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The tsunami-zoning map (possible tsunami heights of a frequency of 1 event within 50 and 100 years) for the coast of the South Kuril Islands have been updated (former map have been developed in 2006). The update is based on the development of the tsunami-activity model, mainly due to the increase of the number of basic coastal locations (from 18 to 62) for which the parameters of the recurrence function were estimated, as well as on the modernization of the numerical model. Serious progress in simulations was achieved in setting the initial conditions, using the seismic tsunami source model. Field surveys on the coast to search for traces of historical and paleotsunami, as well as qualitative documentation of the Tohoku tsunami manifestations allowed to clarify the model of tsunami-activity in Southern Kuril Islands. The sufficiently large amount of data in this case (which is generally untypical for the tsunami) allowed authors, to apply the statistical approach for evaluation of the tsunami hazard distribution along the coast. Estimates of tsunami heights were spread from the basic coastal locations to adjacent parts of the coast using detailed simulation of all significant tsunamis and calculating wave heights at the shoreline. The detailed maps of tsunami-hazard at scale 1:100,000 have been made for the settlements of Yuzhno-Kurilsk, Kurilsk, Malokurilskoe, and Krabozavodskoe.

Storm surges (the significant sea level rises due to a drop in surface atmospheric pressure and an increase in wind velocity during the passage of deep cyclones over the coastal areas) pose a formidable threat to the coastal settlements of Sakhalin and the South Kuril Islands. As a result of flooding of coastal areas, the impact of storm waves on the shores and coastal facilities is sharply increased. The greatest damage caused by surges on 10.11.1990 and 9.11.1995 which affected the most populated southern part of Sakhalin Island. A long-term sea level series were analyzed, recorded at 9 coastal tide gauges located on the coast of Sakhalin Island and South Kuril Islands. Estimates for the maximum heights of the storm surges and tidal level were obtained separately, as well as for the rare recurrence of the total sea level height with the probability of these individual components superposition. The maximum total height of the sea level was obtained for the Kurilsk station, where the highest storm surge was recorded. The minimum values were obtained for southwestern coast of Sakhalin Island (Kholmsk and Nevelsk stations) were tides are small. Seasonal and inter-annual variations of strong waves were analysed from the data of visual observations.

The authors describe a two-dimensional (vector) regressional model for examining the anisotropic response of ice drift and ocean current velocity (“drift velocity”) to surface wind forcing. Illustration of the method is limited to sea ice response. The principal mathematical and physical properties of the model are outlined, together with estimates of the “response matrices” and the corresponding “response ellipses” (drift velocity response to a unity wind velocity forcing). For each direction, ϕ, of the wind vector the method describes a corresponding “wind factor” α(ϕ) (relative drift speed) and “turning angle” θ(ϕ) (the angle between the drift velocity and wind vector). The major ellipse axis corresponds to the direction of the “effective wind” (ϕ = ϕmax) and the minor axis to the direction of the “noneffective” wind. The eigenvectors of the response matrix define wind directions that are the same as the wind-induced drift velocity directions. Depending on the water depth and offshore distance, six analytical cases are possible, ranging from rectilinear response ellipses near the coast to purely circular response ellipses in the open ocean. The model is used to examine ice drift along the western shelf of Sakhalin Island (Sea of Okhotsk). Responses derived from the vector regression (four parameter) method are less constrained and therefore more representative of wind-induced surface motions than those derived using the traditional complex transfer function (two parameter) approach. [ABSTRACT FROM AUTHOR]

Ice-drift velocity records from coastal radar stations, combined with data from moored current meters and coastal wind stations, are used to examine sea-ice motion off the northeastern coast of Sakhalin Island in the Sea of Okhotsk. Ice motion is shown to be governed primarily by diurnal tidal currents and wind-induced drift, which explain 92%–95% of the total ice-drift variance. Diurnal tidal motions predominate off the northern Sakhalin coast, accounting for 65%–80% of the variance, while low-frequency wind-induced motions prevail off the south-central coast, accounting for over 91% of the ice-drift variance. Maximum diurnal tidal ice-drift velocities range from 90–110 cm s-1 on the north coast to 10–15 cm s-1 on the south coast, in good agreement with the barotropic model of Kowalik and Polyakov. The presence of diurnal shelf waves accounts for the strong diurnal currents on the steeply sloping northern Sakhalin shelf, while the absence of such waves explains the weak diurnal currents on the more gently sloping south-central shelf. Using a vector regression model, the authors show that wind-induced ice-drift “response ellipses” (the current velocity response to a unity wind-velocity forcing) are consistent with a predominantly alongshore response to the wind, with wind-induced currents most pronounced off the south-central coast where water depths are relatively shallow. Time–frequency analysis of wind and ice-drift series reveals that, in winter, when sea ice is most extensive and internally cohesive, the ice response is almost entirely aligned with the alongshore component of the wind; in spring, when sea ice is broken and patchy, the ice responds to both the cross- and alongshore components of the wind. [ABSTRACT FROM AUTHOR]