INVESTIGATING EARTHQUAKE HAZARDS IN THE SALTON TROUGH, SOUTHERN CALIFORNIA--THE SALTON SEISMIC IMAGING PROJECT (SSIP)
FUIS, Gary S.1, SICKLER, Robert R.1, GOLDMAN, Mark R.1, ROSE, Elizabeth J.1, MURPHY, Janice M.1, FERGUSON, Alex J.1, HOLE, John A.2 and STOCK, Joann M.3, (1)Earthquake Hazards Team, U.S. Geological Survey, 345 Middlefield Rd, Menlo Park, CA 94025, (2)Geosciences, Virginia Tech, Blacksburg, VA 24061, (3)Seismological Laboratory, California Institute of Technology, 1200 E California Blvd, MC 252-21, Pasadena, CA 91125, fuis@usgs.gov
The Salton Seismic Imaging Project (SSIP) is a collaborative effort between academia and the U.S. Geological Survey to provide detailed, subsurface 3-D images of the Salton Trough of southern California and northern Mexico. From both active- and passive-source seismic data that were acquired both onshore and offshore (Salton Sea), the resulting images will provide insights into earthquake hazards, rift processes, and rift-transform interaction at the southern end of the San Andreas Fault system. The southernmost San Andreas Fault (SAF) is considered to be at high-risk of producing a large damaging earthquake, yet the structure of this and other regional faults and that of adjacent sedimentary basins is not currently well understood.
Seismic data were acquired from 2 to 18 March 2011. One hundred and twenty-six borehole explosions (10-1400 kg yield) were detonated along seven profiles in the Salton Trough region, extending from area of Palm Springs, California, to the southwestern tip of Arizona. Airguns (1500 and 3500 cc) were fired along two profiles in the Salton Sea and at points in a 2-D array in the southern Salton Sea. Approximately 2800 seismometers were deployed at over 4200 locations throughout the Salton Trough region, and 48 ocean-bottom seismometers were deployed at 78 locations beneath the Salton Sea. Many of the onshore explosions were energetic enough to be recorded and located by the Southern California Seismograph Network.
The geometry of the SAF has important implications for energy radiation in the next major rupture. Prior potential field, seismicity, and InSAR data indicate that the SAF may dip moderately to the northeast from the Salton Sea to Cajon Pass in the Transverse Ranges. Much of SSIP was designed to test models of this geometry.
