Multiply-polarized shear-wave VSPs from the Cajon Pass Drillhole

Journal Article · Mon Aug 01 04:00:00 EDT 1988 · Geophys. Res. Lett.; (United States)

DOI:https://doi.org/10.1029/GL015i009p01001· OSTI ID:6773670

Daley, T M; McEvilly, T V; Majer, E L

A 3-component VSP data set was acquired in the Cajon Pass Drillhole, with multiply-polarized shear-wave source and a conventional P-wave source, producing a 9-component data set. The VSP data show effects on the full wavefield from the sediment-granite interface. Mode-converted waves are identified, with significant scattering of S-wave energy from the leading P-wavefront. Hodographs are used to display S-wave particle motions in two dimensions. Shear-wave splitting is observed in the hodographs. The shear-wave particle motion is used to infer anisotropy orientation with respect to the local strike of the San Andreas fault. Stress-induced fracturing is assumed to be a possible cause of the shear-wave splitting. A variation of particle motion orientation with depth is observed, implying a variation in anisotropy orientation as a function of depth.

• Research Organization: Center for Computational Seismology, Lawrence Berkeley Laboratory, University of California, Berkeley
• OSTI ID: 6773670
• Journal Information: Geophys. Res. Lett.; (United States), Journal Name: Geophys. Res. Lett.; (United States) Vol. 15:9; ISSN GPRLA
• Country of Publication: United States
• Language: English

Related Subjects

510100* -- Environment
Terrestrial-- Basic Studies-- (-1989)
54 ENVIRONMENTAL SCIENCES
BOREHOLES
CAVITIES
ELECTRIC LOGGING
GEOLOGIC FRACTURES
GEOLOGIC STRUCTURES
GEOLOGY
GRANITES
IGNEOUS ROCKS
PLUTONIC ROCKS
POLARIZATION
ROCKS
SEISMIC P WAVES
SEISMIC S WAVES
SEISMIC WAVES
SEISMICITY
SP LOGGING
STRATIGRAPHY
STRESSES
WELL LOGGING