| Abstract: | A plausible seismo-tectonic boundary of the Sinkiang—Tibetan region is defined on the basis of the trend of higher magnitude earthquakes (M7.0) and energy released by them for the period 1905–1965. In order to study the nature of forces at the northwestern and eastern sides of the region focal mechanisms for eleven shocks have been determined using P-wave first-motion directions reported in the Bulletin of the International Seismological Centre (Edinburgh). Of these, seven mechanisms show thrust faulting, three strike-slip and one normal faulting. The sense of motions of underthrusting blocks in thrust-faulting mechanisms for the two sides are directed towards the Sinkiang—Tibetan region. The slip vectors of strike-slip faulting are also in agreement with the direction of movement of thrust faulting. Thus, the seismicity, energy released, slip vectors and the orientation of T-axes reflect that the northwestern and eastern sides of the Sinkiang—Tibetan region are the plausible seismo-tectonic boundary and the major earthquakes and higher crustal thickness are the results of the movements of surrounding plates towards the region. |
