Earthquake surface rupture appears not only along the principal fault that caused the earthquake but also pre-existing other faults or folds nearby. Although surface ruptures along subsidiary structures are often small and discontinuous, given its extensive occurrence, comprehensive mapping of active faults and folds is necessary for understating strain distribution within a fault zone to evaluate fault displacement hazards. The Nagamachi-Rifu line fault zone, consisting of sub-parallel reverse faults, runs across Sendai City, and recent studies suggest that there are several active structures not shown on existing active fault maps. However, it is difficult to obtain their convincing geomorphic evidence because their surface deformation is subtle and is easily obscured by erosion and artificial modification. To reevaluate active faults and folds of the fault zone, we studied shallow geologic structure across the fault zone using a borehole dataset and conducted a geomorphological analysis using 2 m DEM. Our results indicate that the fault surface of the Nagamachi-Rifu line does not reach the surface causing flexural deformation at the surface rather than brittle deformation, as the previous studies pointed out based on seismic reflection surveys. We also found that the deformation zone of the Dainenjiyama fault is broader than previously thought. This is probably because its fault scarp retreated by hundreds of meters due to erosion. To the northwest of the Dainenjiyama fault, there is an NNE-SSW trending zone where the base of the Quaternary deposit was elevated compared to its surroundings, which may correspond to the previously estimated active anticline. The ratio of vertical displacement of the Nagamachi-Rifu line, Dainenjiyama fault, and the anticline is estimated to be 5-6: 3: 1. We could not newly find other faults or folds, including those exposed at outcrops reported in previous studies, suggesting that there are several active structures of which cumulative displacement is too small to be observed in our analysis. Nonetheless, a shallow geologic structure revealed from a borehole dataset, coupled with detailed topographic analysis, can help to locate active structures with minor surface expression and evaluate seismic hazards.

　 The active Sakota-Ikumo and Tokusa-Jifuku faults of the Lake Ohara-W. Yauneyama fault system extending in northeast-southwest direction are distributed in parallel in northeastern Yamaguchi Prefecture. The ENE-WSWtrending Chomonkyo fault belonging to the fault system is situated at a section, from Nakanotoro, Kawakami, Hagi City to Watarigawa, Ato-Ikumo-Higashibun, Yamaguchi City, between the two active faults, and has been pointed out to be active because it is accompanied by valleys and ridges bending to the right, but the timing of its movement remains unknown. We conducted an outcrop exploration, and paleoseismic trench and boring surveys to clarify the timing of paleoearthquakes.

　 We found an outcrop of the Chomonkyo fault, which strikes ENE-WSW and dips nearly vertical, cutting unconsolidated sediment layers. The fault is accompanied by a fault zone consisting of cataclasite and fault gouge, and approximately horizontal slickenlines can be recognized on the fault plane. We suggest that the motion sense of the fault changed from sinistral to dextral because the cataclasite and the fault gouge have composite planar fabrics indicating sinistral and dextral strike-slip faultings, respectively.

　 The trench and boring surveys conducted near the active-fault outcrop indicated that the Chomonkyo fault slipped twice after 4.5 ka and also at least twice between 130 and 6.8 ka. Therefore, it is possible that a recurrence interval of the fault before 6.8 ka is longer than that after 4.5 ka. However, it is more probable that a recurrence interval of the fault after 130 ka is constant because the fault may have slipped significantly more than twice between 130 and 6.8 ka.

