西南日本内陸の活断層に発生する深部低周波地震

Abstract

西南日本には, 深部低周波地震が発生する内陸活断層系が存在する.鳥取県西部地域のほか, 数ヶ所で同様の観測例があり, これらの地域には下部地殻から上部マントル領域に地震波の低速度領域が存在する.これは, 断層深部の流体の存在を示唆しており, 地震発生に至る過程の解明に重要な知見を与える観測例となるだろう.

There are several examples of DLF's that are associated with active faults in southwest Japan.Seismic tomography analysis indicates the existence of a low-velocity body at depths from the lower-crust to the upper-mantle in the focal region of these DLF's. The distribution of DLF activities corresponds well to the low-velocity region rather than to the distribution of volcanoes.The DLF occurrences are probably direct evidence of fluid activity in the seismogenic zone, which might be injected from thelower-crust beneath active faults.