关键词: 安丘-莒县断裂, 驸马营, 覆盖区, 断裂特征

Abstract: The Anqiu - Juxian fault is an important seismogenic fault in the east of China, along which many strong earthquakes occurred in history. From north to south, the fault can be divided into Anqiu section, Juxian - Tancheng section and Xinyi - Sihong section. According to the space distribution, occurrence and activity characteristics of the fault, the Anqiu section also can be divided into five small sections, which are the north of Changyi section, Changyi - Nanliu section, Anqiu - Mengtuan section, Qingfengling section and Mengyan section. Since the late Quaternary, the Anqiu - Juxian fault can be divided into two branches, which are named west branch F5-1 and east branch F5-2. There is a hidden area in Fumaying village, Weifang. In order to find out the fault features of the hidden area on Anqiu - Changyi segment of the fault, the geological-geomorphological investigation, shallow artificial seismic lines, combined drillings, trenches and OSL dating test were carried out. Through this work，we obtain several understandings as follow: (1) The results of geological and geomorphological survey and shallow seismic profiles show that the Meicun - Shuangguan segment of Anqiu - Juxian fault can also be divided into F5-1 and F5-2. The branch F5-2 of the fault is hidden in the Quaternary layer, and the west branch F5-1 exposes at the east slope of the hill. Between the two branches of the fault is called as the Fumaying hidden area in this paper. In the Fumaying hidden area. (2) The combined drilling section in the Fumaying hidden area showes that the east branch F5-2 passes between the drillings Z4 and Z5, and the upper breakpoint can be inferred to extend to the interior of the layer w2 Heituhu formation of Holocene Series, buried at the depth of 4.2 ~ 6.9m. The shell was sampled as 14C dating sample at the bottom of Heituhu formation, and the result of the No. 14C-1 is (9.79 ± 0.03) ka BP, indicating that the latest active age of the east branch is the Holocene. (3) Between the two branches, a long strip-shaped Quaternary basin is formed along the east branch fault. The Quaternary at the west side of the fault developed well, and the layers of lower Pleistocene, middle Pleistocene, upper Pleistocene and Holocene can be seen in the drilling cores; Only the upper Pleistocene and Holocene deposited at the east side. This phenomenon indicates that the Fumaying basin has deposited in the early-middle Quaternary and has the characteristics of the faulted basin. (4) There are different activities in different periods between the two branches of the Anqiu - Juxian fault. The Fumaying hidden segment of the east branch F5-2 was active obviously in the early-middle Quaternary, and still active since the late Quaternary. According to the geological and geomorphological survey, there is a set of the late Pleistocene yellow silt strata was offset by the fault west branch F5-1, indicating that the latest active age of the west branch is the late Pleistocene.

Key words: Anqiu - Juxian fault, Fumaying village, hidden area, fault features