Synthesis of Long-Period Surface Waves and Its Application to Earthquake Source Studies -- Kurile Islands Earthquake of October 13, 1963

Abstract

Normal mode solutions for a spherical earth model are superposed to obtain realistic synthetic surface waves for various force systems. The calculation of excitation functions is greatly facilitated by the variational technique. The effects of attenuation and instrument response are included in the synthesis. The synthesized seismograms are compared with the actual seismograms for wave form, amplitude, radiation pattern, and phase to obtain various source parameters such as force geometry, source-time function, seismic moment, source dimension, and rupture velocity. The application is made to the Kurile Island earthquake of October 13, 1963 (M = 8.3). The comparison is made for Love waves G_4 and Rayleigh waves R_4 for a period range 100 to 400 sec. It is found that a reverse dip-slip fault with a dip angle of 22° and a dip direction of N47°W can explain the observation reasonably well. Other parameters determined are as follows: seismic moment, 7.5×10^(28) dyne-cm; source-time function, step function; fault length, 200 to 300 km; rupture velocity, 2.7 to 4.5 km/sec in the direction N43°E.

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