ABSTRACT The purpose of this study is to use ground-motion simulations to investigate ways in which source and path effects for large-magnitude earthquakes can be represented in nonergodic ground-motion models (GMMs). To achieve this, we designed a ground-motion study in the San Francisco Bay Area that includes earthquakes with a broad range of magnitudes distributed uniformly on a fault plane, and sites covering a large range of rupture distances and azimuths. After running a large suite of kinematic simulations (magnitude 4–7), we then develop a nonergodic GMM with the simulated data. We find that trends in the within-site residuals are affected significantly by the earthquake radiation pattern, rupture directivity, and slip patterns. Next, we modify an existing rupture directivity model to fit and remove the observed radiation pattern and rupture directivity from the residuals. We also minimize the contributions of slip patterns by averaging the within-site residuals among multiple source realizations. Finally, after removing the source effects from the within-site residuals, we compare the path effects computed with different magnitude groups using two approaches. The first approach only considers the small events that have the same shortest path to a site as the large events, whereas the second approach considers all small events on the fault plane. The results indicate that it is difficult to satisfactorily approximate the path effects of large events with those of small events using either approach, at least in the case of simulations.

Abstract This work assesses the ability of the Graves–Pitarka simulation approach to reproduce observed ground motions for 12 California and Baja California earthquakes. A total of 240 realizations are computed for each earthquake and compared with recorded strong motions from near-fault sites. In addition to spatial variability in slip, each realization samples from discrete combinations of average rupture speed, rise time, and down-dip fault width. Ground motions for each realization of a given earthquake are compared to the observations using a pseudo-spectral acceleration goodness-of-fit (GoF) metric. Parameters for the lowest misfit cases are then tabulated to develop relations for estimating median values and ranges for future applications. The results are generally consistent with published scaling relations for estimating rupture dimensions as a function of magnitude. Additionally, I find the average rise time scales as $${2.3\times \alpha }_{T}\times {10}^{-9}{\times M}_{o}^{1/3}$$ 2.3 × α T × 10 - 9 × M o 1 / 3 (M o is seismic moment in dyne-cm) and average rupture speed as $$(0.765 \pm 0.075)\times {\alpha }_{T}^{-1}\times {V}_{s}$$ ( 0.765 ± 0.075 ) × α T - 1 × V s (V s is local shear wave velocity), where a T is a mechanism adjustment ranging from a value of 1.0 for pure strike-slip to 0.9 for pure reverse-slip cases. There are cases where slightly different combinations of parameters produce equally good fits to the observations, demonstrating the non-uniqueness of using a single GoF metric in this approach. Nonetheless, the results reinforce the importance of adequately sampling ranges of rupture parameters when performing validations, as well as when simulating ground motions for future events. Graphical Abstract

Coherent patterns and large variations in ground shaking amplification were observed in the Los Angeles basin during the 2019 M7.1 Ridgecrest earthquake. In particular, 3 s to 6 s responses showed variations due to shallow basin geological structure that have implications for the response to large earthquakes of mid-rises, high-rises, long-span bridges, and fuel storage tanks, even if epicentral distances are several hundred kilometers. The Ridgecrest strong-motion data were recorded by seismic stations from the spatially dense Community Seismic Network, the Southern California Seismic Network, and the California Strong Motion Instrumentation Program. The mainshock observations are compared at the same locations with ground motion simulations to examine the regions that experienced the largest shaking, and to investigate the geological sources of large-amplitude shaking. The simulations were computed for the two most commonly used regional community seismic velocity models, CVM-S4.26.M01 ('CVM-S') and CVM-H 15.1.0 ('CVM-H'). Both observations and simulations are used in dynamic analysis with a finite-element model of an existing high-rise with 6-s fundamental horizontal periods, located in downtown Los Angeles. The geographical variation in maximum story drift, story-level shear force, and story-level moment values suggest that the excitation of a hypothetical high-rise located in an area characterized by the largest 6-s PSA values could be significantly larger than in a downtown Los Angeles location. Ground motion simulations using the CVM-H velocity model more closely predict the long-period site amplifications in greater Los Angeles, particularly in the south-central San Fernando Valley, than simulations using CVM-S.

