Multichannel seismic reflection profiling in the Suruga Trough.

Abstract

During January 1978, the Hydrographic Department, Maritime Safety Agency acquired approximately 94km of digitally recorded 48 channel seismic reflection data using high-pressure, large volume air guns on the R/V Takuyo-maru (Japan Petroleum Exploration Co.) on three track lines in the Suruga Trough off Sizuoka Prefecture, Japan (Figure 1, 2, 3 and Table 1). Three multichannel seismic reflection profiles, which reveal a structure of the upper crust having a depth of 11-14 km, were processed from the data using the common depth point technique with 24 folds. The authors found strata and faults from interpretation of the profiles (Figure 4), and also drew P wave velocity structure derived from velocity analysis using the common depth point technique (Table 2 and Figure 5). Especially, the authors considered fault zone along the Suruga Trough as follows : 1) The fault zone located along the west side of the Trough axis is vertical or slanted apparently westward. 2) The fault zone is possibly a reverse fault, because the Senoumi North Bank and South Bank in the western part of the fault zone are tilted blocks tilting to the west with the fault zone as a fault scarp, and strata of the eastern part of the fault zone show homocline-like structure slanting toward the Trough. 3) The strike of the fault zone shows a largely north-south trend. 4) The fault zone was formed after sedimentation of the B layer corresponding to the middle to late Tertiary (Table 3), and the tectonic movement which produced fault zone has continued until the recent period.