The plate-motion parameters of independently rotating Okhotsk and Amurian plates are consistent with the style of active deformation inferred from focal mechanism solutions. For example, our inversions predict right-lateral motion in northern Sakhalin, oblique contraction in southern Sakhalin, and little to no active deformation in the sub-marine crust north of Sakhalin. Predicted opening in the Baikal region is also consistent with historical seismicity and active structures.
Subtle changes in block and segment geometry (e.g. dip) within or near subduction zones can cause significant changes in the estimated pole of rotation of the Okhotsk plate. This is due, in large part, to the close proximity of most GPS stations in northeast Asia to these plate boundaries, such as the Kamchatka-Kurile subduction zone. GPS velocities on the Kamchatka peninsula and in Japan capture a complex pattern associated with the heterogeneously locked subduction zonethat may require more complex models. Additional blocks may also affect the determination of an independently rotating Okhotsk plate. Future work will examine the potential role of adjacent blocks such as the Philippine, Bering, northern Honshu, and Magadan blocks.
Berkeley Seismological Laboratory
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