Abstract
We conducted the MASW and Microtremor explorations at a Port and Airport Research Institute (PARI) site at Sendai, where borehole earthquake observation have been conducted and P-wave and S-wave (PS) logging in the boreholes had been released to the public. Under the PRENOLIN Project in France we got new boring data including PS logging and soil nonlinearity. Most of the MASW lines across the sites showed a homogeneous one-dimensional (1D) structure with a soft horizontal layer down to several (6∼7) meters. Also most of the microtremor data showed quite common horizontal-to-vertical (H/V) spectral ratios except for sites close to the office building, which also suggest the existence of a 1D structure at the site. Then we conducted 1D inversion analysis to obtain the best S-wave velocity structure that explains both observed H/V ratios and surface-to-borehole spectral ratios of weak earthquake ground motions. Although it is not the optimized structure, we obtained three quite similar structures based on three different initial models and searching ranges derived from previous PS logging, MASW, and new PS logging.
