5:15 PM - 6:45 PM
[SSS11-P01] Shallow seismic reflection survey across the Oritsume fault, Northeast Japan
Keywords:Shallow seismic reflection survey, Oritsume fault, Tectonic inversion, Active fault
The Oritsume fault distributed from Southern-east part of Aomiri prefecture to northern part of Iwate prefecture, and its length has a maximum 47 km. According to Aomori prefecture (1997), the vertical displacement rate of the Oritsume fault in the Tatsunokuchi flexure in the northern part from Mabechi River has been determined from the vertical deformation of Pliocene Togawa Formation and its age, but the late Quaternary activity of the fault is not clear.
To reveal the subsurface geological structure and its tectonic evolution, a shallow p-wave seismic survey across the Oritsume fault in Yamauchi, Karumai town, Iwate prefecture, was conducted in August 2023. The seismic line across three geological faults with north-northwest to south-southwest strike (Tsujino et al. 2018), the easternmost of which is correspond with the estimated active fault trace of Nakata and Imaizumi eds. (2002). The length of the seismic line is ca. 2.4 km with both 10 m receiver and shot interval. The source used in this seismic survey was IVI mini-viberator (T-15000). Sweep length was 16 sec and frequency range beginning at 10 up to 120 Hz. The GS11-D and GS11-3s receiver (natural frequency 4.5 Hz, Geospace Inc.) was used and 243-ch of fixed spread was adopted in this survey. We used GSR stand-alone recording system (Geospace Inc.) with 1 msec sampling rate.
The seismic reflection data was processed using the standard common mid-point (CMP) method. The CMP spacing was 5 m. The processed seismic image shows west-dipping geological faults and active fault, which is interpreted as subsurface geological structures related to the tectonic inversion.
References:
Tsujino et al., Geology of Ichinohe district. Quadrangle Series, 1:50,000, Geological Survey of Japan, AIST, 161p, 2018.
Nakata and Imaizumi eds., Digital active fault map of Japan, DVD and 60pp., Univ of Tokyo Press, 2002.
To reveal the subsurface geological structure and its tectonic evolution, a shallow p-wave seismic survey across the Oritsume fault in Yamauchi, Karumai town, Iwate prefecture, was conducted in August 2023. The seismic line across three geological faults with north-northwest to south-southwest strike (Tsujino et al. 2018), the easternmost of which is correspond with the estimated active fault trace of Nakata and Imaizumi eds. (2002). The length of the seismic line is ca. 2.4 km with both 10 m receiver and shot interval. The source used in this seismic survey was IVI mini-viberator (T-15000). Sweep length was 16 sec and frequency range beginning at 10 up to 120 Hz. The GS11-D and GS11-3s receiver (natural frequency 4.5 Hz, Geospace Inc.) was used and 243-ch of fixed spread was adopted in this survey. We used GSR stand-alone recording system (Geospace Inc.) with 1 msec sampling rate.
The seismic reflection data was processed using the standard common mid-point (CMP) method. The CMP spacing was 5 m. The processed seismic image shows west-dipping geological faults and active fault, which is interpreted as subsurface geological structures related to the tectonic inversion.
References:
Tsujino et al., Geology of Ichinohe district. Quadrangle Series, 1:50,000, Geological Survey of Japan, AIST, 161p, 2018.
Nakata and Imaizumi eds., Digital active fault map of Japan, DVD and 60pp., Univ of Tokyo Press, 2002.