High-Resolution Seismic Reflection Survey Using Land Streamer In A Large Urban Area

High-resolution shallow seismic reflection surveying using SH-wave type Land Streamer was<br>conducted in the Tokyo Metropolitan area, where more than 25 million inhabitants concentrate in small<br>but highly developed region of 3,500 square km. While seismic reflection surveys have been frequently<br>conducted in the area to delineate relatively deep geologic structure, shallow reflection surveys have<br>been exceptional due to the difficulty in surveying at such a high land-use area as well as under high<br>noise level condition caused by heavy traffic and industrial activities. In contrast, the Land Streamer<br>makes it easy to set a survey line and acquire high-quality data even in urban area because it was<br>originally developed to be utilized on a paved area and to sense SH waves instead of P wave signals<br>which are prone to be affected with ground noises. We applied it in combination with borehole logging<br>and passive surface wave method to field surveys in the Tokyo Metropolitan area. The objectives of the<br>field survey were to clarify the detailed structure in Holocene soft sediments, and to characterize them<br>based on the S-wave velocity and other physical properties. As a result, the seismic reflection surveys<br>helped to interpret the sedimentary sequence of Holocene and to assess the geotechnical properties of the<br>surface sediments in the area.