　 The Tokamachi Fault Zone (TFZ) and the Nagano Basin Western Margin Fault Zone (NBWMFZ) are active fault zones located in the middle part of Honshu Island. These two fault zones are distributed subparallel, and the southeastern end of the TFZ and the northwestern end of the NBWMFZ are separated by about 20 km. To discuss the continuity of these two fault zones, we mapped short active faults distributed in the gap between the TFZ and the NBWMFZ, measured the vertical offsets, and estimated the vertical slip rates. These active faults consist of WNW-ESE trending short (less than several kilometers) faults distributed subparallel to each other, and they are interpreted as normal faults, considering their linear fault traces. These faults consist of the Busuno-toge Fault Group, the Nonomi-toge Fault Group, the Hirataki Fault, and the Akasawa Fault Group. The Akasawa Fault Group has displaced the Maibara Terrace by <9 m, and vertical slip rates were estimated to be <0.04 mm/yr. These slip rates are two orders of magnitude smaller than these of the TFZ and the NBWMFZ. Based on distribution pattern, deformation style, and slip rates of faults, we interpreted that these short active faults have been formed indirectly by activities of blind right-lateral slip fault located between the TFZ and the NBWMFZ. This interpretation indicates that the TFZ and the NBWMFZ may have a continuous structure, or that the southwestern end of the TFZ may extend to near the western end of the Busuno-toge Faults.

　 The Futagawa fault, extending southwest from Aso caldera, is one of the major dextral strike-slip active faults in Kyushu, southwest Japan. On 16 April 2016, the Kumamoto earthquake (Mj 7.3) occurred, and ~31-km-long right-lateral surface ruptures appeared along the Futagawa fault. After the 2016 earthquake, several trenching surveys were conducted across surface ruptures to reveal the faulting history. However, no trenching survey has been carried out in the 15-km-long middle section from Dozon to Aso caldera. We conducted a trenching survey and an additional hand auger survey to reveal faulting history in Komori, Nishihara Village, in the middle of the section. Furthermore, we carried out a geomorphological survey for the detailed description of the surface ruptures around the trench site.

　 At the trench site, a ~40-cm-deep graben was formed by the 2016 earthquake. A similar graben structure appeared on the trench wall units, which shows larger vertical deformation than that of the 2016 earthquake, indicating that similar types of deformation to the 2016 earthquake have repeatedly occurred at this site. Based on such deformational features of units, we identified at least four faulting events, including the 2016 earthquake, since about 11,500 cal BP. Also, the timing of the penultimate event was 2,240-1,910 cal BP and the calculated recurrence interval was 2,400-3,800 years. The penultimate event may have been simultaneous in the section from the northeastern part of the Aso caldera to the southwestern part of the fault zone, similar to the 2016 Kumamoto earthquake. If this idea is correct, based on the overlap among event dates from previous studies as well as our result, the timing of the preceding earthquake is about 2,000 cal BP.

　 In this study, the author attempted to estimate trace of the northern concealed section of the Isurugi Fault, classified as a part of the western part of the Tonamiheiya Fault zone in Toyama Prefecture, central Japan, by examining stratigraphic columnar sections obtained from existing borehole log data. The results showed that, based on the lateral continuities of significant vertical differences in presumably identical sediments recorded in the borehole log data, the main part of the Isurugi Fault appears to extend northeast along the lower part of the Oyabe River, reaching Toyama Bay via the central part of Takaoka City. The total length on land of this fault was found to be about 30 km. Borehole log data thus appear to be potentially useful for estimating traces of a concealed active faults.

　 Geoparks are UNESCO programs that promote sustainable development of areas with geologically valuable sites and landscapes through conservation, education, and geo-tourism activities. One of the characteristics of Japanese geoparks is that the entire Japanese Islands are located in the mobile belt, and many geoparks have the theme of “Dynamic Earth.” Active faults, along with active volcanoes, symbolize the movements of the ground in the Japanese Islands, and it is of great significance for researchers of active faults to support geopark activities. In the present study, we reported the results of the questionnaire survey conducted by the Committee on Education and Outreach of the Japanese Society for Active Fault Studies to consider future policies for support for Japanese geoparks. As a result, we found that about 41% of the geoparks use active faults as geosites, and about 62% of the geoparks explain active faults in some way. In addition, it was found that about 81% of the geoparks have been working on disaster prevention against earthquakes or active faults. On the other hand, there are some geoparks where active faults are distributed within the area but are not utilized as geosites, and the most common reason for this is that there are no appropriate observation sites. For these geoparks, support by experts of active faults is considered necessary.