[SSS12-P08] Subsurface Structure at the North of the Yokosuka Fault by Seismic Reflection Survey
Keywords:Yokosuka Fault, fault, seismic reflection survey
Not only the survey at the north of the Yokosuka Fault (GS-NSO2) but also the other survey at the south east extension of the Takahama Fault (GS-NSO1) were carried out from September 27 to October 2 in 2018. The length of the survey line GS-NSO2 is 1810m. We used one EnviroVibe manufactured by IVI. Sweep frequency is 10 to 120Hz, and sweep duration is 16S. Standard shot interval is 5m, and exceptionally 2.5m. Total shot points are 421, and we shot 3 to 5 times for each point. We used 3 string geophones of OMNI-2400 (f0=15Hz) by Geospace. We used offline seismic recorder GSX system also by Geospace. Receiver interval is 5m, and total receiver points are 342. We made seismic profile by CMP stack.
We cannot see any obvious faults or signs related to the faults in the profile. Trenching survey indicate that the Mikawa Earthquake was preceded by one earthquake 2000 years ago. Total displacement of the Mikawa Earthquake and the preceding event is not more than 2m. It is impossible to detect the displacement in case of 2m displacement. However, it is possible in case that the displacement increase with depth. At least, we cannot detect the cumulative displacement in the survey.