, W.; Institute of Geophysics (ETH), Zurich, Switzerland ;Mai, P.M.; Institute of Geophysics (ETH), Zurich, Switzerland; ; ; ; ; The main goal of UR 3.13 is to establish a work flow for a multi-layer map that includes the seismicity of Italy in terms of Maximum Observable Shaking (MOS), and the near-field/far-field boundaries (NF/FF) with respect to the major seismogenic faults mapped within the DISS database. Here we will discuss only the procedure to derive the MOS-map of Italy. Our approach merges updated knowledge on the Italian regional tectonic setting and on the Source Zone (SZ) definition and broadband scenario-like calculation of expected maximum shaking on a given area. For a given SZ, broadband ground shaking is computed for a rupture model derived from a Maximum Credible Earthquake (MCE) and its associated Typical Fault (TF). Amplitude spectra for deterministic Low Frequency and stochastic High Frequency waveforms are reconciled at intermediate frequency, where their domain of validity overlaps, to derive broadband synthetics and compute the associated shaking. As the MCE and TF float along the SZ, broadband ground motion is computed at each point surrounding the given fault and the maximum among observable shaking according to that scenario is plotted on the MOS map. So far the procedure was entirely successfully tested on the Macro Region MR4 (central-northern Apennine), while more detailed analysis is done on the MCE and TF suggested for the Colfiorito earthquake. Here our broadband ground motion scenario shows, besides a complex pattern of variation, a southwestern area of high PGA values, at about 20 km distance from the fault, likely associated to with the properties of the spatio-temporal complexity of the rupture process. For the purpose of the project a complete new map of SZ and MCE is under compilation, grouping seismogenic sources according to Mw and faulting mechanisms. This goal can be achieved most efficiently by targeted numerical simulations that cover the parameter range of interest (in terms of magnitude and distance etc) and consider a large suite earthquake rupture scenarios.168 173 - PublicationRestrictedHybrid Broadband Seismograms for Seismic Shaking Scenarios: An Application to the Po Plain Sedimentary Basin (Northern Italy)(2020)
; ; ; ; ; ; ; ; ; ; ; The densely populated Po Plain, a very deep sedi- mentary basin in northern Italy, is prone to heavy shaking during earthquakes. Seismic hazard assessment must account for local variation in wave amplification. Standard ground motion prediction equations may fail to picture the complexity of strong lateral gradients in seismic response, due to sharp structural heterogeneity. For this reason, there is an increasing demand for full waveform predictions for engineering applications. Here, we present an implementation of a hybrid broadband simulation based on the method of Mai et al. (Bull Seismol Soc Am 100(6):3338–3339, 2010), to obtain complete broadband seismograms of 0.1–10 Hz. With this method, low frequency (<1 Hz) and high frequency (1–10 Hz) seismograms are simulated separately using a deter- ministic and a stochastic method, respectively. We apply the method to four events recorded within the Po basin, with magnitude ranging from Mw = 4.4 to Mw = 5.6. The low frequency (LF) simulation is performed using SPECFEM3D on a few test sub- surface velocity models. The three-dimensional velocity model MAMBo (Molinari et al. in Bull Seismol Soc Am 105(2A):753–764, 2015)—consisting of a detailed structural description of the basin, based on extensive active-source data, embedded within a regional 3D crustal model—provided the best results for broadband simulations that most closely corresponded with the observations. It performed better than an ambient noise tomography model with more accurate S-wave velocities but less well defined layer topographies, emphasizing the importance of first order velocity discontinuities. The high frequency (HF) seis- mograms are simulated using the multiple scattering approach of Zeng et al. (J Geophys Res Solid Earth 96(B1):607–619, 1991). The scattering coefficients are obtained by performing a non linear inversion for each station to find best fitting synthetic envelopes. HF energy is then combined at 1 Hz to match the amplitude and phase spectra of the LF signal. We are able to simulate full waveforms throughout the Po Plain, of which shaking duration matches observed data for stations located in the basin. Shaking amplitudes are generally overestimated in the low frequency simulation by the MAMBo velocity model. Updating the MAMBo velocity model with more accurate S-wave velocity information of the ambient noise tomography model should improve the fit in future simulations.769 3