Seismicity of the Livermore Valley region, 1969-1981
In 1979 and 1980, LLNL installed a digitally recorded, event detected seismic network in the Livermore Valley region to augment the existing USGS Calnet stations. The data are routinely processed for P- and S-arrival times and epicenters are determined on a daily basis. The velocity model used was derived from P-wave travel times from 223 well-recorded earthquakes and five timed explosions which were inverted simultaneously for one- and three-dimensional velocity structure, station corrections, and hypocenters. Calculated station delays show a good correlation with geologic structure. The three-D inversions allow improved structural determination, but demonstrate little improvement in earthquake locations over the one-D inversion with station corrections. All recorded events from 1969 to 1981 were relocated using the 1-D model. Revised locations for earlier events in the Livermore Valley are closely correlated with seismicity recorded with the new, more dense network. Locations of events along the Hayward Fault are located slightly off of the fault trace, indicating that the model is less appropriate outside the confines of the valley. Seismicity patterns in the valley for the entire time-period show well-defined knots of activity along the Greenville, Marsh Creek, and Concord faults. A less well defined area of activity may be associated with either the Williams or Valle fault. In all cases first motion focal mechanisms are predominantly strike-slip, consistent with generally north-south compression.
- Research Organization:
- Lawrence Livermore National Lab., CA (USA)
- DOE Contract Number:
- W-7405-ENG-48
- OSTI ID:
- 5204076
- Report Number(s):
- UCRL-86969; CONF-820355-3; ON: DE82012700
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
580201* -- Geophysics-- Seismology & Tectonics-- (1980-1989)
CALIFORNIA
EARTHQUAKES
EPICENTERS
FEDERAL REGION IX
GEOLOGIC FAULTS
GEOLOGIC STRUCTURES
LAWRENCE LIVERMORE LABORATORY
NATIONAL ORGANIZATIONS
NORTH AMERICA
SEISMIC EVENTS
SEISMICITY
US AEC
US DOE
US ERDA
US ORGANIZATIONS
USA