Short-period S-wave attenuation under the United States

Abstract

A study of short-period S -wave spectra from deep events recorded at LRSM stations indicates severe attenuation of S waves under the Western United States. The average differential in ts * between the Eastern and Western United States was found to be ∼0.67 ± 0.19 sec (95 per cent confidence interval), which is several times greater than Δ tp * ∼ 0.2 - 0.25 for short-period P . This indicates that most, if not all, energy loss occurs in shear deformation. The numerical value of the ts * differential is also smaller than that derived from long-period spectra indicating a frequency dependence of Q .