SUMMARY

Moho structure of the East Sea based on 3D direct gravity inversion:
Implication for isostatic equilibrium state

Nguyễn Như Trung, Nguyễn Thị Thu Hương

In this paper, the satellite gravity and deep seismic data have been used to investigate the Moho depth of the East Sea based on the three calculated models: local isostatic compensation, correlation-regression and 3D direct gravity inversion. The comparison with deep seismic data (i.e. Sonobouy, OBS and ESP) reveals that the direct 3D gravity inversion solution gives the best result for estimating the Moho depth. 3D inversion has not only given the absolute depth of the Moho, but also provided the best correlation with the geological structures and tectonic factors in the region. The Moho undulations are related to the formation and evolution of the East Sea in Cenozoic. For example, strike-slip Red River and 110^o fault zone, in which the Moho undulations are NE-SW/E-W oriented; the Central Basin, Hoàng Sa and Trường Sa in which Moho undulations are NW-SE/N-S; the Manila subduction zone in which the Moho undulations are E-W oriented. Comparing the 3D Moho with Airy isostatic Moho and the gravity anomalies may divide the state of isostatic compensation of the region are in (1) nearly complete isostatic compensation in the northern, western and southwestern margin; (2) 80-90% isostatic compensation in the Central Basin and the southern margin; and (3) the Manila subduction zone could be an active zone, the state of isostatic compensation is not established.   

Ngày nhận bài: 30-7-2004

Người biên tập: Phạm Năng Vũ