西南日本の巨大地震発生様式についての一仮説

概要

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It is well known that great earthquakes have occurred repeatedly along the Nankai trough in Southwest Japan. The eastern half of the source area of the 1707 Hoei earthquake ruptured again during the 1946 Nankaido earthquake, while the western half area ruptured at the time of the 1944 Tonankai earthquake. From this, it may be inferred that one earthquake could rupture the entire source area in these regions and another only a half of it. In this paper, I suppose a simple 2-dimensional crack model in which some barriers divide a fault plane into two parts, and the fracture strength of one part is lower than that of another. If the rupture starts in the high strength part, then the whole fault plane can be ruptured. If the rupture starts in the point of the low strength part, then the rupture cannot propagate toward the high strength area and only a half of the fault plane is ruptured.
1982-07-16