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Rayleigh-wave amplitudes from earthquakes in the range 0–150° |
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| Authors: | J H Thomas PD Marshall A Douglas |
| Institution: | Department of Geological Sciences, University of Durham, Durham DHI 3LE;MOD (PE), Blacknest, Brimpton, Reading RG7 4RS |
| Abstract: | Summary . Vertical component Rayleigh-wave amplitudes from 1461 shallow earthquakes recorded in the distance range 0–150° are analysed to separate the effects of earthquake size, epicentral distance (Δ) and recording station. The estimated decay of amplitude with distance has the form of a theoretical curve for the decay of Rayleigh waves with distance if the assumption is made that the decay due to dispersion for the data analysed is that of an Airy phase. Writing the decay due to anelastic attenuation as exp (- k Δ), k is estimated to be 0.676/rad over the whole range of distance. If the distance effects are represented by a straight line of the form h log Δ+ constant, h is estimated to be 1.15. The calibration function for computing M Station effects on Rayleigh-wave amplitudes though statistically significant are small, and can probably be ignored in the computation of M Comparing the estimated surface-wave magnitudes (earthquake size) obtained in this study with the long and short period body-wave magnitudes ( m |
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