Evaluating the activity of Holocene faults in Japan

本研究的总体目标是评估日本全新世断层的活动性，并为了解日本弧在最近的地质历史中的构造提供基本的定量数据。1995-1997年，我们使用高分辨率、大比例尺航空照片对日本弧中的代表性断层带进行了航空照片解释，以便绘制精确的几何图形并提取与全新世断层有关的变形。在全新世地貌面上发现了许多地表变形的新证据，为研究活动断裂的分段和分组问题提供了重要资料。1996年出版的《城市活动断层图》系列中，部分工作已完成。为了确定断层带的净滑动速率，需要断层带的地下几何信息以及地表变形速率。1996 ~ 1997年，在航片填图的基础上，对选定的断裂带进行了地貌、地表地质、钻探、反射地震剖面、重力等野外调查。这些综合研究表明，在评价断层在近代地质史中的整体活动性方面是有效的。

The overall objectives of this study are to evaluate the activity of Holocene faults in Japan, and to provide basic quantitative data for understanding the tectonics of the Japan arc in recent geologic past.In 1995-1997, we carried out air-photo interpretation over representative fault zones in the Japan arc using high-resolution, large-scale aerial photos, in order to map precise geometry of and to extract deformation associated with Holocene faults. As a result of this work, we found many lines of new evidence for surface deformation on Holocene geomorphic surfaces, which provide us important data for segmentation and grouping problems of active faults. Part of this mapping work has been published as "Active Fault Map of Urban Area" Series from the Geographical Survey Institute in 1996.In order to determine the rate of net slip on a fault zone, information on subsurface geometry of the fault zone, as well as the rate of surface deformation, is necessary. On the basis of air-photo mapping, we carried out field researches of geomorphology, surface geology, drilling, reflection seismic profiling, and gravity survey for selected fault zones in 1996-1997. These integrated researches have revealed to be effective in evaluating the overall activity of faults in recent geologic past.