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  何建军,任俊杰,丁锐,徐锡伟,赵俊香,胡幸平.青藏高原东缘龙日坝断裂带南段晚第四纪活动及其构造意义[J].震灾防御技术,2016,11(4):707-721, DOI:10.11899/zzfy20160402.

青藏高原东缘龙日坝断裂带南段晚第四纪活动及其构造意义
摘要:    因缺少详细的地质调查,关于龙日坝断裂带南段是否具有强烈的晚第四纪活动及其在青藏高原东缘应变分配中承担的作用目前尚不清楚。卫星影像解译和野外调查结果表明龙日坝断裂带南段仅东南支存在晚第四纪活动,全长约50km,总体以右旋走滑为主,兼有逆断分量,全新世以来右旋平均走滑速率约为0.6mm/a,平均垂直滑动速率约为0.4mm/a。龙日坝断裂带南段活动强度较中段明显偏弱,但具备发生MW7级左右地震的能力,在距今约800年以来曾发生过地表破裂型事件。结合重定位地震结果来看,龙日坝断裂带西侧和龙门山断裂带地震活跃,之间的丹巴地区可能主要表现为褶皱变形而地震活动微弱。青藏高原东缘之下的滑脱面自川西高原到四川盆地从约15km逐渐变深至20km左右,而又变浅,约为10km,这种滑脱面的深度变化可能是龙门山隆升和孕震的驱动机制。这项研究有助于川西地区的地震危险性评价和深入理解青藏高原东缘的应变分配和隆升机制。
作者单位
何建军 中国地震局地壳应力研究所(地壳动力学重点实验室)北京 100085 
任俊杰 中国地震局地壳应力研究所(地壳动力学重点实验室)北京 100085 
丁锐 中国地震局地壳应力研究所(地壳动力学重点实验室)北京 100085 
徐锡伟 中国地震局地质研究所北京 100029 
赵俊香 中国地震局地壳应力研究所(地壳动力学重点实验室)北京 100085 
胡幸平 中国地震局地壳应力研究所(地壳动力学重点实验室)北京 100085 
关  键  词:龙日坝断裂带  南段  龙门山断裂  青藏高原东缘  丹巴背斜
DOI:10.11899/zzfy20160402
基金项目:地震行业专项(201408023)、国家自然基金项目(41102134、41572193)和中国地震局地壳应力研究所中央级公益性科研院所基本科研业务专项(ZDJ2014-10)共同资助
收稿日期:2016-04-11
作者简介:何建军,男,生于1994年。在读硕士研究生。主要从事活动构造方面的研究。E-mail: 396551702@qq.com
通讯作者:任俊杰,男,生于1979年。博士,副研究员。主要从事活动构造、构造地貌与地震危险性分析等方面的研究。E-mail: renjunjie@gmail.com
Late Quaternary Activity of the Southern Segment of Longriba Fault Zone in Eastern Tibet and Its Tectonic Implications
Abstract:      It remains unclear about Late Quaternary activity of the southern segment of Longriba fault zone and its role of strain partitioning in eastern Tibet. Interpretation of satellite imagery and field observations show that only the southeastern branch of the southern segment of Longriba fault zone with length of about 50 km is active in late Quaternary. This branch is dextral strike slip of about 0.6 mm/a with reverse component of about 0.4 mm/a. Although the southern segment of Longriba fault zone is apparently less active than its middle segment but it has a potential of large earthquake with moment magnitude about 7.0. Since about 800 years before present, a surface-ruptured event has occurred on the southern segment of Longriba fault zone. From relocated earthquakes, the western part of the Longriba fault zone and the Longmenshan are very active. Between them, the Danban area is dominant by folding with low seismicity. The depth of the decollement is from~15 km beneath the inner Plateau, to about 20 km beneath the Longmenshan, and decreases to~10 km beneath the Sichuan basin. The depth variation of the decollement beneath eastern Tibet possibly contributed to the uplift of the Longmenshan and seismogenic zone. Our results are helpful of seismic hazard evaluation of western Sichuan as well as for understanding the pattern of strain partitioning and the mechanism of tectonic uplift in eastern Tibet.
Keywords:  Longriba fault zone  Southern segment  Longmenshan fault zone  Eastern Tibet  Danba anticline
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