A STUDY OF STRONG EARTHQUAKES AND THE TECTONIC STRESS FIELD OF SOUTHWESTERN CHINA AND ITS ADJACENT AREAS

The present paper has employed the finite-elements method in association with planes to study the relationships between the tectonic stress field and the earthquake occurrences in Yunnan province. Computations are divided into two steps: first for the stress field of a broad region, then for a smaller one. The relationships between the activities of strong earthquakes in Southwest China and its adjacent areas and the tectonic stress field are dealt with in detail.The results of the computation indicate: 1) The uneven pushing from the south due to the Indian Plate is the principal cause of the very eomplicated nature of the tectonic stress field of Southwest China under specific boundary conditions; 2) Under the action of the Indian Plate, relative movements between individual tectonic - blocks and large-scale stress field readjustments within the plate are the principal cause of the activities of strong earthquakes in Southwest China; 3) In the light of the study of the readjustment of the stress field during the 4 earthquakes greater than magnitude 8 (the Haiyuan, Gulang, India-Nepal and Chayu earthquakes), the author has got the impression that future earthquakes greater than magnitude 8 are likely to hit the Shichuan-Yunnan-Tibet or the Burma regions.