音波探査断面から見た東京湾の地下構造  [in Japanese] Geological structure beneath Tokyo Bay by the multi-channel seismic profiling  [in Japanese]

A multi-channel seismic reflection survey in Tokyo Bay was carried out along 6 lines of 130 km in total length by the Hydrographic Department on March 1982. For this survey, two 500 cubic inches air guns as sonic sources and a 24 channel streamer cable of 1200 m length as a receiver were used. Field data were processed by the methods of CDP stacking, velocity analysis, time migration, depth conversion, and others. After these procession, a 12-fold stack section, a migrated time section and a migrated depth section for each line were made. On these sections we can clearly find the geological structure beneath Tokyo Bay to about 3 km depth. The geological structure of Tokyo Bay is summarized as follows; i) Pre-Neogene basement rock in the Kanto area is found at 2-3 km depth at the center of the bay. ii) Neogene and Quaternary layers of 2-3.4 km thick cover the pre-Neogene basement. The area of the maximum thickness of the layers moves from the southern to northeastern part of the bay. iii) A fault with strike of N50-55°W found at the northern part of the bay displaces the pre-Neogene basement down to 420 m on the north.