Seismic moments of major earthquakes and the rate of shortening across theTien Shan

Three Twentieth Century earthquakes that Richter assigned M greater than or equal to 8 and two of comparable magnitude in the Nineteenth Century imply rapid deformation within the Tien Shan. Seismic moment tensors of major ea rthquakes in this century suggest an average shortening rate of 7 (+/- 2) m m yr(-1) across the Tien Shan. In the western part, however, where three of the five largest earthquakes occurred, the calculated rate is consistent w ith the value of similar to 20 mm yr(-1) measured using GPS in that area by Abdrakhmatov et al. As Avouac et al. suggested, the high rate in the weste rn part apparently is a manifestation of counter-clockwise rotation of the Tarim Basin relative to Eurasia about an axis near the east end of the Tien Shan.