Finite-frequency traveltime tomography of San Francisco Bay region crustal velocity structure

F. F. Pollitz

doi:10.1111/j.1365-246x.2007.03532.x

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Finite-frequency traveltime tomography of San Francisco Bay region crustal velocity structure

F. F. Pollitz

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Abstract

Seismic velocity structure of the San Francisco Bay region crust is derived using measurements of finite-frequency traveltimes. A total of 57 801 relative traveltimes are measured by cross-correlation over the frequency range 0.5–1.5 Hz. From these are derived 4862 ‘summary’ traveltimes, which are used to derive 3-D P -wave velocity structure over a 341 × 140 km 2 area from the surface to 25 km depth. The seismic tomography is based on sensitivity kernels calculated on a spherically symmetric reference model. Robust elements of the derived P -wave velocity structure are: a pronounced velocity contrast across the San Andreas fault in the south Bay region (west side faster); a moderate velocity contrast across the Hayward fault (west side faster); moderately low velocity crust around the Quien Sabe volcanic field and the Sacramento River delta; very low velocity crust around Lake Berryessa. These features are generally explicable with surface rock types being extrapolated to depth ∼10 km in the upper crust. Generally high mid-lower crust velocity and high inferred Poisson's ratio suggest a mafic lower crust.

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Geophysical Journal International Article

Source-reported bounding extent: 36.92551991847962° to 38.695260367185796° latitude; -123.44690589033075° to -121.2505826039804° longitude. This indicates report coverage, not an exact sampling location. View area on OpenStreetMap.

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F. F. Pollitz. 2007. Finite-frequency traveltime tomography of San Francisco Bay region crustal velocity structure. https://doi.org/10.1111/j.1365-246x.2007.03532.x

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