ABSTRACTThe main objective of this study is to develop physics-based constraints on the spatiotemporal variation of the slip-rate function using a simplified dynamic rupture model. First, we performed dynamic rupture modeling of the 2019 Mw 7.1 Ridgecrest, California, earthquake, to analyze the effects of depth-dependent stress and material friction on slip rate. Then, we used our modeling results to guide refinements to the slip-rate function that were implemented in the Graves–Pitarka kinematic rupture generation technique. The dynamic ruptures were computed on a surface-rupturing, planar strike-slip fault that includes a weak (negative to low-stress-drop) zone in the upper 4 km of the crust. Below the weak zone, we placed high-stress-drop patches designed to mirror the large-slip areas seen in various rupture model inversions of the event. The locations of the high-stress-drop patches and the hypocenter were varied in multiple realizations to investigate how changing the dynamic conditions affected the resulting rupture kinematics, in particular, the slip rate. From these simulations, we observed a systematic change in the shape of the slip-rate function from Kostrov type below the weak zone to a predominantly symmetric shape within the weak zone, along with a depth-dependent reduction of peak slip rate. We generalized these shallow rupture features into a depth-dependent parametric variation of the slip-rate function and implemented it in the Graves–Pitarka kinematic rupture model generator. The performance of the updated kinematic approach was then verified in 0–4 Hz simulations of the Mw 7.1 Ridgecrest earthquake, which showed that incorporating the depth-dependent variation in the shape of the slip-rate function improves the fit to the observed near-fault ground motions in the 0.5–3 s period range.

Over the past decade, there is growing consensus that physics-based simulations can be utilized in engineering applications. However, for the simulations to be accepted, they need to be calibrated and validated. This study presents the results of ground motion simulation calibration and validation using earthquakes that occurred in the Upper Rhine Graben with a modified version of the Graves-Pitarka (GP) hybrid ground-motion simulation methodology implemented on the Southern California Earthquake Center Broadband Platform, which uses an improved high-frequency computation. To calibrate the HF simulation, we take advantage of the growth of seismological data (including weak motions) in the region and the ability to evaluate critical seismic parameters such as anelastic attenuation, stress drop, and site effects through spectral decomposition methods (separate site-source-propagation from the datasets). Hence in the simulation, the adopted anelastic attenuation and stress parameter are defined based on the spectral decomposition results. The additional modification of the standard GP method is the incorporation of compressional wave in the HF motion.Results are compared with observations and simulations from the unmodified GP approach; we also use a range of ground motion intensity measures as summary statistics. We found that in general, the modification in the HF part (e.g., incorporation of compressional waves) was necessary to improve the fit with observations. Our findings also validate the fact that parameters from the spectral decomposition are giving well-calibrated time-histories (in terms of frequency and amplitude) when used as input parameters of the broadband simulations. The findings in this study support the incorporation of scenario-based ground motion simulations for use in the characterization of seismic hazard and other engineering applications. For simulation of future earthquakes, instead of using event-specific stress-drops, we use the average stress-drops taken from the distribution of the stress drops derived from spectral decomposition.

We present a synoptic analysis of the ground motions from the 11 March 1933 Mw 6.4 Long Beach, California, earthquake, the largest known earthquake within the central Los Angeles Basin region. Our inferred shaking intensity pattern supports the association of the earthquake with the Newport-Inglewood fault; it further illuminates the concentration of severe damage in the town of Compton, where accounts suggest vertical ground motions exceeding 1 g . We use a broadband simulation approach to develop a rupture scenario for this earthquake, informed by the damage distribution. The predicted shaking for a 25-km-long fault matches the intensity distribution, with an indication that non-linear site response on soft sediments in some near-field regions was stronger than predicted using a simple model to account for non-linearity. Our results suggest that the concentration of damage near Compton can be explained by a combination of local site amplification, source-controlled directivity, and three-dimensional basin effects whereby energy was channeled towards the deepest part of the Los Angeles Basin.

