Source parameters of moderate-sized earthquakes in the Tien Shan, central Asia from regional moment tensor inversion

We estimate faulting geometry, depth, and seismic moment of 32 moderate-sized earthquakes in the Tien Shan by matching observed and synthetic seismograms recorded at regional distances. The moment-tenser compression axes are oriented in the direction 170 degrees-350 degrees, consistent with the orientation of India-Eurasia convergence. This compression is manifested in reverse faulting on roughly east-west trending fault planes. Faults within the mountain system have moderate-to-steep dips, but range-bounding faults appear to dip more gently. Earthquake source depths are in the range 5-25 km, consistent with those determined from local earthquake studies. The distribution and mechanism of earthquakes in the Tien Shan suggests that a significant proportion of the active deformation in the Tien Shan is absorbed by shortening across intramontane basins. The absence of strike-slip earthquake mechanisms associated with the Talas-Ferghana Fault suggests that the fault is presently locked, with deformation accommodated on neighboring compressional structures.