Tsunamigenic predecessors to the 2009 Samoa Earthquake.

Abstract

We analyze historical earthquakes of the past century having generated regional tsunamis in Samoa, by means of epicentral relocation and quantification of spectral amplitudes of waveforms from historical seismograms. The only tsunami with a level of destruction comparable to the 2009 event was generated by the earthquake of 26 June 1917 in the Samoa corner. Yet, a memory of this event is largely absent from the ancestral heritage of the present population of Samoa, which we tentatively attribute to the nearly simultaneous occurrence of the influenza epidemic in 1918. While not able to fully resolve focal geometries, we document a diversity of mechanisms, which add an element of unpredictability to the forecast of any future tsunami in the region. (C) 2011 Published by Elsevier B.V