The objective of our study is the improvement of shallow rupture characterization in kinematic rupture models used in strong ground motion simulations. Based on geological investigations, earthquake stress drop, depth-variation of seismicity, as well as recorded near-fault ground motion, there is clear evidence for depth variation of frictional properties of crustal materials. The material ductility in the weak zone (upper 3-5 km of the crust) and the transition from ductile state to brittle state in the upper seismogenic zone, determine how the fracture energy is consumed by the earthquake rupture, and how generated seismic energy is distributed in space and time. Using plausible stress models for crustal ruptures, we performed dynamic rupture simulations on vertical strike slip faults that break the free surface. We used a 3D staggered-grid finite-difference method (Pitarka and Dalguer, 2009) and regional 1D velocity model. The stress drop as a function of slip was modeled using a linear slip weakening frictional law that reflects the depth and lateral variations of frictional properties of crustal materials. Through dynamic rupture modeling we were able to extract kinematic rupture characteristics, such as changes in the shape of slip rate functions, rupture velocity, and peak slip rate across the weak zone, and in the slip asperity areas. These results were then used to refine our existing rupture generating model (Graves and Pitarka, 2016) for crustal earthquakes. The modifications to the rupture generator code include changes to the shape of slip-rate function at shallow depths, rise time variation with depth and stronger correlation with slip at shallow depths. The effects of the new characterization of shallow rupture kinematics on simulated ground motion was thoroughly investigated in broad-band (0-10Hz) simulations of the M7.1 2019 Ridgecrest California earthquake. The ground motion time histories were computed using the hybrid method of Graves and Pitarka (2010. In our simulations we considered several slip distributions, including two that were obtained by inverting recorded velocity and displacement ground motion, respectively. Finally, through comparisons with recorded data, we analyzed the sensitivity of computed near-fault broad-band ground motion characteristics, including amplitude of ground motion velocity pulse, peak acceleration, and response spectra, to shallow slip characterization and location of strong motion generation areas for each rupture model. The proposed modifications to kinematic rupture models of crustal earthquakes provide improved simulation of broadband strong ground motion and seismic hazard assessment. This work was performed under the auspices of the U.S. Department of Energy by Lawrence Livermore National Laboratory under Contract DE-AC52-07NA27344

We analyzed a kinematic earthquake rupture generator that combines the randomized spatial field approach of Graves and Pitarka (Bull Seismol Soc Am 106:2136–2153, 2016 ) (GP2016) with the multiple asperity characterization approach of Irikura and Miyake (Pure Appl Geophys 168:85–104, 2011 ) (IM2011, also known as Irikura recipe). The rupture generator uses a multi-scale hybrid approach that incorporates distinct features of both original approaches, such as small-scale stochastic rupture variability and depth-dependent scaling of rupture speed and slip rate, inherited from GP2016, and specification of discrete high slip rupture patches, inherited from IM2011. The performance of the proposed method is examined in simulations of broadband ground motion from the 2016 Kumamoto, Japan earthquake, as well as comparisons with ground motion prediction equations (GMPEs). We generated rupture models with multi-scale heterogeneity, including a hybrid one in which the slip is a combination of high- slip patches and stochastic small scale variations. We find that the ground motions simulated with these rupture models match the general characteristics of the recorded near-fault motion equally well, over a broad frequency range (0–10 Hz). Additionally, the simulated ground motion is in good agreement with the predictions from Ground Motion Prediction Equations (GMPEs). Nonetheless, due to sensitivity of the ground motion to the local fault rupture characteristics, the performance among the models at near-fault sites is slightly different, with the hybrid model producing a somewhat better fit to the recorded ground velocity waveforms. Sensitivity tests of simulated near-fault ground motion to variations in the prescribed kinematic rupture parameters show that average rupture speeds higher than the default value in GP2016 (average rupture speed = 80% of local shear wave speed), as well as slip rate durations shorter than the default value in GP2016 (rise time coefficient = 1.6), generate ground motions that are higher than the recorded ones at periods longer than 1 s. We found that these two parameters also affect the along strike and updip rupture directivity effects, as illustrated in comparisons with the Kumamoto observations.

