Journal of Natural Disaster Science

RAPID ESTIMATION OF FAULT PARAMETERS FOR NEAR-FIELD TSUNAMI WARNING

Yasuo IZUTANI
Research Associate, Faculty of Engineering, Shinshu University
and
Tomowo HIRASAWA
Professor, Faculty of Science, Tohoku University

(Received 22 April, 1987 and in revised form 24 June, 1987)

Abstract

A simple method is presented for rapid determination of fault parameters which are necessary to evaluate sea-bottom deformation due to large shallow earthquakes. Making use of the directivity of strong motion duration derived from observed accelerograms, we can estimate the fault length and the direction of rupture propagation. The values of the fault width and the slip amount are estimated from empirical formulae with respect to the fault length. The dip angle and the slip angle are assumed to be those of the typical focal mechanism in the focal region of the earthquake concerned. Our method is applied to the 1968 Tokachi-Oki earthquake and the 1983 Japan Sea earthquake. The estimated values of the fault parameters are consistent with those obtained previously by other investigators through the analyses of far-field long-period seismic waves, aftershock distribution, and so on. It is concluded that the present method is applicable to near-field tsunami warning, provided that a sufficient number of digital accelerographs are installed with a good azimuthal coverage.

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