Abstract:

Running diagonally across the urban area of Xuzhou, the Feihuanghe(the abandoned Yellow River)Fault starts from Jiahezhai in the northwest, extending southeastwards through Sushantou, Xuzhou City and Liangtang along the abandoned Yellow River till the north of Wangji Town of Suining County, striking NWW, dipping SW, with a total length of about 70 kilometers. It is a buried fault, crosscutting Xuzhou-arc structure. There are significant topographic features indicating the existence of the fault on the earth's surface, which are clearly displayed in remote sensing images. There have been no devastating earthquakes occurring along the fault since the recorded history.
Feihuanghe Fault is one of the target faults of the project "Urban active fault exploration and seismic risk assessment in Xuzhou City". Few researches have been done on this fault in the past. The previous analysis assumes that the fault is a sinistral transtensional fault with extensional faulting in the Xuzhou-Suzhou arcuate structure at first and transtensional faulting of the Neocathaysian system later.
Based on field geological survey, shallow seismic exploration and composite drilling section method, Quaternary activities of Feihuanghe Fault are analyzed. Shallow seismic exploration results show that the Feihuanghe Fault is composed of a NE-trending south branch and a SW-trending north branch, forming a graben structure with the width of 1～2km. All breakpoints of the Feihuanghe Fault on the seismic exploration profiles show that only the bedrock surface was dislocated, not the interior strata of the Quaternary. The composite drilling profiling results show that Feihuanghe Fault has dislocated the strata of Mid Pleistocene, but not the top surface of Mid Pleistocene. Furthermore, we discovered a secondary fault of Feihuanghe Fault exposed at Fengshan Hill, and its latest activity date is the mid period of Mid-Pleistocene inferred from the cementation degree of gouge, dating results and geomorphic features. Combining the above results, we conclude that Feihuanghe Fault is of sinistral strike-slip in the early stage, and extensional faulting since the Quaternary, and the latest activity date is the middle period of Mid Pleistocene. Controlled by the tectonic setting, the activities of the NW-trending faults in Xuzhou area are significantly weaker than that of the NW-trending fault in adjacent southwest Shandong.

Key words: Feihuanghe Fault, Quaternary activities, shallow seismic exploration, composite drilling section, Xuzhou

摘要：

通过野外地质调查、浅层地震勘探和钻孔联合剖面探测等方法, 对废黄河断裂的第四纪活动性进行了研究。浅层地震勘探结果表明, 废黄河断裂由南北两条主干断裂组成, 南支断裂倾向NE, 北支断裂倾向SW, 总体为一地堑形式, 断裂宽度为1～2km。在地震剖面上, 废黄河断裂的各个断点都是以断错基岩面为特征, 并未断错第四系内部层位。钻孔联合剖面探测结果显示, 废黄河断裂断错了中更新统层位, 但未断错其顶面。在凤山一带发现1条废黄河断裂的次级断层出露, 结合断层泥胶结程度、测年结果和地貌特征等判断, 该断层最新活动为中更新世中期。综合以上研究工作成果, 判断废黄河断裂早期为左旋活动, 第四纪以来表现为张性活动, 其最新活动时代为中更新世中期。受构造背景的控制, 徐州地区发育的NW向断裂明显较相邻的鲁西南地区的NW向断裂活动性弱。

关键词: 废黄河断裂, 第四纪活动性, 浅层地震勘探, 钻孔联合剖面, 徐州