title: Seismic evidence for a lower-crustal detachment beneath san francisco bay, california.
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 approximately 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.
authors.forename: T M
authors.initials: TM
authors.lastname: Brocher
authors.forename: J
authors.initials: J
authors.lastname: McCarthy
authors.forename: P E
authors.initials: PE
authors.lastname: Hart
authors.forename: W S
authors.initials: WS
authors.lastname: Holbrook
authors.forename: K P
authors.initials: KP
authors.lastname: Furlong
authors.forename: T V
authors.initials: TV
authors.lastname: McEvilly
authors.forename: J A
authors.initials: JA
authors.lastname: Hole
authors.forename: S L
authors.initials: SL
authors.lastname: Klemperer