Studies on the Bouguer anomaly of active faults along the western margin of the Kanto plain

利用LaCoste和Romberg重力仪在东京大都市区西部约1700平方公里的区域内约1500个站点进行了重力观测，目的是澄清那里的断层结构。得出以下结论：(1)本次调查新发现的玉玉断裂、钏木断裂和Kasukawa断裂连续出现在一条断裂线上。1931年的西埼玉地震可能是由这些断层的联合运动引起的。(2)从地形学角度来看，立川断裂是一条向西南方向沉降的垂直断裂，但目前的重力测量结果表明，该断裂可能是一条包含垂直位移的左旋走滑断裂。

Gravity observations were made at about 1,500 stations with a LaCoste and Romberg gravimeter over an area of about 1,700 km_2 in the western part of the Tokyo metropolisphere for the purpose of clarifying fault structure there. Our conclusion is as follows:(1) The Kodama fault (newly discovered by the present survey), the Kushibiki fault and the Kasukawa fault stand continuously in a single fault-line. The 1931 Nishi-Saitama earthquake may have been caused by a joint motion of these faults.(2) From the topographical point of view the Tachikawa fault is considered to be a vertical fault subsiding southwestward the present gravity survey concludes, however, that this fault may possibly be a left-lateral strike-slip fault including vertical displacements.