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Source Parameters of Earthquakes from Spectra of Rayleigh Waves

1971; Oxford University Press; Volume: 22; Issue: 4 Linguagem: Inglês

10.1111/j.1365-246x.1971.tb03606.x

1365-246X

Agustín Udías,

Seismic Waves and Analysis

A generalized form of the directivity function has been used to determine the length and the rupture velocity of four earthquakes with known vertical strike slip faulting. For body wave magnitudes between 5.7 and 7.0, the lengths vary from 18 to 35 km with a rupture velocity of 1.5 kms−1. Seismic moments have been determined from the spectral amplitude densities and the theoretical response to a point source model. From these values, stress drops of 2 to 30 bars and average dislocations of 4 to 160cm have been derived. The products of the average stresses acting at the fault by the seismic efficiency factor are of the order of 107 dyne cm−2 for all four earthquakes; this seems to indicate a minimum strength of the crust under horizontal shear stress of the same order.