The eastern marginal fault of the Nara basin consists of east-dipping reverse faults running along the topographic boundaries between the eastern hills and mountains and western basins from the southeastern rim of the Kyoto basin to the southeastern rim of the Nara basin. We conducted an ultra-rapid stacking ground penetrating radar survey across the Obitoke fault, the westernmost active fault in the Nara basin, at Imaichi-cho, Nara City. By combining the GPR data with previous borehole data, we tried to image subsurface deformation by the Obitoke fault. The ultra-rapid stacking ground penetrating radar improves the signal-to-noise ratio and the exploration depth by greatly increasing the number of stacks. The survey allowed us to obtain cross sections down to a depth of about 30 m, and we identified west-dipping monoclinal deformation due to the reverse faulting on the Obitoke fault. The results indicate that the Obitoke fault has been active since the middle or late Pleistocene. One problem with ultra-rapid stacking is that clutter caused by artificial structures on the ground is strongly apparent in the images. In this exploration, some clutters made it impossible to interpret the geological structures. Therefore, the development of methods and techniques to reduce clutter is required to obtain high-quality cross sections of ultra-rapid stacking ground penetrating radar.

　 The hinge line, formed by the accumulation of uplift associated with earthquakes in plate subduction zones, appears as a depression at the inland edge of the deformation zones. In eastern Kanagawa Prefecture, the Hadano-Yokohama tectonic line is considered a hinge line formed by the subduction of the Philippine Sea Plate at the Sagami Trough. This study analyzes gravity anomaly data to estimate the subsurface structure around the hinge line in eastern Kanagawa Prefecture. Using Bouguer anomaly data, which applied upward continuation filtering, we extracted signal components attributed to density structures at depths of 30-400 m. The signal components in the study area are approximately －1.2 to ＋2.6 mgal. The general structure of the signal is a positive gravity anomaly with a maximum value exceeding ＋2 mgal west of the Sagami River. On the other hand, in the east of the Sagami River, positive gravity anomalies are observed in the northern and southern areas, and negative gravity anomalies in the central region. The estimated density boundary surface ranges from －30 to －300 m in elevation, with a synclinal structure along an east-west axis in the east of the Sagami River. Additionally, a sudden change in the depth of density boundary surface was discovered beneath the alluvial lowlands in the Chigasaki-Fujisawa area, suggesting the possibility of an active structure. These findings contribute to understanding the complex tectonics of the region and provide insights into the relationship between the Sagami Trough’s subduction process and crustal deformation patterns.