Current deformation rates and extrusion of the northwestern Okhotsk plate, northeast Russia

Abstract

Northeast Asia is a region of broad deformation resulting from the convergence of the Eurasian (EU) and North American (NA) plates. Part of this convergence has been suggested to be relieved by the extrusion and deformation of the Okhotsk plate (OK). Three models for the deformation of the seismically active northwestern corner of the Okhotsk plate, based on different modes of deformation partitioning, are calculated and compared to observations from GPS, seismicity, and geology. The results suggest that this region is being extruded southeastward and deforming internally by a mixture of pure contraction, “smooth” extrusion, and “rigid” extrusion. Calculated extrusion rates are ∼3–5.5 mm/yr, comparable to estimates from geologic data, and internal deformation rates are ∼3.0 × 10 −9 yr −1 . Internal deformation may be only partially accommodated by seismicity, but the short time span of seismic data leaves this subject to large uncertainty.