Russian Journal of Earth Sciences
Vol. 6, No. 1, February 2004
The Sea of Okhotsk crust from deep seismic sounding data
V. B. Piip and A. G. Rodnikov
Abstract
The crustal structure of the Sea of Okhotsk was investigated by
way of reinterpreting the data obtained along 22 deep seismic
sounding (DSS) profiles. Eight profiles traversed the Sea of
Okhotsk. These seismic surveys were performed during the
International Geophysical Year in 1958-1959 by the researchers
from the Institute of the Physics of the Earth, USSR Academy of
Sciences. Seven profiles were surveyed in 1963-1964 near the
shores of Sakhalin Island by geophysicists from the Institute of
the Physics of the Earth (USSR Academy of Sciences) and from the
Sakhalin Multidisciplinary Research Institute. The new
interpretation of the seismic data confirmed the earlier ideas of
the reduced crustal thickness in the deep-sea basins of the Sea of
Okhotsk, such as, the Kuril Basin, the Deryugin and Tinro basins,
the sedimentary trough of the Tatar Strait, where the Moho surface
showed low boundary velocities of seismic waves, not higher than
7.6-7.8 km s-1. It appears that the sedimentary basins of the Sea
of Okhotsk reside above asthenospheric diapirs including magma
chambers. A system of rifts and spreading centers was mapped in
the northern and central parts of the Sea of Okhotsk, in the Tatar
Strait, and in the Kuril Basin. Paleosubduction zones that had
been active during the late Cretaceous and Early Paleogene time
and are marked by ophiolite belts at the present time have been
traced in the earth crust near the eastern shores of Sakhalin.
Remnants of paleosubduction zones were mapped using seismic data
in the Sea of Okhotsk along the Okhotsk-Chukotka volcanic belt,
which seem to be the fragments of a lithospheric plate that had
been going down under the active continental margin in Mesozoic
time.