Abstract
In recent earthquakes, a large number of houses on a filled valley ground were collapsed due to earthquakes vibration and landslides. In this study, ground motion characteristics of a filled valley were estimated by microtremor measurements and earthquake observations, at Oyumino in Chiba-city and Tama-Newtown in Hachioji-city. In these places, residential areas were developed on a large scale. The shear-wave velocity structure of the surface layers is modeled based on a large number of borehole logs in Oyumino. This model represents well the structure of the surface soil in Oyumino, and reproduces a suitable soil dynamics behavior, when compared to H/V ratios of microtremor. Based on the constructed soil model, vibration characteristics such as maximum amplification factors have been computed from the multiple reflection theory. In addition, we have evaluated peak ground acceleration (PGA) and peak ground velocity (PGV) by the equivalent linearizing analysis. By using these data, the ground motion characteristics of a filled valley ground were estimated.
