Using twelve years of USGS refraction lines to calibrate the Brocher and others (1997) 3D velocity model of the Bay Area

Boatwright, John; Blair, Luke; Catchings, R. D.; Goldman, M.; Perosi, Fábio André; Steedman, C. E.

doi:10.3133/ofr20041282

Cited by 17 publications

(26 citation statements)

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“…VSP and sonic log data provide measurements of Vp for the Franciscan Complex to depths up to 2.7 km (Majer et al, 1988;Newhouse et al, 2004;Brocher, 2005c). Laboratory measurements of Franciscan Complex rocks (Stewart and Peselnick, 1978), laboratory measurements for graywackes (Christensen and Mooney, 1995;Brocher and Christensen, 2001), and tomography velocities sample Franciscan Complex rocks at various depths up to 20 km (Beaudoin et al, 1996;Parsons and Zoback, 1997;Henstock and Levander, 2000;Hole et al, 2000;Boatwright et al, 2004;Catchings et al, 2004;Hauksson et al, 2004;Hardebeck et al, 2007).…”

Section: Franciscan Complex (Metagraywacke)mentioning

confidence: 98%

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

Brocher

2008

Bulletin of the Seismological Society of America

103

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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: Franciscan Complex (Metagraywacke)mentioning

confidence: 98%

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

Brocher

2008

Bulletin of the Seismological Society of America

103

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“…For the San Francisco Bay Area (SFBA), we use Version 08.3.0 of a 3D Bay Area velocity model developed by Boatwright et al (2004; http://earthquake.usgs.gov/research/ structure/3dgeologic/). Similar to the SCEC model, this 3-D velocity model is based on a structural and geological model of the region, which is converted to V p and then to V s .…”

Section: Basin Models In Northern Californiamentioning

confidence: 99%

NGA-West2 Site Database

Seyhan

Stewart

Ancheta³

et al. 2014

Earthquake Spectra

100

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The NGA-West2 site database (SDB) contains information on site condition and instrument housing for 4,147 strong-motion stations with recordings in the project flatfile. The stations are from active tectonic regions, mainly in California, Japan, Taiwan, China, and the Mediterranean area. The principal site parameter is the time-averaged shear wave velocity in the upper 30 m (V S30 ), which we characterize using measurements where available (2,013 stations) and proxy-based relationships otherwise. We also provide basin depths from published models for 2,761 sites mostly in California and Japan. We improved the documentation and consistency of site descriptors used as proxies for V S30 estimation (surface geology, ground slope, and geotechnical or geomorphic categories) and analyzed proxy performance relative to V S30 values from measurements. We present protocols for V S30 estimation from proxies that emphasize methods minimizing bias and dispersion relative to data. For each site, we provide the preferred V S30 and its dispersion.

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“…The obtained velocity structure is comparable with additional velocity images derived from SFBR refraction experiments. Profiles AA′ and BB′ of Figure 8c coincide with portions of profiles AA′ and BB′ of Boatwright et al [2004]. Along profile AA′ the two velocity images both exhibit a strong low‐velocity volume from profile distance 0 to 20 km at depth ≲8 km, which envelopes the Loma Prieta rupture zone (see also Figure 18b).…”

Section: Discussionmentioning

confidence: 67%

“…This sense of velocity contrast at depth is seen in the y = 32.5 km, y = 42.5 km, and y = 52.5 km profiles in Figure 8a, and also in profile CC′ of Figure 8c. Profile CC′ has been taken to coincide with a portion of profile CC′ of Boatwright et al [2004], which contains velocity images derived from travel time tomography of several SFBR refraction experiments. The two sets of velocity profiles agree with the sense of velocity contrast across the SAF at both shallow (<5 km) and greater depth.…”

Section: Discussionmentioning

confidence: 99%

Waveform tomography of crustal structure in the south San Francisco Bay region

Pollitz

Fletcher

2005

J. Geophys. Res.

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We utilize a scattering‐based seismic tomography technique to constrain crustal structure around the southern San Francisco Bay region (SFBR). This technique is based on coupled traveling wave scattering theory, which has usually been applied to the interpretation of surface waves in large regional‐scale studies. Using fully three‐dimensional kernels, this technique is here applied to observed P, S, and surface waves of intermediate period (3–4 s dominant period) observed following eight selected regional events. We use a total of 73 seismograms recorded by a U.S. Geological Survey short‐period seismic array in the western Santa Clara Valley, the Berkeley Digital Seismic Network, and the Northern California Seismic Network. Modifications of observed waveforms due to scattering from crustal structure include (positive or negative) amplification, delay, and generation of coda waves. The derived crustal structure explains many of the observed signals which cannot be explained with a simple layered structure. There is sufficient sensitivity to both deep and shallow crustal structure that even with the few sources employed in the present study, we obtain shallow velocity structure which is reasonably consistent with previous P wave tomography results. We find a depth‐dependent lateral velocity contrast across the San Andreas fault (SAF), with higher velocities southwest of the SAF in the shallow crust and higher velocities northeast of the SAF in the midcrust. The method does not have the resolution to identify very slow sediment velocities in the upper approximately 3 km since the tomographic models are smooth at a vertical scale of about 5 km.

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Using twelve years of USGS refraction lines to calibrate the Brocher and others (1997) 3D velocity model of the Bay Area

Cited by 17 publications

References 0 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

NGA-West2 Site Database

Waveform tomography of crustal structure in the south San Francisco Bay region

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