Open Access

Nonstationary ray decomposition in a homogeneous half space

Earth, Planets and Space201061:BF03352983

https://doi.org/10.1186/BF03352983

Received: 7 November 2008

Accepted: 26 August 2009

Published: 18 January 2010

Abstract

Amethod for decomposing an SH-wave at the surface into the instantaneous power of shearing strain associated with rays in a homogeneous half space as a function of lapse time t and depth time τ, which is the travel time for the depth direction, is demonstrated. The instantaneous power in the (t, τ) space shows local maxima at the intersections of up-coming and down-going rays, which correspond to the velocity boundaries of the real layered structure beneath the site. Thus, the proposed method provides a tool for estimating the velocity boundaries of real layered structure from only surface recordings. The estimated results obtained by applying the proposed method to strong-motion data recorded at two Kanto sediment sites are in good agreement with the velocity boundaries previously determined by means of down-hole methods.

Key words

Ray decomposition Wigner-distribution instantaneous power velocity discontinuity