渤海陆缘地震的力学特征和成因

渤海陆缘是华北强震活动区,如1966年的邢台震群,1967年的河间地震,1969年的渤海地震,1975年的海城地震,1976年的唐山震群和1983年的菏泽地震,都是在该区发生的。显然,深入研究该地区的构造运动和地震成因是有重要科学意义的。本文拟从应力场角度进行研究。

MECHANICAL FEATURES AND SEISMOGENIC PROCESSES OF CONTINENT-MARGINAL EARTHQUAKES AROUND BOHAI BAY

Around the continental margin of Bohai Bay, many strong earthquakes occurred recent years. They are similar to each other as regards the mechanical features of seismic sources and their relation of seismogenic processes. After analyzing synthetically the data of earthquakes, geology, geophysical exploration and geotherm, we consider that there exist two tectonophysi-cal processes at work in the area of continental margin of Bohai Bay. One is due to the interaction between the fracture belts oriented in NNE under the maximum principal compression stress oriented in NEE, the valley system of North China Plain was formed. Another is due to the inhomogeneous geothermal activity from the earth's interior, the upper mantle of this area was locally uplifted and the value of heat flow was increased. For them, the corresponding mechanical models are presented and the stress field of them are calculated in this paper. It is found that the areas of strong earthquakes always agree with the high value area of the combined stress field.