A Test of the Existence of the Eurasian - North American Plate Boundary on Sakhalin Island

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The configuration and motion of one of the largest lithospheric plates, North American, is very poorly understood in the large region of eastern Asia, where a wedge-like extremity of the North American plate is jammed between two larger plates, the Eurasian and Pacific plates. The main goal of this project is to determine if the North American and Eurasian plates converge on Sakhalin Island making 1000-km long plate boundary. The research relies on GPS surveys performed on Sakhalin between 1999 and 2006. Data from these surveys allow investigation of the strain accumulation on the island in terms of the viscoelastic crustal deformation at different stages of the earthquake cycle and, hence, to make a significant step forward in understanding the dynamics of the convergent plate boundary where subduction does not occur. The strain accumulation on Sakhalin Island is modeled at different stages of the earthquake cycle in order to determine if the velocity field is compatible with the Eurasia-North America relative motion or not. Discrepancies between GPS horizontal velocity vectors, earthquake slip vectors, and directions of relative plate motions in the southern Kuril Arc are being use in order to test whether the southern Kuril arc moves as predicted by the underthrusting of the Pacific plate beneath the North American plate or if there is a separate south Kuril sliver. The advantage of observations on Sakhalin is that the effect of the Pacific plate subduction on this island is small and can be reliably accounted for. Another advantage is that the system of faults on Sakhalin has been carefully mapped by geologic methods following the disastrous magnitude 7.0 (Mw) May 27, 1995 earthquake on northern Sakhalin.Unraveling and exploring the geometry, kinematics, and dynamics of interaction of such major plate as North America with adjacent plates in east Asia is an important problem in solid earth sciences. This problem has been debated for decades without much progress. This project is aimed at understanding the tectonics of the region neighboring one of the most densely populated countries, Japan. Sakhalin recently developed into the major supplier of oil and natural gas for eastern Asia. The oil and liquid natural gas pipelines run along the main Sakhalin fault, which is active seismically. Large disastrous earthquakes that killed thousands of people occurred on Sakhalin in the history and quite recently. This project will contribute to understanding the earthquake hazards in this part of the world.