Abstract
Records of strong motion are often used as the ground motion inputs in earthquake analysis and in the design of structures. The design of underground structures, however, requires more than just the time history at any particular point on the earth's surface. It also requires the space-time variation of the ground motion. We have therefore developed a method for generating a simulated space-time variation that includes strong ground motions recorded at observation points. This simulated variation is characterized by an apparent velocity and by a coherence function. Here we presented a case study using motion recorded during the 1940 Imperial Valley earthquake.
