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ISSN 2096-7780 CN 10-1665/P

滇西北玉龙雪山东麓断裂晚第四纪活动性研究进展及其构造意义

Research progress on Late Quaternary activity of the eastern foothill fault of Yulong Snow Mountain in Northwestern Yunnan and its tectonic implications

  • 摘要: 川滇块体西边界发育了滇西北裂陷带。裂陷带北缘的玉龙雪山东麓断裂呈南北走向,展布于玉龙雪山和丽江盆地之间,是川滇块体西边界最靠内部的一条断裂。玉龙雪山东麓断裂的形成机制与活动性质不仅关系到川滇西侧复杂构造边界问题,而且能够解释玉龙雪山与哈巴雪山的隆起过程。在1996年丽江MS7.0地震发生后,玉龙雪山东麓断裂引起了关注,但前人的研究结果对该断裂的晚第四纪活动性质存在正断、走滑、逆冲等多种不同认识。表明该断裂长度虽然仅有60 km,却处于一个复杂的构造体系中,理解该断裂的活动特征与孕震行为,对建立川滇块体西部的复杂构造模型意义重大。本文在梳理前人研究资料的基础上,通过卫星影像对断层迹线进行了重新解译,对典型断错地貌进行了分析,发现了比较明显的正断层兼左旋走滑的证据,并在野外初步调查中验证了这些地貌解译证据。基于本文的总结与分析工作,进一步总结了不同性质的玉龙雪山东麓断裂所对应的不同区域构造模型。同时,我们认为从高原扩展角度来看,川滇块体西部的复杂断裂组合具有新生性,可能正在形成新的川滇块体西边界。

     

    Abstract: The northwest Yunnan rift zone develops along the western boundary of the Sichuan-Yunnan block. The N-S trending eastern foothill fault of Yulong Snow Mountain on the northern edge of the rift zone extends between the Yulong Snow Mountain and the Lijiang Basin. It is the innermost part of the western boundary of the Sichuan-Yunnan block. The formation mechanism and activity characteristics of the eastern foothill fault of Yulong Snow Mountain are not only related to the complex structural boundary issues on the western side of Sichuan and Yunnan, but also can explain the uplift process of the Yulong Mountain and the Haba Mountain. After the MS7.0 earthquake in Lijiang in 1996, the eastern foothill fault of Yulong Snow Mountain widely attracted attention. However, previous research results about the Late Quaternary activity of this fault were diverse, including normal faulting, strike-slip faulting, and thrusting. It indicates that although this fault is only 60 kilometers long, it belongs to a complex tectonic system. Understanding the activity characteristics and earthquake-generating behavior of this fault is of great significance for establishing a complex structural model in the western Sichuan-Yunnan block. This article summarizes previous research data, reinterprets the fault based on satellite images, analyzes the typical fault-related landforms and identifies clear evidence of a combination of normal faulting and sinistral strike-slip along the fault. Field investigations have further validated these interpretations. Based on the conclusions and analysis presented in this paper, we have summarized different regional tectonic models corresponding to the different activity properties of eastern foothill fault of Yulong Snow Mountain. Meanwhile, from the perspective of plateau expansion, it is believed that the complex fault combination in the western Sichuan-Yunnan block is new and is forming a new western boundary of the Sichuan-Yunnan block.

     

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