関東地方の震源分布と地質構造

概要

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Relatively large earthquakes have occurred under the flexure zones which correspond nearly to the outer edges of such highlands as Musashino and Shimosa. Dest ructive earthquakes show the similar distribution. Faults planes deduced from the P-wave radiation pattern of earthquakes occurred not only in the crust but in upper mantle run nearly parallel to those flexure zones. It might be due to the fact that each tectonic unit bounded by the flexures spreads its root deeply into the upper mantle vertically. Though the general trend of geologic structures is east-west in south Kanto district, the fault planes deduced from the P-wave radiation pattern meet nearly perpendicular to it. It might becaused by the fact that the geologic structures with east-west trend are shallow but those with north-south strike are deep in their roots. The subsidence of the Kanto plain is now in progress where the deep earthquakes take place very often, and relatively deeper earthquakes happen near the center of subsidence, so the earthquakes are regarded as the deep process of the movement.
日本地質学会の論文
1981-03-30