HR: 0800h
AN: T31C-1318    [Abstracts]
TI: Crustal and Sub-Crustal Structure Beneath the Central Transverse Ranges of S. California
AU: * Yan, Z
EM: yanmei@gps.caltech.edu
AF: California Institute of Technology, MC252-21, CALTECH, Pasadena, CA 91125 United States
AU: Clayton, R W
EM: clay@gps.caltech.edu
AF: California Institute of Technology, MC252-21, CALTECH, Pasadena, CA 91125 United States
AB: We have constructed receiver functions for the SCSN stations in the Central Transverse Ranges of S. California. In addition to the Moho and some crustal interfaces, there is a prominent north-dipping interface at approximately 90 to 105 km in depth (Ps arrival time is 10-12 seconds relative to direct P). The reflector does not have the correct arrival time or ray parameter move-out to be a multiple of any crustal phase, and is a clear arrival on a number of stations. The structure could be part of the subducted Farallon Plate, but if so, it would contradict arguments that the slab has been stripped away in this area (Atwater and Stock, 1998). The depth of the interface also excludes the possibility of its being part of the captured Monterey plate by Pacific plate (Nicholson et al., 1994). The reflector also cross-cuts the drip structure reported by Humphreys and Clayton (1984). The reflector is only seen consistently for events from SW back-azimuth, for events from NW or SE, the interface is not clear. The reflector is also seen in several neighboring stations of LARSE II passive data, which complements the image from SCSN data. We have constructed three N-S profiles across the Central Transverse Ranges. The east one runs through the Precambrian basement rock of the east San Gabriel Mountains and only has a single mid-crustal interface. The central profile runs through the Mesozoic granite rock, and has two mid-crustal interfaces, which indicates significant lateral variations between the two profiles. On the west profile, the Moho depth has an abrupt change with the north end about 5-7 km deeper than the south end. These indicate that the crustal structure and Moho interface here are still closely related to the tectonic evolution history of this area, and that topography is not isostatically supported.
DE: 8120 Dynamics of lithosphere and mantle--general
DE: 7205 Continental crust (1242)
DE: 7218 Lithosphere and upper mantle
DE: 1208 Crustal movements--intraplate (8110)
SC: Tectonophysics [T]
MN: 2004 AGU Fall Meeting