Abstract
We analyzed the profiles of the ground-penetrating radar (GPR) performed before the trenching study across the Gero fault in the Atera fault system, and reviewed the reflection pattern of subsurface structure around the active fault. The GPR profile eliminated fake images by the migration process have enabled to interpret the reflection pattern more exactly. Comparing the GPR profile with the trench wall in the Mimayano site, it was proved that the active fault is detected as a sheared reflection or a linear gap. Besides, it was able to detect the sedimentary structure of the depression formed between two faults through the indeterminable depth by trench. Thus, GPR survey can detect the active fault in this area, and it is available for the method to get the additional information of trenching study.
The GPR profile performed above the outcrop of the Atera fault showed the geologic structure clearly, however, the active fault could not be detected according to a few snow cover of surface and anomalous landform of outcrop.
In the Norimasa site, where is able to estimate the place of the Gero fault from a landform, the GPR profiles showed a sheared reflection same as the Mimayano site at the estimated place. Besides, a complex structure confused from a landform was presumed from the profiles. The GPR survey is effective method to elucidate the subsurface structure around an active fault and support with trenching study.
