Seismic waves due to a shear fault in a semi-infinite medium. part II: Moving source

Abstract

Integrating a point source solution derived in the preceding paper by Kawasaki et al. (1973), theoretical surface displacements due to various types of propagating faults located in a semi-infinite medium are obtained and compared with those for an infinite medium. General features of wave forms are summarized as follows; (1) Except for SP wave and Rayleigh wave portions, horizontal components Ur and Uφ of free surface displacement are approximately given by doubling the corresponding displacements for an infinite medium. The vertical component Uz is much disturbed by the free surface. (2) The SP wave has an appreciable amplitude comparable to that of P wave as pointed out for a point source case by Kawasaki et al. (1973). Especially in such cases as shallow sources propagate upward, the SP wave becomes a remarkably marked phase. Hence, careful examinations for SP wave are required on analysing the near-field seismograms, especially for shallow focus earthquakes. © 1975, The Seismological Society of Japan, The Volcanological Society of Japan, The Geodetic Society of Japan. All rights reserved.