関東地方における大地震と小地震の震度分布の比較 : 埼玉県を例にして The distribution of seismic intensity of destructive and local earthquakes in Saitama Prefecture, central Japan
The writers and their collaborators have made study on the distribution of seismic intensity in Kanto district. They inquire of a few thousand persons the intensity who live in the wooden houses with second story. The data on the intensity are collected so on after an earthquake occurs. In this paper, following earthquakes are refferred, i.e. local earthquakes of western Tokyo (1979) and east-off Chiba Prefecture (1979); destructive ones of Kanto (1923) and Nishi-Saitama (1931). Approximate location and magnitude of those earthquakes are as follows; [Table] The distribution of seismic intensity of those earthquakes hows that straight, long and narrow zones are severe or sensitive to the earthquakes which are named the abnormalous seismic vibrated zones (F. Tsunoda, 1980). For instance, violent motion was felt along the margins of diluvial uplandand fault zones in the Kanto mountainland in case of the western Tokyo earthquake. Similar distribution was shown in the destructive Nishi-Saitama earthquake. Severe vibrated zone was found along the northeast coast of Tokyo Bay in case of the east-off Chiba Prefecture. Similar irregular distribution of intensity is found in the Kanto earthquake. Most of those anormalous seismic vibrated zones runs in northwest-southeast direction which is the general trend of the basement complex of Kanto Plain, and under some of them, faults of the basement complex are found, for instance, the Ayasegawa fault. So it must be intimately related with the faults developed in the basement. While some zones such as the Iwatsuki-Kasukabe abnormalous seismic vibrated zone run in northeast-southwest direction. The geological meaning of these zones is left to be solved in future. As already pointed out, the shock is also severe in the area where thick peat is deposited.
地質学論集 (20), 21-45, 1981