Generation of tsunami by a fault model.

Abstract

Characteristics of tsunami waves caused by a fault model are investigated theoretically in detail. Effect of focal parameters on tsunami amplitudes, relation with the static deformation at the source area, sense of initial motion and directivity are discussed.Main results are summarized as follows: The dip-angle, fault length and focal depth play important roles in the generation of tsunami. As an estimate of the directivity, we define an index α, which is the ratio of the maximum amplitude in the wave train at φ=90°, where φ is measured from a direction along the strike of the fault plane, to that at φ=0°. The index α is strongly affected by the change of the dip-angle and the ratio (fault width)/(fault length). The moving directions of initial motions of tsunami waves at φ=90° and 270° reflect the sense (upheaval or subsidence) of the static deformation but not at φ=0°.