Editorial| February 28, 2018 Integrate Urban‐Scale Seismic Hazard Analyses with the U.S. National Seismic Hazard Model M. P. Moschetti; M. P. Moschetti aU.S. Geological Survey, P.O. Box 25046, MS 966, Denver, Colorado 80225 U.S.A., mmoschetti@usgs.govfU.S. Geological Survey Working Group on Urban Seismic Hazard Maps. Search for other works by this author on: GSW Google Scholar N. Luco; N. Luco aU.S. Geological Survey, P.O. Box 25046, MS 966, Denver, Colorado 80225 U.S.A., mmoschetti@usgs.gov Search for other works by this author on: GSW Google Scholar A. D. Frankel; A. D. Frankel bUniversity of Washington, Department of Earth and Space Sciences, ATG‐228, Seattle, Washington 98195 U.S.A. Search for other works by this author on: GSW Google Scholar M. D. Petersen; M. D. Petersen aU.S. Geological Survey, P.O. Box 25046, MS 966, Denver, Colorado 80225 U.S.A., mmoschetti@usgs.gov Search for other works by this author on: GSW Google Scholar B. T. Aagaard; B. T. Aagaard cU.S. Geological Survey, 345 Middlefield Road, MS 977, Menlo Park, California 94025‐3591 U.S.A. Search for other works by this author on: GSW Google Scholar A. S. Baltay; A. S. Baltay cU.S. Geological Survey, 345 Middlefield Road, MS 977, Menlo Park, California 94025‐3591 U.S.A. Search for other works by this author on: GSW Google Scholar M. L. Blanpied; M. L. Blanpied dU.S. Geological Survey, 12201 Sunrise Valley Drive, MS 905, Reston, Virginia 20192 U.S.A. Search for other works by this author on: GSW Google Scholar O. S. Boyd; O. S. Boyd aU.S. Geological Survey, P.O. Box 25046, MS 966, Denver, Colorado 80225 U.S.A., mmoschetti@usgs.gov Search for other works by this author on: GSW Google Scholar R. W. Briggs; R. W. Briggs aU.S. Geological Survey, P.O. Box 25046, MS 966, Denver, Colorado 80225 U.S.A., mmoschetti@usgs.gov Search for other works by this author on: GSW Google Scholar R. D. Gold; R. D. Gold aU.S. Geological Survey, P.O. Box 25046, MS 966, Denver, Colorado 80225 U.S.A., mmoschetti@usgs.gov Search for other works by this author on: GSW Google Scholar R. W. Graves; R. W. Graves eU.S. Geological Survey, 525 South Wilson Avenue, Pasadena, California 91106 U.S.A. Search for other works by this author on: GSW Google Scholar S. H. Hartzell; S. H. Hartzell aU.S. Geological Survey, P.O. Box 25046, MS 966, Denver, Colorado 80225 U.S.A., mmoschetti@usgs.gov Search for other works by this author on: GSW Google Scholar S. Rezaeian; S. Rezaeian aU.S. Geological Survey, P.O. Box 25046, MS 966, Denver, Colorado 80225 U.S.A., mmoschetti@usgs.gov Search for other works by this author on: GSW Google Scholar W. J. Stephenson; W. J. Stephenson aU.S. Geological Survey, P.O. Box 25046, MS 966, Denver, Colorado 80225 U.S.A., mmoschetti@usgs.gov Search for other works by this author on: GSW Google Scholar D. J. Wald; D. J. Wald aU.S. Geological Survey, P.O. Box 25046, MS 966, Denver, Colorado 80225 U.S.A., mmoschetti@usgs.gov Search for other works by this author on: GSW Google Scholar R. A. Williams; R. A. Williams aU.S. Geological Survey, P.O. Box 25046, MS 966, Denver, Colorado 80225 U.S.A., mmoschetti@usgs.gov Search for other works by this author on: GSW Google Scholar K. B. Withers K. B. Withers aU.S. Geological Survey, P.O. Box 25046, MS 966, Denver, Colorado 80225 U.S.A., mmoschetti@usgs.gov Search for other works by this author on: GSW Google Scholar Seismological Research Letters (2018) 89 (3): 967–970. https://doi.org/10.1785/0220170261 Article history first online: 23 Apr 2018 Cite View This Citation Add to Citation Manager Share Icon Share Facebook Twitter LinkedIn MailTo Tools Icon Tools Get Permissions Search Site Citation M. P. Moschetti, N. Luco, A. D. Frankel, M. D. Petersen, B. T. Aagaard, A. S. Baltay, M. L. Blanpied, O. S. Boyd, R. W. Briggs, R. D. Gold, R. W. Graves, S. H. Hartzell, S. Rezaeian, W. J. Stephenson, D. J. Wald, R. A. Williams, K. B. Withers; Integrate Urban‐Scale Seismic Hazard Analyses with the U.S. National Seismic Hazard Model. Seismological Research Letters 2018;; 89 (3): 967–970. doi: https://doi.org/10.1785/0220170261 Download citation file: Ris (Zotero) Refmanager EasyBib Bookends Mendeley Papers EndNote RefWorks BibTex toolbar search Search Dropdown Menu toolbar search search input Search input auto suggest filter your search All ContentBy SocietySeismological Research Letters Search Advanced Search For more than 20 yrs, damage patterns and instrumental recordings have highlighted the influence of the local 3D geologic structure on earthquake ground motions (e.g., M 6.7 Northridge, California, Gao et al., 1996; M 6.9 Kobe, Japan, Kawase, 1996; M 6.8 Nisqually, Washington, Frankel, Carver, and Williams, 2002). Although this and other local‐scale features are critical to improving seismic hazard forecasts, historically they have not been explicitly incorporated into the U.S. National Seismic Hazard Model (NSHM, national model and maps), primarily because the necessary basin maps and methodologies were not available at the national scale. Instead,... You do not have access to this content, please speak to your institutional administrator if you feel you should have access.

