THE NORTHWARD PROPAGATION OF THE ARC TECTONICS OF THE NORTHEAST PAMIR AND NORTHWEST TARIM BASIN

The geological, geographic and seismicity data indicate that three arc tectonic belt developed on the northeast Pamir, which was the south Pamir arc, the north Pamir arc and the external Pamir arc from south to north. In addition to these three belts, there are two nascent arc tectonic belts developed in its fore\|deep depression, the Kashi depression in the northwest Tarim basin, which is the northward propagation of the arc tectonics of northeast Pamir.The south Pamir is an ancient folded belt, composed of the Proterozoic metamorphic layers and igneous complex. It was pushed northward since the collision between the India and Asia, and uplifted since the end of the early Tertiary. The elevation of the Plateau is 4800～5300m, and several intermontane basins distributed in the plateau. At its northeast boundary is the Kalakorum right lateral strike slip fault. Strong strike slip earthquakes occurred along this fault. In the hinterland of the plateau, several normal faulting earthquakes occurred,which are consistent with the extensional dynamic environment of the south Pamir. Deep earthquakes occurred under the 70km depth crust of south Pamir. The N—S cross section of the focal depth show that the earthquake occurred within the south Pamir crust are lower than 70km, and the deep earthquakes with depth of 100～200km occurred in the crystal basement of Tarim basin which are under\|thrusting southward into the root of the south Pamir.