青藏高原大型地震断裂带的变形机制  

Deformation Mechanism of Large Earthquake Fault Zone in the Tibetan Plateau

作　　者：张蕾 李海兵[1,2] 王焕 吴琼[3] 杨少华 孙知明 司家亮[1,2] Marie-Luce CHEVALIER 曹勇[4] 郑勇[1,2] 潘家伟 刘栋梁 赵中宝[1,2] 马绪宣 卢海建[1,2] ZHANG Lei;LI Haibing;WANG Huan;WU Qiong;YANG Shaohua;SUN Zhiming;SI Jialiang;Marie-Luce CHEVALIER;CAO Yong;ZHENG Yong;PAN Jiawei;LIU Dongliang;ZHAO Zhongbao;MA Xuxuan;LU Haijian(MNR Key Laboratory of Continental Dynamics,Institute of Geology,Chinese Academy of Geological Sciences,Beijing 100037;Jiangsu Donghai Continental Deep Borehole Crustal Activity National Observation and Research Station,Lianyungang,Jiangsu 222300;Beijing Petroleum Machinery Co.,Ltd,Beijing 102206;MNR Key Laboratory of Paleomagnetism and Tectonic Reconstruction,Institute of Geomechanics,Chinese Academy of Geological Sciences,Beijing 100081)

机构地区：[1]中国地质科学院地质研究所,自然资源部大陆动力学重点实验室,北京100037 [2]江苏东海大陆深孔地壳活动国家野外科学观测研究站,江苏连云港222300 [3]北京石油机械有限公司,北京102206 [4]中国地质科学院地质力学研究所,自然资源部古地磁与古构造重建重点实验室,北京100081

出　　处：《地球学报》2024年第6期854-870,共17页Acta Geoscientica Sinica

基　　金：国家自然科学基金项目(编号:42230312,42172262,42372266,42072240,42020104007,42272270,42374121);中国地质科学院基本科研业务费项目(编号:J2403);中国地质调查局地质调查项目(编号:DD20221630)。

摘　　要：近年来,大震频发,地震发生机制和地震断裂作用的研究已成为当今社会的重大课题,而断裂带的变形机制,尤其是大型地震断裂带的变形机制是认识断裂活动性和地震发生机制的关键。本文通过介绍青藏高原东缘龙门山断裂带和鲜水河断裂带的最新研究成果,探讨青藏高原大型地震断裂带的变形机制,主要认识如下:(1)汶川地震使不同性质断层同时破裂,并在地壳浅部(~732.6 m深度)富流体断层泥中发生了熔融作用,颠覆了地震的传统认识,深化了对浅部断层力学性质的认识。(2)龙门山断裂带映秀—北川断裂带在晚三叠世曾经发生Mw7.4~7.9级的逆冲-左行走滑大地震,断裂岩的高磁化率各向异性度值指示了大地震活动。(3)汶川—茂县断裂带在新生代时期存在三期不同构造变形,青藏高原东缘不存在下地壳隧道流模式。(4)龙门山断裂带汶川—茂县断裂带曾经发生了摩擦热温度>500℃的大地震活动,孕震环境为还原性的含有硫化物的低温热液流体环境。(5)强震频发的鲜水河断裂带是藏东南物质外迁的主要边界,具有长期蠕滑变形行为,流体作用较强,流体的注入明显提高断层核部强矿物含量,促进了蠕滑断层的局部变强。上述认识丰富和完善了断裂作用理论,提高了对青藏高原大型地震断裂带变形机制的认识,为断裂带活动性、地震发生机制、地震危险性评估和防震减灾提供了科学依据。Recently,large earthquakes have occurred frequently,and earthquake mechanism and earthquake faulting have become important topics in society.The deformation mechanism of fault zones,especially large earthquake fault zones,is the key to understanding fault activity and earthquake mechanisms.The aim of this study was to discuss the deformation mechanism of the large earthquake fault zone in the Tibetan Plateau by analyzing recent research on the Longmen Shan and Xianshuihe fault zones in the eastern Tibetan Plateau.The results are as follows:(1)The Wenchuan earthquake simultaneously ruptured on different faults and formed a pseudotachylyte vein at an extremely shallow depth(~732.6 m),which was generated in an unconsolidated,fluid-rich fault gouge.This finding overturns our traditional understanding of earthquakes and deepens our understanding of the mechanical properties of shallow faults.(2)A Late Triassic Mw~7.4 to 7.9 earthquake had occurred along the Yingxiu–Beichuan fault,Longmen Shan fault zone,and the focal mechanism of this large magnitude earthquake was left-lateral,strike-slip motion.The high degree of magnetic anisotropy in the fault rocks is an indication of a high-strain seismogenic environment and a new important indicator of large earthquakes.(3)Three deformation phases were identified in the Wenhuan–Maoxian fault zone during the Cenozoic,in contrast to the predictions of the lower crustal channel-flow extrusion models.(4)Large earthquakes with high frictional heating(>500°C)have occurred along the Wenhuan–Maoxian fault zone in the past,and the seismogenic environment was a reductive environment with low-temperature hydrothermal fluids.(5)The Xianshuihe fault system is the main boundary for the outward migration of material in southeastern Tibet.The Xianshuihe fault zone,with frequent large earthquakes,exhibits long-term creep deformation behavior.The fluid influx increases the content of strong minerals within the fault core,thereby locally strengthening the creeping fault.These results enric

关 键 词：断裂岩 变形机制 龙门山断裂带 鲜水河断裂带 青藏高原 

分 类 号：P315.2[天文地球—地震学]