Near-field propagation of tsunamis from megathrust earthquakes.

Abstract

We investigate controls on tsunami generation and

propagation in the near-field of great megathrust earthquakes

using a series of numerical simulations of subduction and

tsunamigenesis on the Sumatran forearc. The Sunda

megathrust here is advanced in its seismic cycle and may be

ready for another great earthquake. We calculate the seafloor

displacements and tsunami wave heights for about 100

complex earthquake ruptures whose synthesis was informed

by reference to geodetic and stress accumulation studies.

Remarkably, results show that, for any near-field location:

(1) the timing of tsunami inundation is independent of slipdistribution

on the earthquake or even of its magnitude, and

(2) the maximum wave height is directly proportional to the

vertical coseismic displacement experienced at that location.

Both observations are explained by the dominance of long

wavelength crustal flexure in near-field tsunamigenesis. The

results show, for the first time, that a single estimate of vertical

coseismic displacement might provide a reliable short-term

forecast of the maximum height of tsunami waves.