ABSTRACT
Data of nine deep seismic refraction lines located in South Sakhalin and near areas were reinterpreted on the base of 2-D inhomogeneous model in the Moscow State University. The seismic works were carried out by Institute of Earth Physics and Sakhalin Integrated Institute in 1963 – 1964 years. Computer technology of refraction traveltime inversion by homogeneous function method was worked out in Moscow State University. This technology is automatic simple 2-D inversion of system of refraction traveltime curves to velocity field. Using this technology it is possible to calculate seismic cross sections containing velocity values and values of velocity gradient for every point of it, boundaries, slope and steep faults, folding zones and other features. Length of the lines varies from 250 to 750 km. Detailed cross sections were obtained down to 30–60 km depth. The new seismic cross sections correspond to old ones in depth of major boundaries and velocity values in average only. These studies support, known tectonic model that active subduction zones “roll back” toward ocean. Remnants of oceanic plate and relic subduction zone are distinguished in the seismic cross sections and in the velocity maps of South Sakhalin. This relic subduction zone disposes in the rear of active Kuril arc. These cross sections were computed from observed seismic data without any preliminary proposals or initial models.
