Tsunamis generated by subaquatic volcanic explosions: Unique data from 1996 eruption in Karymskoye Lake, Kamchatka, Russia

The 1996 subaquatic explosive eruption near the northern shore of Karymskoy e Lake in Kamchatka, Russia, generated multiple tsunamis. We document the e xplosive process that produced the tsunamis, and describe the tsunami effec ts and runup around the 4-km diameter lake. These data enable the determina tion of an attenuation relation of runup (wave) height for these "explosive " tsunamis, which is compared with theoretical models of wave height distri butions. 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 sugge sts 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 c hannel of approximately constant width.