Effect of continental and nearshore slopes on tsunami height

Abstract

In the present study, an attempt is made to understand the effect of continental and nearshore slopes on the transmission, propagation and run-up of tsunami. A numerical model study is carried out using shallow water equations that are solved using Crank-Nicolson finite difference approximation method on a staggered grid. A rectangular solitary wave is considered to propagate over typical continental slopes and nearshore profiles available along the Indian coast. The amplification or attenuation of tsunami characteristics over these cross-sections was studied. It was observed that the tsunami run-up is altered with varying continental slope, water depth on continental shelf and nearshore slope. The study suggests that tsunami height on the continental shelf increases for shallow continental shelf depths. The percentage increase in tsunami height with decrease in continental shelf depth from 200 m to 50 m is found to be 31%. Higher tsunami run-up was observed for deeper continental shelf and steeper continental slope, whereas lower tsunami run-up for deeper continental shelf and flatter continental slope. It was observed that for a steep continental slope (1:0.1), a reduction in nearshore slope (steep to flat) increases tsunami run-up up to a slope of 1:632 and then decreases.