THE CRUST VELOCITY STRUCTURE OF A PROFILE IN THE AREA OF EAST CHINA SEA AND ITS VICINITY
LUAN Xi wu 1) GAO Ge zhang 2) YU Pu zhi 1) ZHAO Jin hai 2) (1. Institute of Oceanology, Chinese Academy of Sciences, Qindao 266071 China; 2. Shanghai Programming and Design Institute of Marine Oil, Shanghai 200120 China)
Since 1982, the Institute of Oceanology, Chinese Academy of Sciences(IOCAS) has conducted more than 20 sonobuoy refraction measurement in the area of East China Sea. In 1991, the IOCAS also conducted OBS measurement in the same area. Both the our refraction data and other authors' refraction data measured in the area of East China Sea have been used to study the crustal velocity structure along a Profile which is across the East China Sea shelf basin, Okinawa Trough, Ryukyu Island, Ryukyu Trench and Philippine Sea in this paper. The ages of the velocity layer have also been determined in this paper. The crustal velocity structure is difference both along the chosen profile and from top to the depth. Along the profile there are three basins and three uplifts. From top to the depth there are 5 velocity layers, which are layers of 1.8～2.2 km/s, 2.4～2.8 km/s, 3.0～3.6 km/s, 4.5～5.1 km/s and 5.75～6.0 km/s. Based on the velocity structure we can know that the deposit environment was stable between Pliocene and Quaternary along the whole profile except the axis part of Okinawa Trough which had always been active and the deposit florescence was Eocene and the whole area was uplifting in the time of Oligocene and the sediments of that time upon the Diaoyudao uplift and Ryukyu island and also the area of East China Sea shelf basin and Okinawa Trough were denuded. The origination of the East China Sea shelf basin and the Okinawa Trough might be after the deposition of the velocity layer of 5.75～6.0 km/s.