Until recently, the Bering coast of Kamchatka was not considered as an area with a high level of tsunami risk despite the occurrence of 7.6 magnitude tsunamigenic earthquake near Ozernoy Cape in November of 1969. However, a series of 6.9-7.1 earthquakes occurred in 1989-1991 in the northern part of the Koryak autonomous region, have risen the public concern about the impeding large earthquake in this area. Since a large part of the potential seismic-prone area is located under the sea bottom, a future earthquake can generate a hazardous tsunami with the destructive effect for numerous fishing villages located on the sand spits, near the river estuaries and other low-lying areas. That is why the evaluation of tsunami risk for the Bering coast of Kamchatka was an essential part of the project on re-estimation of the seismic hazard for the Koryak autonomous region. Application of the conventional method of tsunamizoning, based on the straightforward stochastic evaluation of historical data, is not possible for this area due to nearly the absence of historical tsunami data. In this study we use the deterministic approach to this problem, based on delineation of potential tsunamigenic zones,assigning the source parameters for the so-called "design earthquake", application of numerical models of tsunami generation and propagation in order to obtain the computed mareograms at the important coastal points and their further analysis to estimate .the possible run-up heights along the coast.
Fig.1. Map of seismicity of north-western Kamchatka for the period from 1912 to 1992. The dotted lines show the position of potentially tsunami-prone zones.
Fig.2. Positions of model earthquake sources for tsunami computation.
Fig.3. Static bottom displacement for source N 1 (see Fig.2). Digits near isolines mean the vertical bottom displacement in cm. The solid dots indicate to the coastal points where computed mareograms were obtained. The inserted figure shows the position of these points on Ilpyrskaya Spit.
Fig.4. Perspective view (from the south-east) of the initial displacement of water surface for model source N1 (above) and the wave field at t=30 min after an earthquake (below).
Fig.5. Computed waveforms for model source N1 (position shown in Fig.2). The horizontal axis shows the time after an earthquake (in hours). The scale of the vertical axis (water level displacement) is shown on the left. Numbers near the computed waveforms correspond to the numbers of coastal points shown in Fig.3.
