Evaluation of fault activity along the major active fault zone based on new and detail fault data

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The location of active faults is one of the most important data for large seismic activities in the past, earthquake prediction on land and the relevant seismic hazard mitigation. Even in an earthquake country Japan, danger of active faults was not well understood among the people before 1995 Kobe earthquake. In order to provide the fundamental information regarding active faults such as their distribution and characteristic activities, we have re-interpreted air-photographs in Japan and depicted the detailed location of active fault traces together with related information. We defined active faults as faults that have repeatedly moved during the late Quaternary with intervals of one thousand to ten thousand years forming distinctively fault-related tectonic features on the surface.In 2002, "Atlas of Quaternary Thrust Faults in Japan" and "Digital Active Faults Map of Japan" were published in the scale of 1:25,000. These maps provide us with detailed information regarding their location and characteristic of fault activities for basic data of other science fields and seismic hazard mitigation. It is, however, important to know that criteria as "active" for the active faults and aims for compilation of the maps vary each other as well as from previously published maps.We need to study further problems and questions concerning the characteristics of active faults and the mechanism of the occurring of earthquake ;1) whether the recurrence interval of faulting has been uniform over time or not ;2) whether or not each fault has a characteristic distribution of the amount of displacement ;3) how many segments divide a long active fault or how many faults group in a particular earthquake ;4) how we can distinguish between the main fault and the subsidiary faultand how active faults on the surface related to underground seismogenic faults through the investigation of seismic reflection profiles and their geological data.