地震地质 ›› 2015, Vol. 37 ›› Issue (1): 176-191.DOI: 10.3969/j.issn.0253-4967.2015.14

• 研究论文 • 上一篇    下一篇

安丘-莒县断裂北段几何结构与最新活动特征

王志才, 王冬雷, 许洪泰, 葛孚刚, 杨传成, 李建虎   

  1. 山东省地震局, 山东省地震工程研究院, 济南 250014
  • 收稿日期:2013-12-19 修回日期:2014-09-22 发布日期:2015-05-15
  • 作者简介:王志才,男,1966年生,2004年在中国地震局地质研究所获构造地质专业博士学位,研究员,主要从事活动构造、新生代构造研究,E-mail:wzc11851@163.com。
  • 基金资助:

    山东省自然科学基金(ZR2012DM005)和中国地震局地震行业科研专项(200908001)共同资助

GEOMETRIC FEATURES AND LATEST ACTIVITIES OF THE NORTH SEGMENT OF THE ANQIU-JUXIAN FAULT

WANG Zhi-cai, WANG Dong-lei, XU Hong-tai, GE Fu-gang, YANG Chuan-cheng, LI Jian-hu   

  1. Earthquake Administration of Shandong Province, Jinan 250014, China
  • Received:2013-12-19 Revised:2014-09-22 Published:2015-05-15

摘要:

安丘-莒县断裂是沂沭断裂带的主要分支之一, 也是最主要的一条活动断裂。通过断裂活动性调查和地质填图, 查明了安丘-莒县断裂北段的空间展布、几何结构以及最新活动特征。在莒县至昌邑一带, 安丘-莒县断裂自北向南大致可划分为昌邑—南流段、安丘—孟疃段、青峰岭段和孟堰段等4个段落。它们以左阶斜列形式展布, 而每个断层段又由更次一级的段落以右阶斜列的形式组成。昌邑—南流断层段的最新活动时代为全新世中晚期, 除右旋走滑断层活动外, 还观察到逆冲和正断运动分量, 其中正断运动分量的发生时代较新。安丘—孟疃和青峰岭2个断层段以右旋走滑运动为主, 兼有逆冲运动分量, 最新活动时代分别为晚更新世和全新世早期。孟堰断层段也以右旋为主兼具逆冲分量, 最新活动时代为全新世早期。安丘—孟疃断层段公元前70年曾发生过安丘7级地震, 结合断层活动性质和最新活动时代综合判断, 山东莒县以北的安丘-莒县断裂的未来地震危险性较大, 在今后的地震灾害防御和地震预测工作中应予以重视。

关键词: 活断层分段, 安丘-莒县断裂, 安丘7级地震

Abstract:

The Anqiu-Juxian Fault is a major branch fault and an active prominent fault of the Yishu Fault belt. The spatial distribution, geometric features and the latest activities of the Anqiu-Juxian Fault are studied by field survey and mapping in this study. The northern segment of the Anqiu-Juxian Fault between Juxian and Changyi can be divided into four segments, namely from north to south, the Changyi-Nanliu segment, the Anqiu-Mengtuan segment, the Qingfengling segment and the Mengyan segment. These segments are left-step en echelon arranged, and each of the fault segments consists of right-step en echelon arranged sub-segments. The Changyi-Nanliu segment is about 31km long and composed of 4 sub-segments in right-step en-echelon arrangement, namely, Wenshan sub-segment, Zhuli sub-segment, Shuangguan-Meicun sub-segment and Nanliu sub-segment, from north to south. The length of these sub-segments is 5km, 7km, 10km and 9km, respectively. The width of the stepover between them is about 2~3km. The Changyi-Nanliu segment generally strikes~15°, and the fault plane dips both west and east with dip angle 70°~80°. This segment offsets the widely distributed eolian yellow or orange fine sand and silt that were formed in the latest late Pleistocene, and it also offsets the mid-Holocene grey-yellow clay. The latest active age of the Changyi-Nanliu segment is the middle and late Holocene. This segment is characterized by right-lateral strike-slip motion with thrust and normal fault component, and the normal faulting activity is usually younger than the reverse faulting activity. The Anqiu-Mengtuan segment is about 50km long and exposes~21km. It strikes 15°~20°with the major fault plane dipping NWW with dip angle 70°~80°. This fault segment is characterized by right-lateral strike-slip motion with west-to-east thrust component. The segment can also be divided into two sub-segments, namely, the 13km long Anqiu-Guangong sub-segment and the 8km long Anshang-Mengtuan sub-segment, as in right-step en echelon arrangement, with a stepover of about 3km in width. The youngest offset stratum along the Anqiu-Mengtuan segment is the late Pleistocene, so, its latest active age is the late Paleocene and early Holocene. The Qingfengling segment is about 32km long, striking 15°~20°, dipping mainly southeast and partly west with dip angles more than 60° generally. This segment is characterized by right-lateral strike-slip motion with minor thrust component. It is composed of 4 sub-segments, which are the Xiaodianzi-Henhushan sub-segment, Kushan-Chezhuang, Maobu and Wangtaizi sub-segment, respectively from north to south. The length of these sub-segments is 6km, 8km, 14km and 4km, respectively. The former three sub-segments are aligned right-laterally. The Qingfengling segment offsets the upper late Pleistocene and the early Holocene strata; its latest active age is the early Holocene. The Mengyan segment exposes about 20km, striking 20° and dipping northwest with dip angle ~70°. It is also characterized by right-lateral strike-slip motion with thrust component, and its latest active age is the early Holocene.
The only historical earthquake that occurred on the north segment of the Anqiu-Juxian Fault between Juxian and Changyi is the 70BC Anqiu M7 earthquake. However, paleo-earthquake researches show that several strong earthquakes occurred along the Qingfengling segment and the Mengyan segment between the latest late Pleistocene to early Holocene. The time of the latest strong earthquake is ~3 500a BP, 2 084a BP (-70BC), ~10 000a BP, ~10 000a BP on the Changyi-Nanliu segment, Anqiu-Mengtan segment, Qingfengling segment, and Mengyan segment, respectively. Since the strong earthquake recurrence interval is still not known for each segment, the exact time for the next strong earthquake can't be predicted. However, according to the geometric features, latest active age, latest activity features, historic earthquake data and paleoearthquake documents of this active fault, the 4 segments do have seismotectonic conditions for generating M≥7 earthquake, and the potential earthquake risk does exist and may be rather high and imperative. Thus, the fault activities and the potential earthquake hazard should be considered during future earthquake hazard prevention and prediction.

Key words: active fault segmentation, Anqiu-Juxian Fault, Anqiu M7 earthquake

中图分类号: