A systematic study of source time functions and moment tensors of intermediate and deep earthquakes

Abstract

We developed an inversion algorithm to determine the Source Time Function and Moment Tensor of intermediate and deep earthquakes from a set of teleseismic body wave records. The method proceeds in two stages. First, a nonlinear inversion by simulated annealing is performed to simultaneously (a) align the waveforms in time, (b) determine a common source time function, and (c) measure a collection of observed station amplitudes. The station amplitudes are then used, in a second stage, as secondary observables to invert for the moment tensors. We perform three different inversions to estimate the complete moment tensor solution, the pure deviatoric solution, and the double-couple solution. All the calculations are extremely simple and, in particular, it is mnot necessary to compute synthetic seismograms. The method requires well-isolated phases at different stations, which restricts its application to intermediate and deep events. The algorithm is applied to the FDSN broadband records corresponding to the period 1990-2005 of worldwide intermediate and deep seismicity (depth ≥ 100 km) of magnitude greater than 6.5. The source time functions are compared to those obtained from other studies of intermediate and deep events. The moment tensors are also systematically compared to the Harvard-CMT and USGS solutions. Both show a very good agreement with previous studies. Copyright 2007 by the American Geophysical Union.