HR: 0830h
AN: S51E-0105    [PDF]
TI: Azimuthal Dependence of Strong Ground Motions from Three California Earthquakes
AU: * Porter, L D
EM: ldporter@pacbell.net
AF: Geocarte International, PO Box 564, Alamo, CA 94507 United States
AU: Leeds, D J
EM: davidjleeds@aol.com
AF: David J. Leeds Associates, 11972 Chalon Road, Los Angeles, CA 90049 United States
AB: Strong ground motions from three major California earthquakes are studied for several station locations. Records from free field instruments for the 1971 San Fernando, 1989 Loma Prieta, and 1994 Northridge events are examined for epicentral distances up to 120 km. The radial and transverse components with respect to the station-epicenter directions are reviewed in terms of their time histories and spectra. In addition, the particle motions are evaluated for the three principal planes (horizontal, vertical-radial and vertical-transverse) associated with each station. The time histories and spectra for each of these components are computed. The objective of this study is to develop methods for estimating strong ground motions as functions of station azimuth with respect to source location and source mechanism orientation. Previous investigations have shown correlations between closely spaced stations which increase as the periods of the motions increase. Thus, displacements in station clusters generally show less variation than accelerations. The present analysis extends this approach by using spectra data and particle motions as additional tools to search for recognizable correlations between stations which are more widely spaced or symmetrically located (or nearly so) with respect to direction of the source mechanisms.
DE: 7200 SEISMOLOGY
DE: 7212 Earthquake ground motions and engineering
SC: Seismology [S]
MN: 2003 Fall Meeting