Sedimentary P- and S-Wave Velocity Structures in Shimousa Region of Kanto Basin Determined from Joint Autocorrelation and Receiver Function Analysis

To determine the P- and S-wave velocities (VP and VS, respectively) of the sedimentary layers in the Shimousa region of the Kanto basin, Japan, the autocorrelations of P and S waves and the receiver function (RF) for the local earthquakes at the strong-motion stations in the region were jointly analyzed. Because the autocorrelations and RF were insensitive to the event location, the stacked functions for various events captured clear P and S reflections and the Ps phase at the bedrock of the basin. The PpPs phase was also clearly observed at some stations in the region. The arrival times of the P and S reflections and the Ps phase depended on the station. These phases arrived earlier at the northern and eastern parts of the region, and later at the southern and western parts. This trend shows good agreement with that expected from the 3D velocity structure model developed by the Japan Seismic Hazard Information Station. The VP, VS, and thickness (H) values were then estimated from the histogram of the H-V stack for the P and S autocorrelations and the Ps and PpPs phases in the RF. VP, which is less sensitive than VS and H, was not always well determined at some stations, whereas VS and H were well estimated with high resolution. It was found that the resolution depends on the station location in the region. This dependence could be caused by the appearance of clear phases in the functions.