P-velocity models and earthquake locations in Livermore Valley region, California

Journal Article · Sun Aug 01 04:00:00 EDT 1982 · Bull. Seismol. Soc. Am.; (United States)

OSTI ID:6219109

Taylor, S R; Scheimer, J F

P-wave travel times from 223 well-recorded earthquakes and five timed explosions recorded by the US Geological Survey-Lawrence Livermore National Laboratory seismic network are inverted simultaneously for one- and three-dimensional velocity structures and hypocenter locations. The stability of earthquake locations between the one- and three-dimensional inversions demonstrates the adequacy of a layered earth model combined with station corrections for routine hypocenter locations in the Livermore Valley. Initial one-dimensional velocity inversions indicate a fairly strong positive velocity gradient in the upper crust of about 6 km. Three-dimensional models show that the strongest velocity contrasts occur along the eastern and southern edges of the valley where lower velocity down-dropped Tertiary sediments and basin-full alluvium are found in structural contact with higher velocity Late Mesozoic and Tertiary sediments of the Altamont anticline and the Diablo Range. The low-velocity basin structure is truncated along the western margin of the Livermore Valley by the Calaveras fault across which higher velocity aftershocks from the Livermore are exposed. Some of the relocated Cretaceous and Tertiary formations earthquake sequence show a good correlation with surface trace of the northwest-trending Greenville fault. In the southeast corner of the Livermore Valley, a number of short (5 km or less), linear, and discontinuous epicentral zones are observed. These seismic lineations appear to define a conjugate set of right-stepping faults in a right-lateral shear zone. Focal mechanisms for these aftershocks show many complexities, but are generally consistent with this interpretation.

• Research Organization: Lawrence Livermore National Lab., CA
• DOE Contract Number: W-7405-ENG-48
• OSTI ID: 6219109
• Journal Information: Bull. Seismol. Soc. Am.; (United States), Journal Name: Bull. Seismol. Soc. Am.; (United States) Vol. 72:4; ISSN BSSAA
• Country of Publication: United States
• Language: English

Related Subjects

58 GEOSCIENCES
580201* -- Geophysics-- Seismology & Tectonics-- (1980-1989)
CALIFORNIA
EARTHQUAKES
ERRORS
FEDERAL REGION IX
GEOLOGY
LAWRENCE LIVERMORE LABORATORY
MEASURING INSTRUMENTS
NATIONAL ORGANIZATIONS
NORTH AMERICA
RISK ASSESSMENT
SEISMIC ARRAYS
SEISMIC DETECTORS
SEISMIC EVENTS
SEISMIC P WAVES
SEISMIC WAVES
US AEC
US DOE
US ERDA
US ORGANIZATIONS
USA
WAVE PROPAGATION