“V”型共轭走滑断裂：特征、形成机制及其对青藏高原东南缘晚新生代变形的启示

V-Shaped Conjugate Strike-Slip Faults: Characteristics, Formation Mechanisms and Implications for the Late Cenozoic Deformation in the Southeastern Tibetan Plateau

摘要

“V”型共轭走滑断裂是指共轭角为钝角的共轭走滑断裂，其“V”型开口方向为锐角且指示最大拉伸方向.前人开展了大量关于“V”型共轭走滑断裂发育背景及动力学机制的研究，但是目前未有针对“V”型共轭断裂几何学、运动学有关的综述.归纳已有“V”型共轭走滑断裂的几何学、运动学特征，总结现存的“V”型共轭走滑断裂的动力学机制，并选取青藏高原东南缘“V”型共轭走滑断裂，进行实例分析.分布于美国西部、欧亚板块中西部和西藏中部的“V”型共轭走滑断裂特征揭示共轭角大小与断裂滑动速率及断裂长度均呈负相关关系.“V”型共轭走滑断裂的成因主要有：（1）断裂剪切面的后期旋转，（2）断裂形成于先存构造薄弱带，（3）断裂遵循对偶一般剪切模型，（4）断裂遵守最大有效力矩法则.基于地球物理数据、地形高差对比以及几何特征的分析，认为青藏高原东南缘川滇块体内部的巴塘-理塘共轭走滑断裂和得荣-乡城共轭走滑断裂的成因机制符合对偶一般剪切模型中的重力扩展，这为理解青藏高原东南缘下地壳连续变形的动力学机制提供了重要启示.

Abstract

The V-shaped conjugate strike-slip fault system is defined as strike-slip faults with obtuse conjugate angles, whose opening side has an acute angle between the V-shaped faults, pointing to the direction of maximum extension. Previous studies on V-shaped conjugate strike-slip faults mostly focused on their development background and associated dynamic mechanisms. However, few literatures exist to comprehensively review the geometry and kinematics of V-shaped conjugate strike-slip faults. Here, we firstly summarize previous findings on the geometry, kinematic characteristics and formation mechanisms of existing V-shaped conjugate strike-slip faults, and then select the V-shaped conjugate strike-slip faults in the southeastern Tibetan Plateau for a case analysis. The characteristics of V-shaped conjugate strike-slip faults in the western United States, central and western Eurasian plate and central Tibet show a negative relation among conjugate angles and corresponding fault slip rates and fault lengths. The four formation mechanisms of the V-shaped conjugate strike-slip faults are 1) the fault planes experienced rotation after their formation, 2) the faults were reactivated along preexisting structurally weak zones, 3) the faults followed the paired general shear model and 4) the fault evolved according to the maximum-effective-moment criterion. Integrating analyses of geophysical data, elevation difference and geometric characteristics, we infer that the development of V-shaped conjugate strike-slip faults (Batang-Litang and Derong-Xiangcheng faults) in the Chuan-Dian block in the southeastern Tibetan Plateau, is consistent with gravitational spreading of the Tibetan lithosphere under the paired general shear model. This provides important insights for understanding the continuum crustal deformation in the southeastern Tibetan Plateau.

关键词

“V”型共轭走滑断裂 / 几何学 / 运动学 / 成因机制 / 青藏高原东南缘 / 构造地质学

Key words

V-shaped conjugate strike-slip faults / geometry / kinematics / formation mechanism / southeastern Tibetan Plateau / structural geology

基金资助

国家自然科学基金项目(41941016;51988101;41972227)

浙江省钱江人才计划项目(QJD190202)

浙大百人计划项目