地震探査から見た関東平野の基盤構造  [in Japanese] Structure of the pre-Tertialy basement beneath the Kanto Plain revealed by geophysical data  [in Japanese]

Structure of the upper crust, espccially the pre-Tertialy basement bcneath the Kanto Plain is discussed mainly based on the geophysical data-seismic, gravity and airborne magnetic data and the following conclusions are obtained (1) Five velocity layers are identified by seismic survey, (2) The fourth and fifth layers correspond to the pre-Tertialy basement Belt: geologically, the former to the Shimato Belt, the latter to the Chichibu, Sanbagawa Beft or the Inner Zone (3) The boundaries of the Sanbagawa belt is determined by the range of the high and low anomalies round commonly in the gravity and magnetic map. (4) Gap of the succession of the high and low anomalies is found in the central part of the Kanto Plain and suggests that the tectonic line named the Kashiwazaki-Tokyo Bay Tectonic Line runs through the central part of the plain and Tokyo Bay from the north to the south. (5) It is infered that the southern extension of the Tanakura Tectonic Line runs to the sea off Kashima. (6) The Kashiwazaki-Tokyo Bay tectonic line, the Itoigawa-Shizuoka Tectonic Line and the Tanakura Tectonic Lineare parallel each other and this is thought to relate to collision of the Izu-Ogasawara Arc. (7) The Kashiwazaki-Tokyo Bay Tectonic Line may be related to large earthquakes which have occured near Tokyo Bay and caused major damage in Tokyo.