HR: 0830h
AN: S21F-0386    [PDF]
TI: Seismicity and Lithospheric Structure in Southern California
AU: * Christina, W
EM: cw26@st-andrews.ac.uk
AF: US Geological Survey, 345 Middlefield Rd., Menlo Park, CA 94025 United States
AU: * Christina, W
EM: cw26@st-andrews.ac.uk
AF: University of Durham, University Office, Durham, DH1 3HP United Kingdom
AU: Mooney, W D
EM: mooney@usgs.gov
AF: US Geological Survey, 345 Middlefield Rd., Menlo Park, CA 94025 United States
AU: Detweiler, S
EM: shane@usgs.gov
AF: US Geological Survey, 345 Middlefield Rd., Menlo Park, CA 94025 United States
AB: Southern California is a region undergoing continued deformation. Movement between the North American and Pacific plates manifests itself in high levels of seismicity. In this study we investigate the relationship between deeper structure and the seismicity of southern California. Our investigation is made possible by the release of the SCEC 3.0 Velocity Model, which incorporates the upper mantle. Primary consideration is given to the mantle downwelling centred below the Transverse Ranges. Relationships are sought with the depth, distribution and frequency of earthquakes. A wide variety of data sources are utilized and both existing and specially designed programs are used to manipulate the data, resulting in a synthesis of the regional seismicity and tectonics. Deep seismicity is found to preferentially occur in regions overlying the high-velocity upper mantle "drip". This observation is consistent with depressed isotherms. Large events appear to cluster in crust overlying high-velocity regions, however small events are almost uniformly distributed between the fast and slow regimes. This suggests no measurable variation in crustal strength, however this might be clarified with the removal of aftershock events. There is no evidence for subduction beneath the Transverse Ranges.
DE: 7205 Continental crust (1242)
DE: 7218 Lithosphere and upper mantle
DE: 7230 Seismicity and seismotectonics
DE: 8110 Continental tectonics--general (0905)
DE: 8124 Earth's interior--composition and state (old 8105)
SC: Seismology [S]
MN: 2003 Fall Meeting