An intermediate depth earthquake beneath Tibet: source characteristics of the event of September 14, 1976.

Abstract

This paper presents the results of a detailed study of an intermediate depth earthquake beneath S Tibet (September 14, 1976; 0643:51.6 UT; 29.81oN, 89.57oE; focal depth 90 +- 10km; mb = 5.4). From the differences in arrival times of P, pP, and sP and from Rayleigh wave spectral densities the focus is estimated to be at depth of 90 +- 10km and therefore in the uppermost mantle. From the polarities of the first, motions of P waves, inversion of the relative amplitudes of P, pP, and sP, and synthesis of their waveforms, the source mechanism is constrained to be predominantly normal faulting with the T axis approximately horizontal and trending E-W. This mechanism is similar to those of shallow earthquakes in Tibet.-Authors