A stochastic method for investigating site effects by means of a borehole array - SH and love waves

A stochastic method for investigating site effects by means of borehole arr ay observation is proposed. This method is based on a stochastic time-serie s model that is derived from Haskell's matrix procedure for a layered mediu m and is applicable to transverse-component recordings simultaneously obtai ned on the ground surface and at a depth. The time-series model not only ac counts for the amplitude but also for the phase characteristics of the reco rdings. By applying this method to actual downhole array recordings, the fo llowing aspects of site effects can be investigated: (1) An estimation of t he wave transfer function for SH waves, (2) the separation of upcoming and downgoing waves on a borehole seismogram at a depth, that is, an estimation of purely incident waves, and (3) the enhancement of fundamental mode Love waves on a surface seismogram are examined by applying this method to two borehole array recordings obtained at the Fuchu observatory in Japan. A not eworthy point is that these aspects of site effects are examined using this method without any knowledge of the velocity structure beneath the site.