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

Abstract

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