日本横手盆地东缘陆羽逆断层系的同震地表破裂特征及其分段性

COSEISMIC SURFACE RUPTURE FEATURES OF THE RIKUU REVERSE FAULT SYSTEM ALONG THE EASTERN MARGIN OF THE YOKOTE BASIN, NORTHEAST JAPAN AND ITS SEGMENTATION

通过对陆羽逆断层系上１８９６年同震地表破裂特征、长期活动习性和断错地貌等的研究，给出了可识别的逆断层型段落边界的标志，它们是断层崖形态持久性变化的过渡地段、断层抬升盘山地分水岭高程明显变化的转折部位、剖面几何结构转换区和断层下降盘盆地内的隐伏横向基岩脊等；指出逆断层上公里量级的空缺和阶区不能有效地终止或延缓逆断层型同震地表破裂的横向扩展，因此，不能作为逆断层型段落的边界，最后对陆羽逆断层系的千屋段和横手段的地震危险性进行了简要评估。

The recognizable segment boundaries of the Rukuu reverse fault system are obtained through study of coseismic surface ruptures for the 1896 Rikuu earthquake, long term faulting behaviour and offset geomorphology. They are the transition areas for permanent change of fault scarps, watershed altitudes most nearby the faults and geometrical structures of active reverse faults in cross section, and buried tranverse bedrock ridges. The stepovers and fault trace gaps in kilometers′ order can not stop or slow down effectively coseismic surface rupture propagation along the reverse fault strike, thus, can not serve as segment boundaries for reverse faults. The seismic risk on the Senya and Yokote segments of the Rikuu reverse fault system along the eastern margin of the Yokote basin is also assessed briefly.