杜方^1,,
闻学泽^2,,,
冯建刚³,
梁明剑^1,2,
龙锋¹,
吴江¹
1. 四川省地震局, 成都 610041
2. 中国地震局地质研究所, 地震动力学国家重点实验室, 北京 100029
3. 甘肃省地震局, 兰州 730000

基金项目: 地震行业科研专项经费项目（20140823）资助


详细信息

作者简介: 杜方, 女, 研究员, 主要从事地壳形变与地震预测研究.E-mail:1289991429@qq.com

通讯作者: 闻学泽, 男, 研究员, 主要从事地震地质与活动断裂中-长期地震危险性研究.E-mail:wenxueze@ies.ac.cn

中图分类号: P315

收稿日期:2017-03-28
修回日期:2017-05-11
上线日期:2018-02-05

Seismo-tectonics and seismic potential of the Liupanshan fault zone (LPSFZ), China

DU Fang^1,,
WEN XueZe^2,,,
FENG JianGang³,
LIANG MingJian^1,2,
LONG Feng¹,
WU Jiang¹
1. Earthquake Administration of Sichuan Province, Chengdu 610041, China
2. State Key Laboratory of Earthquake Dynamics, Institute of Geology, China Earthquake Administration, Beijing 100029, China
3. Earthquake Administration of Gansu Province, Lanzhou 730000, China


More Information

Corresponding author: WEN XueZe,E-mail:wenxueze@ies.ac.cn

MSC: P315

--> Received Date: 28 March 2017
Revised Date: 11 May 2017
Available Online: 05 February 2018


摘要
摘要:集成活动构造与震源机制解、重新定位小震分布、历史与现今地震、GPS速度场等资料，综合分析了六盘山断裂带的构造动力学条件与变形方式、横剖面构造、历史强震破裂背景、GPS形变以及现代地震活动性，进而探讨了该断裂带的强震危险背景.结果表明：NNW向六盘山断裂带的运动与变形主要缘于青藏地块东北缘的向东水平挤出受到相对稳定的华北地块西缘（鄂尔多斯地块）阻挡而聚集的水平挤压作用；此外，海原和陇县-宝鸡两条NW向走滑断裂带的左旋运动在右阶区的局部会聚作用，也由六盘山断裂带的变形与运动来承受与转换.横剖面上，六盘山断裂带表现为向东推覆的大型逆冲构造带，主滑脱带位于~25 km深处，之下很可能存在分隔青藏与华北地块的超壳-岩石圈型深断裂带.沿六盘山断裂带中-南段以及更靠南东的陇县-宝鸡断裂带存在总长为120~140 km、至少最近~1400年未发生M ≥ 6?强震破裂的地震空区.地震空区内的断裂，GPS形变显示已有显著应变积累，地震活动上出现为小震稀疏或空缺的部位，以及低b值区，反映那里的断面业已闭锁，并已有高应力积累.因此，六盘山断裂带中-南段和陇县-宝鸡断裂带应是未来可能发生强震/大地震的两个危险地段，潜在地震的最大矩震级估值分别为M_W=7.3±和7.2±.
关键词: 地震构造/
地震空区/
GPS形变/
断层闭锁/
强震危险背景

Abstract:This work was based on integrated multidisciplinary data, including active tectonics, focal mechanism solutions, relocated small earthquakes, historical and modern seismicity, as well as GPS velocity fields. The authors have studied the Liupanshan fault zone (LPSFZ) in China, analyzing its tectonic-dynamic conditions and deformation style, cross-section structure, historical ruptures, GPS deformation, as well as modern micro-seismicity. Furthermore the authors discussed major earthquake hazard associated with the LPSFZ and one of its adjacent fault zones. The study suggests that the NNW-trending LPSFZ has been moving and deforming under the horizontal compression due to the resistance of the stable western part of the North China block, the Ordos block, to the eastward extrusive motion of the northeastern Tibetan block. Besides, lying at the right stepover or restraining bend between the NW-trending and left-lateral strike-slip Haiyuan and Longxian-Baoji fault zones, the LPSFZ absorbs and transforms the locally horizontal convergence of the two strike-slip fault zones. On the cross sections, the LPSFZ shows its characteristic as a large-scale reverse fault thrusting to the east, with a deep detachment zone at depth of~25 km. A seismic gap with a total length of 120~140 km exists along the middle-southern segment of the LPSFZ and the farther southeastern Longxian-Baoji fault zone (LXBJFZ), in which no M ≥ 6? events have occurred during the last~1400 years at least. GPS deformation suggests that the two fault zones along the seismic gap have accumulated significant amount of elastic strain. Furthermore, that modern small earthquakes along several parts of the two fault zones are either sparsely distributed or absent also suggests that some fault patches are locked. In addition, an area with long-term low b-values is present along the middle-southern segment of the LPSFZ and the northernmost segment of the LXBJFZ, probably indicating high stress built up there. Therefore, the middle-southern segment of the LPSFZ and the LXBJFZ should be two fault sections that have high potential of major earthquakes in the future. The estimated maximum moment magnitudes for the potential events are M_W7.3±and M_W7.2±, respectively.
Key words:Seismo-tectonics/
Seismic gap/
GPS deformation/
Fault locking/
Risk of major earthquakes



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