ABSTRACT
Seismic reflection survey is used as an effective method to evaluate the activity of submarine active faults. By combining sediment core samples, activity intervals and average displacement rate are clarified with accuracy comparable to that of onshore trench survey. However, seismic reflection survey sees the underground information as a two-dimensional profile in the vertical direction. So, it is difficult to detect the displacement of strike-slip fault as compared with the normal fault or the reverse fault. The authors have been studying the detection of horizontal displacement at high density of high- resolution geologic exploration using sub bottom profiler at the Yatsushiro-sea which located southwest section of Hinagu fault zone in western part of Kyushu. In this paper, we consider the geological structure of this area by using the data obtained so far. Also, in the 2016 Kumamoto earthquake, a part of the fault zone was active, and an earthquake of Mw 7.0 scale occurred, and the epicenter distribution expanded in the NE-SW direction. In addition to these aftershocks, surface deformation is observed along with the main shock. As a result of comparing such observed data with the data obtained by exploration of the marine area and examining the relationship, although there is a difference in scale between the two structures, morphological similarity is recognized.
