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A method is described which uses the relative amplitudes of related seismic phases to impose constraints on the form of the P and S wave radiation patterns, from which a moment tensor determination is obtained complete with a well‐founded measure of its precision. Two types of teleseismic relative amplitude measurements may be employed: those relating P , pP , and sP and those relating the three components of the direct S wave. Examples are given which apply the method to (1) smaller shallow earthquakes ( m b ≲ 5.5) recorded at short period, (2) larger intermediate‐depth and deep earthquakes ( m b ≳ 5.8) using long‐period seismograms, and (3) large m b shallow earthquakes, which require both P and S wave data at long period. The relative amplitude moment tensor program (RAMP) is an advance on the relative amplitude method of Pearce 1977, 1980 in that the a priori double couple assumption is now relaxed. Results are compared with those of other moment tensor methods where available. RAMP is found to be a sensitive indicator of volumetric source component even for small data sets, for which it is less good at discriminating between different constant‐volume source types, notably the double couple and the compensated linear vector dipole. Since current inverse methods presume a constant‐volume source, our method alone is a reliable indicator of volumetric component, which is important for the analysis of source processes and in earthquake‐explosion discrimination.
Pearce et al. (Tue,) studied this question.