Surface-Wave Amplitude-Versus-Distance Relation in the Western United States
Seismic data lab. rept.
TELEDYNE INDUSTRIES INC ALEXANDRIA VA EARTH SCIENCES DIV
Pagination or Media Count:
For epicentral distances less than 15 degrees in the Western United States, a new correction factor is proposed for use in the common Gutenberg formulation for surface-wave magnitude. The data on which this is based are 684 Rayleigh-wave amplitudes from Nevada Test Site explosions measured visually on the records of LRSM mobile stations and VELA observatories. The need for the variable T period in the magnitude calculation is discounted on empirical evidence. Magnitudes at distances less than 15 degrees when recomputed using the new correction factor are in excellent agreement with teleseismic magnitudes and show less scatter among themselves than previously. An estimate of the effective QR in the crust from the data is about 130. Amplitude losses should reflect other causes than anelasticity, and this value is undoubtedly much lower than the real QR.
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