Seismic evidence for a lower-crustal detachment beneath San Francisco Bay, California

T.M. Brocher; J. McCarthy; P. E. Hart; W.S. Holbrook; K.P. Furlong; T.V. McEvilly; J.A. Hole; S.L. Klemperer

doi:10.1126/science.265.5177.1436

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Seismic evidence for a lower-crustal detachment beneath San Francisco Bay, California

T.M. Brocher·J. McCarthy·P. E. Hart·W.S. Holbrook·K.P. Furlong·T.V. McEvilly·J.A. Hole·S.L. Klemperer

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Abstract

Results from the San Francisco Bay area seismic imaging experiment (BASIX) reveal the presence of a prominent lower crustal reflector at a depth of ∼15 kilometers beneath San Francisco and San Pablo bays. Velocity analyses indicate that this reflector marks the base of Franciscan assemblage rocks and the top of a mafic lower crust. Because this compositional contrast would imply a strong rheological contrast, this interface may correspond to a lower crustal detachment surface. If so, it may represent a subhorizontal segment of the North America and Pacific plate boundary proposed by earlier thermo-mechanical and geological models.

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Source-reported bounding extent: 37.41766415208987° to 37.84485905963611° latitude; -122.68862989936918° to -121.93467601391936° longitude. This indicates report coverage, not an exact sampling location. View area on OpenStreetMap.

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T.M. Brocher, J. McCarthy, P. E. Hart, W.S. Holbrook, K.P. Furlong, T.V. McEvilly, J.A. Hole, S.L. Klemperer. 1994. Seismic evidence for a lower-crustal detachment beneath San Francisco Bay, California. https://doi.org/10.1126/science.265.5177.1436

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