Rupture parameters of dynamic source models compatible with NGA-West2 GMPEs

Mapping Intimacies ◽

10.5194/egusphere-egu2020-16610 ◽

2020 ◽

Author(s):

Frantisek Gallovic ◽

Lubica Valentova

Keyword(s):

Ground Motions ◽

Source Parameters ◽

Strong Motion ◽

Seismic Hazard Assessment ◽

Response Spectra ◽

Maximum Magnitude ◽

Source Inversion ◽

Dynamic Rupture ◽

Heterogeneous Distribution ◽

Dynamic Source

Dynamic source inversions of individual earthquakes provide constraints on stress and frictional parameters, which are inherent to the studied event. However, general characteristics of both kinematic and dynamic rupture parameters are not well known, especially in terms of their variability. Here we constrain them by creating and analyzing a synthetic event database of dynamic rupture models that generate waveforms compatible with strong ground motions in a statistical sense.We employ a framework that is similar to the Bayesian dynamic source inversion by Gallovi&#269; et al. (2019). Instead of waveforms of a single event, the data are represented by Ground Motion Prediction Equations (GMPEs), namely NGA-West2&#160; (Boore et al., 2014). The Markov chain Monte Carlo technique produces samples of the dynamic source parameters with heterogeneous distribution on a fault. For all simulations, we assume a vertical 36x20km strike-slip fault, which limits our maximum magnitude to Mw<7. For dynamic rupture calculations, we employ upgraded finite-difference code FD3D_TSN (Premus et al., 2020) with linear slip-weakening friction law. Seismograms are calculated on a regular grid of phantom stations assuming a 1D velocity model using precalculated full wavefield Green's functions. The procedure results in a database with those dynamic rupture models that generate ground motions compatible with the GMPEs (acceleration response spectra in period band 0.5-5s) in terms of both median and variability.The events exhibit various magnitudes and degrees of complexity (e.g. one or more asperities). We inspect seismologically determinable parameters, such as duration, moment rate spectrum, stress drop, size of the ruptured area, and energy budget, including their variabilities.&#160; Comparison with empirically derived values and scaling relations suggests that the events are compatible with real earthquakes (Brune, 1970, Kanamori and Brodsky, 2004). Moreover, we investigate the stress and frictional parameters in terms of their scaling, power spectral densities, and possible correlations. The inferred statistical properties of the dynamic source parameters can be used for physics-based strong-motion modeling in seismic hazard assessment.

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Dynamic source inversion of the 2014 Mw6 South Napa, California, earthquake

10.5194/egusphere-egu2020-18422 ◽

2020 ◽

Author(s):

Jan Premus ◽

Frantisek Gallovic

Keyword(s):

Monte Carlo ◽

Strong Motion ◽

Inversion Method ◽

Source Inversion ◽

Dynamic Rupture ◽

Dynamic Simulations ◽

Simulation Code ◽

Strong Motion Data ◽

Motion Data ◽

Dynamic Source

Dynamic rupture modeling coupled with strong motion data fitting (dynamic source inversion) offers an insight into the rupture physics, constraining and enriching information gained from standard kinematic slip inversions. We utilize the Bayesian Monte Carlo dynamic source inversion method introduced recently by Gallovi&#269; et al. (2019), which, in addition to finding a best-fitting model, allows assessing uncertainties of the inferred parameters by sampling the posterior probability density function. The Monte Carlo approach requires running a large number (millions) of dynamic simulations due to the nonlinearity of the inverse problem. It is achieved by using GPU accelerated dynamic rupture simulation code FD3D_TSN (Premus et al., submitted) as a forward solver. We apply the inversion to the 2014 Mw6 South Napa, California, earthquake, employing strong motion data (up to 0.5 Hz) from the 10 closest stations. As an output, we obtain samples of the spatial distributions of dynamic parameters (prestress and parameters of the slip-weakening friction law). Regarding the rupture geometry, we consider two, presently ambiguous, fault planes (Pollitz et al., 2019), showing considerable differences in fitting seismograms in very close vicinity of the fault. We investigate properties of the rupture, especially in the region close to the free surface, and the viability of the model samples to explain the observed data in a broader frequency range (up to 5Hz).

