Collision and Extension at Continental Margins: Example of the Sea of Okhotsk

The crustal structure of the northern Sea of Okhotsk region was reworked after the relict Okhotsk Sea plate collided with Eurasia about 55 Ma. Post-collisional extension and magmatic processes were likely initiated within the Okhotsk Sea plate and Asian margin along the remnant convergent plate boundary. The crustal structural pattern differs from the north and from the south by the remnant plate boundary. To the north, a series of northeast trending normal faults started to form during the Eocene extension within the Asian margin after collision with the Okhotsk Sea plate. To the south, a series of southeast trending normal faults was initiated due to extension within the Okhotsk Sea plate during the latest Oligocene through Early Miocene. Formation of Eocene volcanic rocks likely marks the magmatic processes which occurred at the beginning of Tertiary extension in the Sea of Okhotsk. Further studies are relevant to evaluate of earthquake potential and crustal movement along the remnant plate boundary and to correlate the deformation events within the Okhotsk Sea plate with the arc-continent collision event occurred at Kamchatka about 55 Ma. This work is funded by Russian Science Support Foundation.