EARTHQUAKE SLIP DISTRIBUTION FROM TSUNAMI DEPOSITS AND TSUNAMI SIMULATIONS: THE 1952 KAMCHATKA EVENT

We use the 1952 Kamchatka earthquake (Mw 8.8-9.0) and tsunami to explore the effect of earthquake slip distribution on tsunami amplitude in the nearfield— we ask the question “can tsunami deposits be used for determining source characteristics of a tsunami-generating earthquake?” Because earthquake histories for regions susceptible to tsunamis are important for vulnerable communities, this question is inevitable. Direct measurements such as tsunami runup and inundation for paleo-events or events occurring in remote localities can be scarce; sediment deposited by a tsunami is often the only trace remaining of the event. To connect tsunami sediment with earthquake-source characteristics, we compare 1952 Kamchatka tsunami deposits with simulated tsunami runup in the nearfield. Variation in deposit distribution indicates variation in runup, which helps us identify regions where large deflections of the water surface within the earthquake rupture area, interpreted as high slip on the subduction zone, are required to produce the deposits. Deposits from the 1952 Kamchatka tsunami indicate runup was at least ~ 20 m in southern Kamchatka and the northern Kuril Islands, as opposed to ~5-10 m in other nearfield coastal areas. Simulated propagation and inundation from tsunamis with different slip distributions indicate that in order to create observed tsunami deposits, there were regions of high slip off southern Kamchatka during the 1952 earthquake. Modeling also confirms that peaks in nearfield tsunami amplitude generally occur adjacent to regions of high slip. Changes by at least a factor of two in the amount or location of slip have noticeable effects on runup of simulated tsunamis, while smaller-scale changes do not significantly alter the variation in near-field tsunami amplitude.