MOMENT TENSOR ESTIMATION USING REGIONAL SEISMOGRAMS FROM A TIBETAN PLATEAU PORTABLE NETWORK DEPLOYMENT

We present the results of moment tenser inversions using regional seis mograms recorded during the 1991-1992 PASSCAL passive seismic experime nt on the Tibetan Plateau. Using data recorded over a one-year period, we estimate the source mechanisms for 38 earthquakes within and near the Tibetan Plateau with moment-magnitudes (M(w)) ranging from 3.8 to 5.0. With only one exception, all the events within the Plateau, but a way from the Plateau boundary, indicate either strike-slip or extensio nal faulting, a result consistent with previous studies. Three-fourths of all the events occurred at depths less than 10 km, and all but two depths less than 15 km. Several events, located near the southeastern section of the Plateau, exhibit an unusual m(b)-M(w) difference of ap proximately one magnitude unit.