2004 Giant Earthquake at the Indian Ocean has had the possibility of slow slip on the fault around Andaman Islands. When sea bottom motion is slow, we cannot predict accurately tsunami by using the initial tsunami profile applied sea bottom deformation. Then, the authors showed effects of sea bottom motion on tsunami by using the free sea surface applied gradually sea bottom deformation in consideration of rise time and rupture velocity. This study has two stages: tsunami in the constant depth and tsunami in the actual bathymetric feature. Here we carried out the case study of 2004 Indian Ocean Tsunami.

INTRODUCTION

Initial tsunami profile is generally given by applying sea bottom deformation to the free sea surface, assuming that sea bottom motion is instantaneous. Therefore, we cannot predict accurately initial tsunami profile with the above method in the situations when the sea bottom motion is slow, such as Giant Earthquake and Tsunami at the Indian Ocean in 2004 that showed the possibility of slow slip on the fault around Andaman Islands (Lay et al., 2005). There are some phenomena which could have the conditions when we can't assume that sea bottom motion is instantaneous, such as volcanic sea bottom motion, submarine landslide, slow slip on the rupture surface and so on. In this study, we consider various sea bottom motions by temporal characteristics of source rupture process, such as rise time, rupture velocity and rupture propagation direction. Rupture velocity is defined as velocity to which rupture front spreads. Rise time is defined as rupture duration at local area on the rupture surface, i.e., time from arrival time of rupture front to finish time of rupture. If period of a tsunami is related closely to natural period of a harbor, the tsunami in the harbor is amplified by the succeeded wave.

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