On shear-wave splitting in the Los Angeles basin

摘要: Three-component seismograms at the three USC stations, PVP, GFP and DHB, have been examined. Most earthquakes, with magnitudes ranging from 1.4 to 5.0, within a period 1985 1988, show evidence of shear-wave splitting. The preferred polarization first split-shear wave arrivals PVP is nearly in N-S which consistent both regional maximum horizontal compressive stress direction local subsurface fault strike, showing that splitting caused by liquid-filled cracks or fractures associated faulting. polarizations shear are roughly divided into two almost perpendicular directions, ENE-WSW NNW-SSE, parallel strike geology topography near station. Because foothills Santa Monica Mountains, may be disturbed topographic irregularities dipping interfaces. Two examples DHB clearly display Their N-S, agree fragmentary surface fracturing there. From some relatively reliable delay times, crack densities stations given, is, 0.025 0.020 0.045 DGB. No systematic change discovered this study.