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

Thomas M. Brocher, Jill McCarthy, Patrick E. Hart, W. Steven Holbrook, Kevin P. Furlong, Thomas V. McEvilly, John A. Hole, Simon 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 thermomechanical and geological models.

Original languageEnglish (US)
Pages (from-to)1436-1439
Number of pages4
JournalScience
Volume265
Issue number5177
DOIs
StatePublished - Sep 2 1994

All Science Journal Classification (ASJC) codes

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    Brocher, T. M., McCarthy, J., Hart, P. E., Holbrook, W. S., Furlong, K. P., McEvilly, T. V., Hole, J. A., & Klemperer, S. L. (1994). Seismic evidence for a lower-crustal detachment beneath San Francisco Bay, California. Science, 265(5177), 1436-1439. https://doi.org/10.1126/science.265.5177.1436