Seismic Evidence for a Lower-Crustal Detachment Beneath San Francisco Bay, California
1994; American Association for the Advancement of Science; Volume: 265; Issue: 5177 Linguagem: Inglês
10.1126/science.265.5177.1436
ISSN1095-9203
AutoresThomas M. Brocher, Jill McCarthy, Patrick E. Hart, W. Steven Holbrook, Kevin P. Furlong, T. V. McEvilly, J. A. Hole, S. L. Klemperer,
Tópico(s)Geological and Geochemical Analysis
ResumoResults 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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