TSUNAMIS GENERATED BY SUBAQUATIC VOLCANIC EXPLOSIONS: UNIQUE DATA FROM 1996 ERUPTION IN KARYMSKOYE LAKE, KAMCHATKA, RUSSIA

Abstract

The 1996 subaquatic explosive eruption near the northern shore of Karymskoye Lake in Kamchatka, Russia, generated multiple tsunamis. We document the explosive process that produced the tsunamis, and describe the tsunami effects and runup around the 4-km diameter lake. These data enable the determination of an attenuation relation of runup (wave) height for these ‘‘explosive’’ tsunamis, which is compared with theoretical models of wave height distributions. For the proximal zone, involving radial distances (r) up to 1.3 km from the source, the runup height (R) shows rapid attenuation (from \30 m to 8 m) with distance as log R= −1.98 log[r]+2.6. For the distal zone, r\1.3 km, involving mainly wave travel southeastwards along the body of the lake away from the explosion source, R decays more slowly (from 8 m to 3 m) as log R= −0.56 log[r]+1.9. Rapid decay in the proximal zone suggests that near the source of the explosion, the tsunami propagated radially as a collapsing wave (bore) with discontinuous change in height. The break-in-slope of the runup plot at 1.3 km suggests that beyond this distance the tsunami propagated approximately as a decaying one-dimensional wave in a channel of approximately constant width.