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FD3D_TSN: A Fast and Simple Code for Dynamic Rupture Simulations with GPU Acceleration

Seismological Research Letters ◽

10.1785/0220190374 ◽

2020 ◽

Vol 91 (5) ◽

pp. 2881-2889 ◽

Cited By ~ 1

Author(s):

Jan Premus ◽

František Gallovič ◽

Ladislav Hanyk ◽

Alice-Agnes Gabriel

Keyword(s):

Seismic Hazard Assessment ◽

Gpu Acceleration ◽

Staggered Grid ◽

Source Inversion ◽

Dynamic Rupture ◽

Motion Modeling ◽

Graphic Processing Units ◽

Source Imaging ◽

Core Solution ◽

Dynamic Source

Abstract We introduce FD3D_TSN—an open-source Fortran code for 3D dynamic earthquake rupture modeling based on the staggered grid fourth-order finite-difference method employing a regular cubical spatial discretization. Slip-weakening and fast-velocity-weakening rate-and-state fault friction laws are combined with vertical planar fault geometry, orthogonal to a planar free surface. FD3D_TSN demonstrates good agreement with other methods in a range of benchmark exercises of the Southern California Earthquake Center and U.S. Geological Survey dynamic rupture code verification project. Efficient graphic processing units (GPU) acceleration using the OpenACC framework yields a factor of 10 speed-up in terms of time to solution compared to a single-core solution for current hardware (Intel i9-9900K and Nvidia RTX 2070). The software is fast and easy-to-use and suitable explicitly for data-driven applications requiring a large number of forward simulations such as dynamic source inversion or probabilistic ground-motion modeling. The code is freely available for the scientific community and may be incorporated in physics-based earthquake source imaging and seismic hazard assessment, or for teaching purposes.

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Comparison of local kinematic rupture joint inversion approaches for tsunami early warning: Examples of the 2017-2020 Mw > 6.3 East Aegean earthquakes

10.5194/egusphere-egu21-5221 ◽

2021 ◽

Author(s):

Malte Metz ◽

Marius Isken ◽

Rongjiang Wang ◽

Torsten Dahm ◽

Haluk Özener ◽

...

Keyword(s):

Early Warning ◽

Joint Inversion ◽

Moment Tensor ◽

Strong Motion ◽

Aegean Sea ◽

High Rate ◽

Source Inversion ◽

Dynamic Rupture ◽

Centroid Moment Tensor ◽

Tsunami Early Warning

The fast inversion of reliable centroid moment tensor and kinematic rupture parameters of earthquakes occurring near coastal margins is a key for the assessment of the tsunamigenic potential and early tsunami warning (TEW). In recent years, more and more multi-channel seismic and geodetic online station networks have been built-up to improve the TEW, for instance the GNSS and strong motion networks in Italy, Greece, and Turkey, additionally to the broadband seismological monitoring. Inclusion of such data for the fast kinematic source inversion can improve the resolution and robustness of its&#8217; solutions. However, methods have to be further developed and tested to fully exploit the potential of such rich joint dataset.In this frame, we compare and test two in-house developed, kinematic / dynamic rupture inversion methods which are based on completely different approaches. The IDS (Iterative Deconvolution and Stacking, Zhang et al., 2014) combines an iterative seismic network inversion with back projection techniques to retrieve subfault source time functions. The pseudo dynamic rupture model (Dahm et al., in review) links the rupture front propagation estimate based on the Eikonal equation with the dislocation derived from a boundary element method to model dislocation snapshots. We used the latter in both a fast rupture estimate and a fully probabilistic source inversion.We use some Mw > 6.3 earthquakes that occurred in the coastal range of the Aegean Sea as an example for comparison: the Mw 6.3 Lesbos earthquake (12 June 2017), the Mw 6.6 Bodrum earthquake (20 July 2017), and the recent Mw 7.0 earthquake which occurred at Samos on 30 October 2020. The latter earthquake and the resulting tsunami caused fatalities and severe damage at the shorelines of Samos and around the city of Izmir, Turkey. The fast estimates are based on only little data and/or prior information obtained from the regional seismicity catalogue and available active fault information. The large number of seismic (broadband, strong motion) and geodetic (high-rate GNSS) stations in local and regional distance from the earthquake with good azimuthal coverage jointly inverted with InSAR data allows for robust inversion results. These, and other solutions, are used as a reference for the comparison of our fast source estimates. Preliminary results of the slip distribution and the source time function are in good agreement with modelling results from other authors.We present our insights into the kinematics of the chosen earthquakes investigated by means of joint inversions. Finally, the accuracy of our first fast source estimates, which could be of potential use in tsunami early warning, will be discussed.

