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  • Article
  • Open Access

Nonstationary ray decomposition in a homogeneous half space

Earth, Planets and Space201061:BF03352983

  • Received: 7 November 2008
  • Accepted: 26 August 2009
  • Published:


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