1948年福井地震に先だつ周辺の主要な地震によつて生じた福井地方の歪みの蓄積について

抄録

The fault parameters of earthquakes in the Japan area (1926-1948) are referred to, and their contribution to strain accumulation is computed in the Fukui area, Honshu, Japan, where a big earthquake occurred in 1948 (M=7.3, 136.2°E, 36.1°N, depth about 20km, after JMA). Taking the focal mechanism of the Fukui earthquake (strike-slip type) into consideration, the discussion is developed with respect to the increase or decrease of the strain component, ε_YY-ε_XX, which would play an essential role in the present faulting.
Especially remarkable is the contribution by several major shocks, such as the Tottori (1943), the Tonankai (1944), and the Nankai (1946) earthquakes, which immediately preceded the present event and resulted in significant increase of the strain component. Quantitatively, the present effect may cause the changes of 6×10^-7 in strain, and 200mb in stress, approximately. It is questionable that small disturbances of this magnitude can be a definitive trigger, always. In some critical cases, however, a fractional change in strain or stress may play an essential role. Further knowledges about the present effect are needed for better understanding of the focal processes.