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Dynamic Rupture and Ground Motion Modeling of the 2016 M6.2 Amatrice and M6.5 Norcia, Central Italy, Earthquakes Constrained by Bayesian Dynamic Source Inversion

10.5194/egusphere-egu2020-20584 ◽

2020 ◽

Author(s):

Taufiq Taufiqurrahman ◽

Alice-Agnes Gabriel ◽

Frantisek Gallovic ◽

Lubica Valentova

Keyword(s):

Ground Motion ◽

Dynamic Models ◽

Central Italy ◽

Foot Wall ◽

Source Inversion ◽

Dynamic Rupture ◽

Highly Efficient ◽

Starting Point ◽

Dynamic Source ◽

Strong Ground

The complex evolution of earthquake rupture during the 2016 Central Italy sequence and the uniquely dense seismological observations provide an opportunity to better understand the processes controlling earthquake dynamics, strong ground motion, and earthquake interaction.&#160;We here use fault initial stress and friction conditions constrained by a novel Bayesian dynamic source inversion as a starting point for high-resolution dynamic rupture scenarios. The best-fitting forward models are chosen out of ~106 highly efficient simulations restricted to a simple planar dipping fault. Such constrained, highly heterogeneous dynamic models fit strong motion data well. Utilizing the open-source SeisSol software (www.seissol.org), we then take into account non-planar (e.g., listric) fault geometries, inelastic off-fault damage rheology, free surface effects and topography which cannot be accounted for in the highly efficient dynamic source inversion. SeisSol is based on the discontinuous Galerkin method on unstructured tetrahedral meshes optimized for modern supercomputers.&#160;We investigate the effects of including the realistic modeling ingredients on rupture dynamics and strong ground motions up to 5 Hz. Synthetic PGV mapping reveals that specifically fault listricity decreases ground motion amplitudes by&#160; ~50 percent in the extreme near field on the foot-wall. On the hanging-wall shaking is increased by ~150 percent as a consequence of wave-focusing effects within 10 km away from the fault. Dynamic modeling thus suggests that geometrical fault complexity is important for seismic hazard assessment adjacent to dipping faults but difficult to identify by kinematic source inversions.

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Spatial Variability of Source and Attenuation Characteristics in Large Ground-Motion Datasets

10.5194/egusphere-egu2020-5187 ◽

2020 ◽

Author(s):

Sreeram Reddy Kotha ◽

Graeme Weatherill ◽

Dino Bindi ◽

Fabrice Cotton

Keyword(s):

