Visualization of crustal deformation in a high-strain shear zone by geodetic, geomorphologic, and geologic approaches

Niwa, Masakazu   ; Shimada, Koji   ; Watanabe, Tsuyoshi ; Goto, Akira; Hiratsuka, Shinya 

As a case study to visualize crustal deformation induced by concealed faults and related structures, we applied integrated approaches of geodesy, geomorphology, and geology to a high-strain shear zone in southern Kyushu, Japan. Our GNSS observation for recent 4.7 years by a network composed of 10 stations revealed that locking depth and slip velocity of the deeper extension of the fault were estimated to be 8 km and left-lateral slip of 9 mm/year. In the geomorphological approach, concentration of E-W trend lineaments is identified in northwestern Kagoshima, near the center of the sinistral high-strain shear zone detected by the GNSS observation. The field survey showed that minor faults are common in the study area. Thus, we analyzed stress field estimated from slip data of the minor faults, and compared it with the stress field corresponding to the sinistral high-strain shear zone. The result of the analysis suggests that the subsurface deformation due to the sinistral high-strain shear zone is localized rather than dispersed.