Applicability and Bias of V-P/V-S Estimates by P and S Differential Arrival Times of Spatially Clustered Earthquakes

摘要

Estimating small-scale V-P/V-S variations at depth can be a powerful tool to infer lithology and hydration of a rock, with possible implications for frictional behavior. In principle, from the differential arrival times of P and S phases from a set of spatially clustered earthquakes, an estimate of the local V-P/V-S can be extracted, because the V-P/V-S is the scaling factor between the P and S differential times for each pair of earthquakes. We critically review the technique proposed by Lin and Shearer (2007), in which the mean value over all stations is subtracted from the differential arrival times of each pair of events in order to make the method independent of a priori information on origin times. The demeaned differential P and S arrival times are plotted on a plane, and the V-P/V-S ratio is estimated by fitting the points on this plane.