Spatial Variability ◽

Ground Motion ◽

Ground Motions ◽

Low Frequency ◽

Strong Motion ◽

Response Spectra ◽

Large Datasets ◽

Earthquake Scenarios ◽

Crustal Earthquakes ◽

Geographical Regions

Ground-Motion Models (GMMs) characterize the random distributions of ground-motions for a combination of earthquake source, wave travel-path, and the effected site&#8217;s geological properties. Typically, GMMs are regressed over a compendium of strong ground-motion recordings collected from several earthquakes recorded at multiple sites scattered across a variety of geographical regions. The necessity of compiling such large datasets is to expand the range of magnitude, distance, and site-types; in order to regress a GMM capable of predicting realistic ground-motions for rare earthquake scenarios, e.g. large magnitudes at short distances from a reference rock site. The European Strong-Motion (ESM) dataset is one such compendium of observations from a few hundred shallow crustal earthquakes recorded at a several hundred seismic stations in Europe and Middle-East.We developed new GMMs from the ESM dataset, capable of predicting both the response spectra and Fourier spectra in a broadband of periods and frequencies, respectively. However, given the clear tectonic and geological diversity of the data, possible regional and site-specific differences in observed ground-motions needed to be quantified; whilst also considering the possible contamination of data from outliers. Quantified regional differences indicate that high-frequency ground-motions attenuate faster with distance in Italy compared to the rest of Europe, as well as systematically weaker ground-motions from central Italian earthquakes. In addition, residual analyses evidence anisotropic attenuation of low frequency ground-motions, imitating the pattern of shear-wave energy radiation. With increasing spatial variability of ground-motion data, the GMM prediction variability apparently increases. Hence, robust mixed-effects regressions and residual analyses are employed to relax the ergodic assumption.Large datasets, such as the ESM, NGA-West2, and from KiK-Net, provide ample opportunity to identify and evaluate the previously hypothesized event-to-event, region-to-region, and site-to-site differences in ground-motions. With the appropriate statistical methods, these variabilities can be quantified and applied in seismic hazard and risk predictions. We intend to present the new GMMs: their development, performance and applicability, prospective improvements and research needs.

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Seismic Hazard Assessment in the Southeastern United States

Earthquake Spectra ◽

10.1193/1.1585806 ◽

1995 ◽

Vol 11 (1) ◽

pp. 129-160 ◽

Cited By ~ 1

Author(s):

Paul C. Rizzo ◽

N. R. Vaidya ◽

E. Bazan ◽

C. F. Heberling

Keyword(s):

North American ◽

Peak Ground Acceleration ◽

Ground Motions ◽

Near Field ◽

Southeastern United States ◽

Seismic Hazard Assessment ◽

Response Spectra ◽

Seismic Hazards ◽

Far Field ◽

Ground Acceleration

Comparisons of response spectra from near and far-field records to those estimated by attenuation functions commonly used in evaluating seismic hazards show that these functions provide reasonable results for near-field western North American sites. However, they estimate relatively small motions for far-field eastern North American sites, which is contrary to the empirical evidence of the 1886 Charleston and 1988 Saguenay Earthquakes. Using the 1988 Saguenay records scaled for magnitude, and several western North American records scaled to account for the slower attenuation in the east, we have developed deterministic median and 84th percentile, 5 percent damped response spectra to represent ground motions from a recurrence of the 1886 Charleston Earthquake at a distance between 85 to 120 km. The resulting 84th percentile spectrum has a shape similar to, but is less severe than, the USNRC Regulatory Guide 1.60 5 percent damped spectrum tied to a peak ground acceleration of 0.2g.

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Improved finite-source inversion through joint measurements of rotational and translational ground motions: A theoretical study

10.5194/se-2016-67 ◽

2016 ◽

Author(s):

Michael Reinwald ◽

Moritz Bernauer ◽

Heiner Igel ◽

Stefanie Donner

Keyword(s):

Inverse Problem ◽

Ground Motions ◽

Source Parameters ◽

Normal Fault ◽

Seismic Source ◽

Vertical Gradient ◽

Vertical Displacement ◽

Source Inversion ◽

Additional Information ◽

Finite Source

Abstract. With the prospects of seismic equipment being able to measure rotational ground motions in a wide frequency and amplitude range in the near future we engage in the question how this type of ground motion observation can be used to solve the seismic inverse problem. In this paper, we focus on the question, whether finite source inversion can benefit from additional observations of rotational motion. Keeping the overall number of traces constant, we compare observations from a surface seismic network with 44 3-component translational sensors (classic seismometers) with those obtained with 22 6-component sensors (with additional 3-component rotational motions). Synthetic seismograms are calculated for known finite-source properties. The corresponding inverse problem is posed in a probabilistic way using the Shannon information content as measure how the observations constrain the seismic source properties. We minimize the influence of the source receiver geometry around the fault by statistically analyzing six-component (three velocity and three rotation rate) inversions with a random distribution of receivers. The results show that with the 6-C subnetworks the source properties are not only equally well recovered (even that would be benefitial because of the substantially reduced logistics installing half the sensors) but statistically some source properties are almost always better resolved. We assume that this can be attributed to the fact that the (in particular vertical) gradient information is contained in the additional motion components. We compare these effects for strike-slip and normal-faulting type sources and confirm that the increase in inversion quality for kinematic source parameters is even higher for the normal fault. This indicates that the inversion benefits from the additional information provided by the horizontal rotation rates, i.e. information about the vertical displacement gradient.

