Detailed Geomorphological and Geological Investigations for the Major Active Faults Carried out by Trenching

Atera断层形成了一个主断层系统，主要是左行位移分量，并已通过几次挖沟进行了研究。对比这些结果可以看出，由于各海沟的复发间隔相似，主断层将在整个地震道上与大地震同时发生位错。由于该断层具有相当复杂的断层模式，因此，通过1：25，000比例尺的照片判读，绘制了详细的断层痕迹和断层分类图。日本陆上主要活动断层的发掘研究，主要目的是揭示至少在最近几千年内每次断层活动的年龄和真实的复发间隔。最后一次史前地震的精确数据对于评估未来的地震危险性特别重要。因此，碳-14测年和考古方法被用来确定地层和事件。通过这些研究，阐明了主要活动断层，特别是Atotsugawa断层、Itoigawa-Shizuoka构造线（中部）、Middle构造线Okamura断层和Atera断层的破裂事件、复发间隔、断层的地下结构和断层行为等。详细的描述和信息与每篇论文一起发表在下面的参考文献中。东京大学出版社出版了一本名为“九州活动构造学”的综合书籍。冈田克也是这本书的主要作者。本书旨在介绍活动构造（活动断层、褶皱、区域隆升和沉降等）、以1：50，000比例尺的单张地图形式提供地貌面分类、滑坡分布和火山要素。特别是对九州的活断层作了详细的介绍，阐明了活断层的分带性、区域背景及其与地震的关系。

The Atera fault forms a master fault system with predominantly left-lateral component of displacement and has been studied by several trenchings. Comparing these results it has been clarified that the main fault would simultaneously dislocate through the whole trace with large earthquakes, as each trench has the similar recurrence interval. As this fault has rather complex fault pattern, detailed traces and classification of faults were mapped by photo-interpretation on a scale of 1:25,000.The excavation study for major active faults on land in Japan has been aimed principally at revealing ages of each event of faulting and real recurrence intervals during, at least, the last several thousand years. The precise data of the last prehistoric event are particularly important for evaluating future seismic hazard. Therefore, carbon-14 datings and archaeological methods were used to determine the strata and events. From these investigations, rupture event, recurrence interval, subsurface structure of fault and behaviors of faulting and so on were clarified for the major active faults, especially Atotsugawa fault, Itoigawa-Shizuoka Tectonic Line ( central part), Median Tectonic Line Okamura fault) and Atera fault. Detailed description and information were published with each papers listed on references below.A comprehensive book entitled with "Active Tectonics in Kyushu" was published from the University of Tokyo Press. Okada is the chief author in this. This book aims to present such data as active tectonics(active fault, folding, regional uplift and subsidence etc.), classification of the geonorphological surfaces, distribution of the landslide, and volcanic elements in the form of sheet maps on the scale of 1:50,000. Especially, this book provides detailed informations on active faults in Kyushu and clarified the zonal arrangements, regional setting and relationship to the earthquakes of active faults.