Abstract:
Seismic activity in southern Sakhalin is related to zones of submeridionally striking faults (upthrow and normal faults) separating ridges and intermountain depressions, and transorogenic faults of the NW (sinistral strike-slip faults) and NE (dextral strike-slip faults) strike. The observed system of active faults corresponds to a stereotype of fractures resulting from sublatitudinal and diagonal (azimuth 305°) horizontal compression. The seismic activity along the western side of the Susuya intermountain depression in the mid-Quaternary shifted from the Tym-Poronai fault, crosscutting the Pliocene-Early Quaternary and mid-Quaternary leveling planes, to the Aprelovka fault, displacing the Late Pleistocene and Holocene assemblages. The Lower Pleistocene deposits of the Susuya depression occur conformably together with Pliocene assemblages of a molasse formation (Maruyam suite). Since paleoseismodeformations indicating catastrophic Holocene earthquakes are known over the entire territory of the island, including regions currently aseismic, it is demanded that a study of active faults be performed in the whole territory of Sakhalin and adjoining water areas aimed at diagnosing earthquake frequency and a long-term prediction of seismic hazards.