Near-source observations and modeling of the Kuril Islands tsunamis of 15 November 2006 and 13 January 2007

摘要

Two major earthquakes near the Central Kuril Islands(M_w=8.3 on 15 November 2006 and M_w=8.1 on 13 January 2007)generated trans-oceanic tsunamis recorded over the entire Pacific Ocean. Thestrongest oscillations, exceeding several meters, occurred near the sourceregion of the Kuril Islands. Tide gauge records for both tsunamis have beenthoroughly examined and numerical models of the events have beenconstructed. The models of the 2006 and 2007 events include two importantadvancements in the simulation of seismically generated tsunamis: (a) theuse of the finite failure source models by Ji (2006, 2007) which providemore detailed information than conventional models on spatial displacementsin the source areas and which avoid uncertainties in source extent; and (b)the use of the three-dimensional Laplace equation to reconstruct the initialtsunami sea surface elevation (avoiding the usual shallow-waterapproximation). The close agreement of our simulated results with theobserved tsunami waveforms at the open-ocean DART stations support thevalidity of this approach. Observational and model findings reveal thatenergy fluxes of the tsunami waves from the source areas were mainlydirected southeastward toward the Hawaiian Islands, with relatively littleenergy propagation into the Sea of Okhotsk. A marked feature of bothtsunamis was their high-frequency content, with typical wave periods rangingfrom 2–3 to 15–20 min. Despite certain similarities, the two tsunamis wereessentially different and had opposite polarity: the leading wave of theNovember 2006 trans-oceanic tsunami was positive, while that for the January2007 trans-oceanic tsunami was negative. Numerical modeling of both tsunamisindicates that, due to differences in their seismic source properties, the2006 tsunami was more wide-spread but less focused than the 2007 tsunami.