Inland active fault earthquakes directly under the urban areas possibly cause enormous damages over a wide area mainly near the fault. In this study, we propose a method for predicting strong ground motion in the vicinity of inland active faults. Previous studies on the 2016 Kumamoto earthquake have shown that shaking near active faults were affected by long-period strong ground motions that occurred shallower than the seismogenic layer. Here we constructed fault models based on information obtained from active fault surveys after the Kumamoto Earthquake and calculated seismic motion. We compared the earthquake waveforms calculated using the fault model with those observed at seismic intensity meters around the surface ruptures, suggesting that our calculated waveforms were generally consistent with observed waveforms. The length of our fault models was shorter than those estimated in the seismic source inversion results of previous studies. Earthquake magnitude from fault model estimated from the empirical relationship between fault area and seismic moment is almost equivalent to those reported for the Kumamoto Earthquake. These results show that it is effective to use geological information such as active fault distributions to construct fault models to strong ground motion prediction. Although not all of structures of source faults can be accurately predicted from prior information, it is important to use highly precise geologic information on active faults before the earthquake to construct fault models for prediction of strong ground motion.

　 Submarine active faults are important information regarding seismic source faults such as plate-boundary mega-thrusts earthquakes and also tsunamis source faults such as the 2011 off the Pacific coast of Tohoku earthquake. However, the importance of submarine active faults in earthquake prediction is not widely recognized by researchers in the related fields. One of the reasons for this is that the reliability of geomorphological method used in the submarine active faults identification is not well understood.

　 The purpose of this study is to identify submarine active faults by using the similar geomorphological method used for land active faults, in order to clarify the distribution of submarine active faults along the plate boundary. Recent advances in seafloor exploration technology, including narrow multi-beam acoustic sounding, have made it possible to use high-resolution bathymetry model (DBM). Using anaglyph stereoscopic images created from the DBM provided by Japan Coast Guard and JAMSTEC, we mapped seafloor active faults by tectonic geomorphological methods. We demonstrated seven typical examples of submarine active faults along the trench and trough as well seafloor between land and outer ridge. We examined relation between the faults and geological structure observed on the seismic reflection profiles database published by JAMSTEC. Most of the active faults are associated with faulted and/or deformed structures observed reflection profiles.

　 In addition, following the tectonic geomorphological method, we made submarine fault map of the Nankai trough and its vicinity. We also examined relation between the faults and geological structure of the seismic reflection profiles. In the study trough area, there are 41 seismic reflection lines across 188 active faults, and their intersections are 345. Out of 345 sections, faulted structure is recognizable at 195 sections and deformed structure 130 sections. This means that 65 per cent out of active faults is associated with faulted structure and 97 per centis associated with faulted and deformed structures. This suggests that the submarine active faults identified by tectonic geomorphological method are very reliable.

　 The evaluation of active faults on the site of nuclear facilities is an important issue that should not be overlooked because it affects the lives and safety of the public. The Nuclear Regulation Authority’s External Expert Meeting on the Fracture Zone on the Site of the Prototype Fast Breeder Reactor Monju concluded in its evaluation report that the on-site ‘a’ fracture zone is not an active fault which has not been active since at least the Late Pleistocene. From the tectonic geomorphological point of view, it is highly likely that the fracture zone is an active fault continuing to the known Shiraki-Nyu fault. The report does not appropriately reflect the opinions of the experts and reviewers, and contains many fatal issues.