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Imaging the rupture process of recent earthquakes using backprojection of local high frequency records

10.5194/egusphere-egu2020-13283 ◽

2020 ◽

Author(s):

Ioannis Fountoulakis ◽

Christos Evangelidis ◽

Olga-Joan Ktenidou

Keyword(s):

High Frequency ◽

A Priori ◽

Strong Motion ◽

Seismic Hazard Assessment ◽

Seismic Source ◽

Site Effect ◽

Source Inversion ◽

Waveform Data ◽

Novel Approach ◽

Spatio Temporal

The seismic source spatio-temporal rupture processes of events in Japan, Greece and Turkey are imaged by backprojection of strong-motion waveforms. Normalized high-frequency (> 2Hz) S-waveforms from recordings on dense strong-motion networks are used to scan a predefined 3D source volume over time.&#160;Backprojection is an alternative novel approach to image the spatio-temporal earthquake rupture. The method was first applied for large earthquakes at teleseismic distances, but is nowadays also used at local distances and over higher frequencies. The greatest advantage of the method is that processing is done without any a-priori constraints on the geometry, or size of the source. Thus, the spatio-temporal imaging of the rupture is feasible at higher frequencies (> 1Hz) than conventional source inversion studies, even when the examined fault geometry is complex. This high-frequency energy emitted during an earthquake is of great importance in seismic hazard assessment for certain critical infrastructures. The actual challenge in using high-frequency local recordings is to distinguish the local site effects from the true earthquake source content - otherwise, mapping the former incorrectly onto the latter limits the resolvability of the method. It is not straightforward to remove the site effect component or even to distinguish good reference stations from amid hard-soil and rock sites. In this study, the advantages and limitations of the method are explored using waveform data from well-recorded events in Japan (Kumamoto Mw7.1, 2016), Turkey (Marmara Mw6.4, 2019) and Greece (Antikythera Mw6.1, 2019). For each event and seismic array the resolution limits of the applied method are explored by performing various synthetic tests.

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A New State‐of‐the‐Art Platform for Probabilistic and Deterministic Seismic Hazard Assessment

Seismological Research Letters ◽

10.1785/0220190025 ◽

2019 ◽

Vol 90 (6) ◽

pp. 2262-2275 ◽

Cited By ~ 5

Author(s):

Gabriel Candia ◽

Jorge Macedo ◽

Miguel A. Jaimes ◽

Carolina Magna‐Verdugo

Keyword(s):

Seismic Hazard ◽

Ground Motion ◽

Hazard Assessment ◽

State Of The Art ◽

Ground Motions ◽

Tectonic Setting ◽

Source Parameters ◽

Seismic Hazard Assessment ◽

Hazard Evaluation ◽

Benchmark Solutions

ABSTRACT A new computational platform for seismic hazard assessment is presented. The platform, named SeismicHazard, allows characterizing the intensity, uncertainty, and likelihood of ground motions from subduction‐zone (shallow interface and intraslab) and crustal‐zone earthquakes, considering site‐specific as well as regional‐based assessments. The platform is developed as an object‐oriented MATLAB graphical user interface, and it features several state‐of‐the‐art capabilities for probabilistic and deterministic (scenario‐based) seismic hazard assessment. The platform integrates the latest developments in performance‐based earthquake engineering for seismic hazard assessment, including seismic zonation models, ground‐motion models (GMMs), ground‐motion correlation structures, and the estimation of design spectra (uniform hazard spectra, classical conditional mean spectrum (CMS) for a unique tectonic setting). In addition to these standard capabilities, the platform supports advanced features, not commonly found in existing seismic hazard codes, such as (a) computation of source parameters from earthquake catalogs, (b) vector‐probabilistic seismic hazard assessment, (c) hazard evaluation based on conditional GMMs and user‐defined GMMs, (d) uncertainty treatment in the median ground motions through continuous GMM distributions, (e) regional shaking fields, and (f) estimation of CMS considering multiple GMMs and multiple tectonic settings. The results from the platform have been validated against accepted and well‐documented benchmark solutions.

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