Preliminary study on isostatic anomaly and recent tectonic stress field

Abstract

On the basis of the reality of recent tectonic movement and discarding such a viewpoint that the isostatic adjustment only results from excessive or insufficient compensation, we have discussed the tectonic stress causing inequality and regarded the isostatic anomaly as a load on the earth’s interior, thus the earth’s inner stress can be calculated. The research results show that in the East China Sea and its eastern marginal seas the change of the vertical stress derived from the isostatic gravity anomaly is more marked than that of the horizontal stress. Along the Ryukyu trench there is an enhancement of vertical stress by 5 MPa, which evidently reflects the effect of plate subduction. On contrary, along the island arc to the northwest of the trench the vertical stress weakens by about 5 MPa. The horizontal stresses in eastern and western parts are obviously different, the east westward stress on the oceanic crust σxis negative (while the pressure is positive) but on the continental crust is positive. These facts indicate the effect of compression between plates.