Nonstationary ray decomposition in a homogeneous half space
© The Society of Geomagnetism and Earth, Planetary and Space Sciences (SGEPSS); The Seismological Society of Japan; The Volcanological Society of Japan; The Geodetic Society of Japan; The Japanese Society for Planetary Sciences; TERRAPUB. 2009
Received: 7 November 2008
Accepted: 26 August 2009
Published: 18 January 2010
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.