Distance and Azimuthal Dependence of Ground‐Motion Variability for Unilateral Strike‐Slip Ruptures

Handle URI:
http://hdl.handle.net/10754/618213
Title:
Distance and Azimuthal Dependence of Ground‐Motion Variability for Unilateral Strike‐Slip Ruptures
Authors:
Vyas, Jagdish Chandra; Mai, Paul Martin ( 0000-0002-9744-4964 ) ; Galis, Martin ( 0000-0002-5375-7061 )
Abstract:
We investigate near‐field ground‐motion variability by computing the seismic wavefield for five kinematic unilateral‐rupture models of the 1992 Mw 7.3 Landers earthquake, eight simplified unilateral‐rupture models based on the Landers event, and a large Mw 7.8 ShakeOut scenario. We include the geometrical fault complexity and consider different 1D velocity–density profiles for the Landers simulations and a 3D heterogeneous Earth structure for the ShakeOut scenario. For the Landers earthquake, the computed waveforms are validated using strong‐motion recordings. We analyze the simulated ground‐motion data set in terms of distance and azimuth dependence of peak ground velocity (PGV). Our simulations reveal that intraevent ground‐motion variability Graphic is higher in close distances to the fault (<20  km) and decreases with increasing distance following a power law. This finding is in stark contrast to constant sigma‐values used in empirical ground‐motion prediction equations. The physical explanation of a large near‐field Graphic is the presence of strong directivity and rupture complexity. High values of Graphic occur in the rupture‐propagation direction, but small values occur in the direction perpendicular to it. We observe that the power‐law decay of Graphic is primarily controlled by slip heterogeneity. In addition, Graphic, as function of azimuth, is sensitive to variations in both rupture speed and slip heterogeneity. The azimuth dependence of the ground‐motion mean μln(PGV) is well described by a Cauchy–Lorentz function that provides a novel empirical quantification to model the spatial dependency of ground motion. Online Material: Figures of slip distributions, residuals to ground‐motion prediction equations (GMPEs), distance and azimuthal dependence, and directivity predictor of ground‐motion variability for different source models.
KAUST Department:
Physical Sciences and Engineering (PSE) Division
Citation:
Distance and Azimuthal Dependence of Ground‐Motion Variability for Unilateral Strike‐Slip Ruptures 2016, 106 (4):1584 Bulletin of the Seismological Society of America
Publisher:
Seismological Society of America (SSA)
Journal:
Bulletin of the Seismological Society of America
Issue Date:
21-Jun-2016
DOI:
10.1785/0120150298
Type:
Article
ISSN:
0037-1106; 1943-3573
Sponsors:
We thank Rob Graves for providing us with the source model of the ShakeOut scenario and Paul Spudich for sharing with us his MATLAB scripts to compute the directivity corrections. We thank Fabrice Cotton for his critical review that helped us to improve the manuscript. We also thank Kiran Kumar Thingbaijam for insightful discussions. The research presented in this article is supported by King Abdullah University of Science and Technology (KAUST) in Thuwal, Saudi Arabia. Earthquake rupture and ground‐motion simulations have been carried out using the KAUST Supercomputing Laboratory (KSL), and we acknowledge the support of the KSL staff.
Additional Links:
http://www.bssaonline.org/lookup/doi/10.1785/0120150298
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Articles

Full metadata record

DC FieldValue Language
dc.contributor.authorVyas, Jagdish Chandraen
dc.contributor.authorMai, Paul Martinen
dc.contributor.authorGalis, Martinen
dc.date.accessioned2016-08-10T13:08:35Z-
dc.date.available2016-08-10T13:08:35Z-
dc.date.issued2016-06-21-
dc.identifier.citationDistance and Azimuthal Dependence of Ground‐Motion Variability for Unilateral Strike‐Slip Ruptures 2016, 106 (4):1584 Bulletin of the Seismological Society of Americaen
dc.identifier.issn0037-1106-
dc.identifier.issn1943-3573-
dc.identifier.doi10.1785/0120150298-
dc.identifier.urihttp://hdl.handle.net/10754/618213-
dc.description.abstractWe investigate near‐field ground‐motion variability by computing the seismic wavefield for five kinematic unilateral‐rupture models of the 1992 Mw 7.3 Landers earthquake, eight simplified unilateral‐rupture models based on the Landers event, and a large Mw 7.8 ShakeOut scenario. We include the geometrical fault complexity and consider different 1D velocity–density profiles for the Landers simulations and a 3D heterogeneous Earth structure for the ShakeOut scenario. For the Landers earthquake, the computed waveforms are validated using strong‐motion recordings. We analyze the simulated ground‐motion data set in terms of distance and azimuth dependence of peak ground velocity (PGV). Our simulations reveal that intraevent ground‐motion variability Graphic is higher in close distances to the fault (<20  km) and decreases with increasing distance following a power law. This finding is in stark contrast to constant sigma‐values used in empirical ground‐motion prediction equations. The physical explanation of a large near‐field Graphic is the presence of strong directivity and rupture complexity. High values of Graphic occur in the rupture‐propagation direction, but small values occur in the direction perpendicular to it. We observe that the power‐law decay of Graphic is primarily controlled by slip heterogeneity. In addition, Graphic, as function of azimuth, is sensitive to variations in both rupture speed and slip heterogeneity. The azimuth dependence of the ground‐motion mean μln(PGV) is well described by a Cauchy–Lorentz function that provides a novel empirical quantification to model the spatial dependency of ground motion. Online Material: Figures of slip distributions, residuals to ground‐motion prediction equations (GMPEs), distance and azimuthal dependence, and directivity predictor of ground‐motion variability for different source models.en
dc.description.sponsorshipWe thank Rob Graves for providing us with the source model of the ShakeOut scenario and Paul Spudich for sharing with us his MATLAB scripts to compute the directivity corrections. We thank Fabrice Cotton for his critical review that helped us to improve the manuscript. We also thank Kiran Kumar Thingbaijam for insightful discussions. The research presented in this article is supported by King Abdullah University of Science and Technology (KAUST) in Thuwal, Saudi Arabia. Earthquake rupture and ground‐motion simulations have been carried out using the KAUST Supercomputing Laboratory (KSL), and we acknowledge the support of the KSL staff.en
dc.language.isoenen
dc.publisherSeismological Society of America (SSA)en
dc.relation.urlhttp://www.bssaonline.org/lookup/doi/10.1785/0120150298en
dc.rightsArchived with thanks to Bulletin of the Seismological Society of America. This copy is for distribution only by the authors of the article and their institutions in accordance with the Open Access Policy of the Seismological Society of America. For more information see the publications section of the SSA website at www.seismosoc.orgen
dc.titleDistance and Azimuthal Dependence of Ground‐Motion Variability for Unilateral Strike‐Slip Rupturesen
dc.typeArticleen
dc.contributor.departmentPhysical Sciences and Engineering (PSE) Divisionen
dc.identifier.journalBulletin of the Seismological Society of Americaen
dc.eprint.versionPublisher's Version/PDFen
dc.contributor.affiliationKing Abdullah University of Science and Technology (KAUST)en
kaust.authorVyas, Jagdish Chandraen
kaust.authorMai, Paul Martinen
kaust.authorGalis, Martinen
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