Citation

Frankel A. Transp. Res. Rec. 1993; 1411: 1-8.

Copyright

(Copyright © 1993, Transportation Research Board, National Research Council, National Academy of Sciences USA, Publisher SAGE Publishing)

DOI

unavailable

PMID

unavailable

Abstract

Work being done at the U.S. Geological Survey on 3-D simulations of earthquake ground motions in sedimentary basins is described. The ultimate goal of this research is to predict strong ground motions in sedimentary basins for expected large earthquakes. Throughout this paper, the inadequacy of using flat-layered models for synthesizing ground motions in sedimentary basins is emphasized. It has been demonstrated with 2-D and 3-D simulations how the slope of the alluvium-bedrock interface can trap S-waves in the basins, producing prolonged trains of surface waves. These surface waves are not generated in flat-layered models, which underestimate the duration and peak amplitude of shaking. It is necessary to account for the increased duration and amplitude of surface waves in sedimentary basins when designing man-made structures with natural periods of 1 sec and greater.

RESULTS are presented for 3-D simulations of earthquakes on the San Andreas fault in the San Bernardino and Santa Clara valleys in California. These simulations show the importance of S-wave-to-surface-wave conversions at the edges of the valleys. A contour map of maximum ground velocity in the San Bernardino Valley is produced from the simulation of a magnitude 6.5 earthquake on the San Andreas fault. Areas of especially large ground motions occur where surface waves reflected from the edges of the basin constructively interfere with trapped waves behind the direct S-wave.

Record URL:
http://onlinepubs.trb.org/Onlinepubs/trr/1993/1411/1411-001.pdf

Language: en

Keywords

Mathematical models; Earthquake resistance; Finite difference method; Earthquake effects; Sedimentary rocks