Estimation of Velocity Boundaries in a Sedimentary Layer-Basement System Using the Fuchu Array Recordings

A new method to estimate the velocity boundaries of real layered structure from only surface recordings was constructed by decomposing an SH-wave into instantaneous power of wave associated with rays in a homogeneous half space. The estimated results obtained by applying this method to seismograms were represented as a function of lapse-time (t) and depth-time (τ); i.e., travel time from surface toward depth-direction. We conducted the evaluation of the proposed method to the strong motion data recorded at the FCH array. The recordings were obtained using broadband velocity seismometers for the earthquakes that occurred in five source regions, the Eastern Yamanashi, East off Izu peninsula, in and around Tokyo, the Southwestern Ibaraki, and the Central Chiba regions. The estimated results of velocity boundaries obtained by this method were in good agreement with the velocity boundaries previously determined by means of down-hole method. The comparison study with seismic interferometry was also conducted, and yielded concordant results for the estimation of velocity boundaries.