We investigate the performance of two kinematic rupture generation techniques proposed by Graves and Pitarka (GP0216), and Irikura and Miyake (IM2011), by simulating broad-band strong ground motion recorded during the 2016, Kumamoto, Japan earthquake. Here we also propose a new kinematic rupture model generation techniques that combines the GP2016 model with the multiple asperity rupture model IM2011, known as the Irikura recipe. The proposed model incorporates distinct features of both original rupture models, including small-scale stochastic rupture variability, and depth dependent slip rate and rise time, inherited from the GP2016, and desired near-fault rupture directivity effects produced by the deterministic representation of large asperities, inherited from the IM2011

The purpose of this report is to provide a set of ground motion models (GMMs) to be considered by the U.S. Geological Survey (USGS) for their National Seismic Hazard Maps (NSHMs) for the Central and Eastern U.S. (CEUS). These interim GMMs are adjusted and modified from a set of preliminary models developed as part of the Next Generation Attenuation for Central and Eastern North-America (CENA) project (NGA-East). The NGA-East objective was to develop a new ground-motion characterization (GMC) model for the CENA region. The GMC model consists of a set of GMMs for median and standard deviation of ground motions and their associated weights in the logic-tree for use in probabilistic seismic hazard analysis (PSHA). NGA-East is a large multidisciplinary project coordinated by the Pacific Earthquake Engineering Research Center (PEER), at the University of California, Berkeley. The project has two components: (1) a set of scientific research tasks, and (2) a model-building component following the framework of the “Seismic Senior Hazard Analysis Committee (SSHAC) Level 3” [Budnitz et al. 1997; NRC 2012]. Component (2) is built on the scientific results of component (1) of the NGA-East Project. This report does not document the final NGA-East model under (2), but instead presents interim GMMs for use in the U.S. Geological Survey (USGS) National Seismic Hazard Maps. Under component (1) of NGA-East, several scientific issues were addressed, including: (a) development of a new database of empirical data recorded in CENA; (b) development of a regionalized ground-motion map for CENA, (c) definition of the reference site condition; (d) simulations of ground motions based on different methodologies, (e) development of numerous GMMs for CENA, and (f) the development of the current report. The scientific tasks of NGA- East were all documented as a series of PEER reports. This report documents the GMMs recommended by the authors for consideration by the USGS for their NSHM. The report documents the key elements involved in the development of the proposed GMMs and summarizes the median and aleatory models for ground motions along with their recommended weights. The models presented here build on the work from the authors and aim to globally represent the epistemic uncertainty in ground motions for CENA. The NGA-East models for the USGS NSHMs includes a set of 13 GMMs defined for 25 ground-motion intensity measures, applicable to CENA in the moment magnitude range of 4.0 to 8.2 and covering distances up to 1500 km. Standard deviation models are also provided for general PSHA applications (ergodic standard deviation). Adjustment factors are provided for hazard computations involving the Gulf Coast region.

We analyzed the performance of the Irikura and Miyake (Pure and Applied Geophysics 168(2011):85–104, 2011) (IM2011) asperity-based kinematic rupture model generator, as implemented in the hybrid broadband ground motion simulation methodology of Graves and Pitarka (Bulletin of the Seismological Society of America 100(5A):2095–2123, 2010), for simulating ground motion from crustal earthquakes of intermediate size. The primary objective of our study is to investigate the transportability of IM2011 into the framework used by the Southern California Earthquake Center broadband simulation platform. In our analysis, we performed broadband (0–20 Hz) ground motion simulations for a suite of M6.7 crustal scenario earthquakes in a hard rock seismic velocity structure using rupture models produced with both IM2011 and the rupture generation method of Graves and Pitarka (Bulletin of the Seismological Society of America, 2016) (GP2016). The level of simulated ground motions for the two approaches compare favorably with median estimates obtained from the 2014 Next Generation Attenuation-West2 Project (NGA-West2) ground motion prediction equations (GMPEs) over the frequency band 0.1–10 Hz and for distances out to 22 km from the fault. We also found that, compared to GP2016, IM2011 generates ground motion with larger variability, particularly at near-fault distances (<12 km) and at long periods (>1 s). For this specific scenario, the largest systematic difference in ground motion level for the two approaches occurs in the period band 1–3 s where the IM2011 motions are about 20–30% lower than those for GP2016. We found that increasing the rupture speed by 20% on the asperities in IM2011 produced ground motions in the 1–3 s bandwidth that are in much closer agreement with the GMPE medians and similar to those obtained with GP2016. The potential implications of this modification for other rupture mechanisms and magnitudes are not yet fully understood, and this topic is the subject of ongoing study. We concluded that IM2011 rupture generator performs well in ground motion simulations using Graves and Pitarka hybrid method. Therefore, we recommend it to be considered for inclusion into the framework used by the Southern California Earthquake Center broadband simulation platform.