TSUNAMI AMPLIFICATION ALONG THE EASTERN COAST OF INDIA AND SRI LANKA DUE TO EARTHQUAKE RUPTURE PROPAGATION IN THE SUMATRA-NICOBAR-ANDAMAN TRENCHES

摘要

We investigated an effect of earthquake rupture propagation, or tsunami source propagation, on offshore tsunami amplitude through numerical simulations. In the numerical simulations, we used satellite-based real bathymetry and a realistic fault configuration for M9 class great earthquakes, and we allowed an earthquake rupture to propagate one-dimensionally in the long-axis direction of the fault. Various earthquake rupture velocities as well as various fault lengths were tested. A general feature is that the slower the earthquake rupture velocity, the larger the tsunami amplitude. This suggests that the effect of earthquake rupture propagation cannot be neglected for most of tsunamis generated by slow earthquakes. Along the eastern coast of India and Sri Lanka, however, earthquake rupture propagation makes tsunami amplification behaviors complicated and varied from station to station. This is because amplification of offshore tsunami is controlled by source configuration and bathymetry as well as rupture velocity.