Source effects on strong-motion records and resolving power of strong-motion arrays for source inversion

Abstract

Source effects are dominant in near-source strong-motion seismograms, even in the high-frequency range, and source inversion is the most powerful tool for investigating source effects. First, source effects that are closely related to damage and intensity patterns are briefly shown. Large inconsistencies have been seen among source inversion results. The cause seems to come mainly from insufficient station distribution for earthquake source studies. However, the deployment strategy of strong-motion seismographs has been only poorly explored. Secondly, three kinds of simulations conducted for the last several years are shown, in order to indicate the vulnerability of the resolving power of strong-motion arrays to a source inversion. The simulations are: 1. (1) to obtain a relationship between the accuracy of the source inversion and fault-array parameters; 2. (2) to present the optimum array geometry for the source inversion; and 3. (3) to describe the relative significance of various seismic waves in the source inversion. Thirdly, basic guidelines on strong-motion array layout for source inversion are provided and general comments are given on actual source inversion methods. We find that the physical wave is a key concept for understanding the optimum array configuration and for choosing the most pertinent inversion method. Frequency consideration, which is a remaining problem, is required to decide the best inversion method and the best array layout. We can design strong-motion array for source inversion on the condition that frequency contents, fault mechanism, the spatial resolution and the inversion accuracy are prescribed.