Modeling and Validation of a 3D Velocity Structure for the Santa Clara Valley, California, for Seismic-Wave Simulations

Hartzell, Stephen H.; Harmsen, Stephen C.; Williams, Robert A.; Carver, David; Frankel, Arthur; Choy, George L.; Liu, Pengcheng; Jachens, Robert C.; Brocher, Thomas M.; Wentworth, Carl M.

doi:10.1785/0120050243

Cited by 43 publications

(29 citation statements)

References 70 publications

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“…Regional differences in the sonic velocities and densities in these basins largely reflect variations in the lithology, depth of burial, grain size, and porosity, but are not necessarily the stratigraphic age of the deposits (Brocher, 2005c). Older Cenozoic sedimentary rocks contribute to the amplification of low frequency strong ground motions in these basins (e.g., Dolenc et al, 2005;Aagaard, 2006;Graves, 2006;Hartzell et al, 2006;Rodgers et al, 2006;Aagaard, Brocher, Dolenc, Dreger, Graves, Harmsen, Hartzell, Larsen, McCandless, et al, 2008;Rodgers et al, 2008). There are two primary datasets providing information on Vp versus depth for older Cenozoic sedimentary rocks.…”

Section: Older Cenozoic Sedimentary Rocksmentioning

confidence: 99%

Compressional and Shear-Wave Velocity versus Depth Relations for Common Rock Types in Northern California

Brocher

2008

Bulletin of the Seismological Society of America

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This article presents new empirical compressional and shear-wave velocity (Vp and Vs) versus depth relationships for the most common rock types in northern California. Vp versus depth relations were developed from borehole, laboratory, seismic refraction and tomography, and density measurements, and were converted to Vs versus depth relations using new empirical relations between Vp and Vs. The relations proposed here account for increasing overburden pressure but not for variations in other factors that can influence velocity over short distance scales, such as lithology, consolidation, induration, porosity, and stratigraphic age. Standard deviations of the misfits predicted by these relations thus provide a measure of the importance of the variability in Vp and Vs caused by these other factors. Because gabbros, greenstones, basalts, and other mafic rocks have a different Vp and Vs relationship than sedimentary and granitic rocks, the differences in Vs between these rock types at depths below 6 or 7 km are generally small. The new relations were used to derive the 2005 U.S. Geological Survey seismic velocity model for northern California employed in the broadband strong motion simulations of the 1989 Loma Prieta and 1906 San Francisco earthquakes; initial tests of the model indicate that the Vp model generally compares favorably to regional seismic tomography models but that the Vp and Vs values proposed for the Franciscan Complex may be about 5% too high.

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Section: Older Cenozoic Sedimentary Rocksmentioning

confidence: 99%

Compressional and Shear-Wave Velocity versus Depth Relations for Common Rock Types in Northern California

Brocher

2008

Bulletin of the Seismological Society of America

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“…The adopted numerical methods range finite differences (e.g. Olsen et al 1995, Moczo et al 2002, Graves & Wald 2004, Hartzell et al 2006, Harmsen et al 2008) or finite elements (e.g. Bao et al 1998, Aagaard et al 2001, Bielak et al 2005) to discontinuous Galerkin (e.g.…”

Section: Numerical Simulationsmentioning

confidence: 99%

Modelling basin effects on earthquake ground motion in the Santiago de Chile basin by a spectral element code

Pilz¹,

Parolai²,

Stupazzini³

et al. 2011

Geophysical Journal International

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S U M M A R YSimulations of strong ground motion within the Santiago de Chile Metropolitan area were carried out by means of 3-D deterministic wave propagation tool based on the spectral element method. The simulated events take into account the pronounced interface between the lowvelocity sedimentary basin and the bedrock as well as topography of the area. To verify our model we simulated a regional earthquake recorded by a dense network installed in the city of Santiago for recording aftershock activity after the 2010 February 27 Maule main shock. The results proof the alluvial basin amplification effects and show a strong dependence of spectral amplification in the basin on the local site conditions. Moreover, we studied the seismic response due to a hypothetical M w = 6.0 event occurring along the active San Ramón Fault, which is crossing the eastern edge of the city. The scenario earthquakes exhibit that an unfavourable interaction between fault rupture, radiation mechanism and complex geological and topographic conditions in the near-field region may give rise to large values of peak ground velocity in the basin. Finally, 3-D numerical predictions of ground motion are compared with the one computed according to ground motion prediction equations selected among the next generation attenuation relationships, in terms of ground motion peak values and spectral acceleration. The comparison underlines that the 3-D scenario simulations predict a significantly higher level of ground motion in the Santiago basin, especially over deep alluvial deposits. Moreover, also the location of the rupture nucleation largely influences the observed shaking pattern.

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“…The method has been successfully applied by a large number of authors to generate synthetic seismograms (e.g. Olsen and Archuleta 1996;Larsen et al 1997;Pitarka et al 2004;Hartzell et al 2006;Kagawa et al 2004;Grandin et al 2007a, b).…”

Section: Ground Motion Simulations and Earthquake Sourcementioning

confidence: 99%

Ground motion simulations of the SW Iberia margin: rupture directivity and earth structure effects

2011

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In this study, we focus on the region between Gorringe Bank and the Horseshoe Fault located in the SW Iberia margin, which is believed to be the site of the great 1755 earthquake. We model ground motions using an extended source located near the Horseshoe scarp to generate synthetic waveforms using a wave propagation code, based on the finite-difference method. We compare the simulated waveforms, for the Algarve Basin and the Lower Tagus Valley Basin (Portugal), using a 3-D velocity model down to the Moho discontinuity with a simple 1-D layered model. The radiated wave field is very sensitive to the velocity model and a small number of source parameters, in particular, the rupture directivity. The rupture directivity, the strike direction and the fault dimensions are critical to the azimuthal distribution of the maximum amplitude oscillations. We show that the use of a stratified 1-D model is inappropriate in SW Iberia, where sources are located in the oceanic domain and receivers in the continental domain. The crustal structure varies dramatically along the ray paths, with large-scale heterogeneities of low or high velocities. Moreover, combined with the geometric limitations inherent to the region, a strong tradeoff between several parameters is often observed; this is particularly critical when studying moderate magnitude earthquakes (M \ 6), which constitute the bulk of the seismic catalogue in SW Iberia.

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Modeling and Validation of a 3D Velocity Structure for the Santa Clara Valley, California, for Seismic-Wave Simulations

Cited by 43 publications

References 70 publications

Compressional and Shear-Wave Velocity versus Depth Relations for Common Rock Types in Northern California

Compressional and Shear-Wave Velocity versus Depth Relations for Common Rock Types in Northern California

Modelling basin effects on earthquake ground motion in the Santiago de Chile basin by a spectral element code

Ground motion simulations of the SW Iberia margin: rupture directivity and earth structure effects

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