Abstract
This study deals with the identification of propagating direction of Rayleigh wave by spectral ratio between horizontal and vertical components of seismic ground motions at a site, which is called as H/V spectral ratio. The H/V spectral ratio of Rayleigh wave is well known to be imaginary, which means a phase difference of 90° between the horizontal and vertical components at the free surface. Using this fact, the index IQ (θ) is defined, which indicates the ratio of imaginary parts in the H/V spectral ratio of seismic ground motions. The propagating direction of Rayleigh wave is then estimated using the IQ (θ), in whose direction the IQ (θ) takes a maximum value. It has been shown from the numerical analysis that phase angles of H/V spectral ratio are concentrated on ±90° in the propagating direction of Rayleigh wave.
