东昆仑断裂带活动速率研究概观

An Overview of Activity Rate along the East Kunlun Fault Zone

东昆仑断裂带是青藏高原内部的主要巨型左旋走滑断裂。了解该断裂带的活动速率对于理解青藏高原的隆升演化和大陆构造变形过程至关重要。近年来,多学科的研究成果揭示了东昆仑断裂带活动速率时空变化特征的阶段性认识。本文综述了东昆仑断裂带的几何分段、深部结构和在数十年至数十万年时间尺度下的活动速率研究进展,并探讨了未来的研究方向。东昆仑断裂带呈现典型的走滑断裂几何结构,自西向东形态逐渐变得复杂,呈现出“马尾状”的构造形态。通过遥感、地质调查、古地震和大地测量等方法,研究者测量了东昆仑断裂带的水平和垂直活动速率。研究结果显示,水平活动速率自西向东总体减小。以阿尼玛卿山(99°E~100°E)为界,西部地区的水平活动速率基本稳定在10~12 mm/a,变化不大;东部地区的水平活动速率范围为1~12 mm/a,不大于西部,但该速率值存在较大争议。垂直运动速率则呈现出相反的趋势,西部约为水平活动速率的10%,而东部逐步增加。这表明西部的水平变形仍有部分在东部转换为垂向隆升。在地貌位错量和大地测量数据相似的情况下,活动速率的差异可能与位错量相应的起始年龄差异、震后黏弹性松弛效应、次级断裂和巴颜喀拉块体内部断裂、岷山隆起等因素有关。目前,东昆仑断裂带的水平运动已有深入研究,未来可以尝试补充其垂直运动的研究,利用水平和垂直速率之比的变化来探讨水平走滑和垂向隆升变形的转变过程。不同学科对于东昆仑断裂带的活动速率有不同的认识,这是由于该断裂带具有复杂的几何结构,并且不同学科的研究方法在时空尺度上也存在差异。因此,在综合分析多学科数据时,需要考虑这些差异对结果解释的影响,并尽可能采用相同或相近时间尺度下的数据进行对比。

Since the neotectonic period,the Qinghai-Tibet Plateau has undergone intense uplift and eastward sliding.The East Kunlun Fault Zone(EKF)is one of the major sinis-tral strike-slip faults in the Qinghai-Tibet Plateau.Its rate of activity has become one of the key data to understand this process.In recent years,the EKF activity rate has been obtained through methods such as remote sensing,geological surveys,paleoearthquakes,and geodesy.The time scale of different research methods ranges from decades to tens of thousands of years.Therefore,the differences in results and their reasons can be analyzed from different disciplines.Furthermore,it is formed through a phased understanding of the variation in the EKF activity rate.The results show that the EKF exhibits typical strike-slip fault geometry.Its structure changes from simple to complex"horse-tail"shaped forms as one moves from west to east.The eastern endpoint is limited by the struc-tural trend change zone between the EKF,Minjiang Fault,and Longmenshan Fault.The horizontal slip rate decreases overall from west to east.Taking the Animaqing Mountains(99°E~100°E)as the boundary,the horizontal activity rate in the western region is basi-cally stable at 10~12 mm/a,with little change,and the horizontal activity rate in the eastern region is 1~12 mm/a,which is not greater than that in the west,but is more con-troversial.In the case of similar geomorphological dislocations and geodetic data,the difference in activity rates may be related to the difference in the initial age of dislocations and the post-earthquake viscoelastic relaxation effect.Most of the reduced activity rate may be due to secondary faults of the East Kunlun fault and internal faults of the Bayan Har block,or to the Minshan uplift on the east side.Sporadic results show that the verti-cal motion rate on the west side is about lo%of the horizontal activity rate,while the ver-tical motion rate on the east side gradually increases.This indicates that part of the hori-zontal deformation on the west side is still converted to vertical uplift on the east side.At present,when the horizontal motion of the East Kunlun fault zone has been studied in depth,future research can try to supplement the study of vertical motion and use the change of the ratio of horizontal and vertical velocities to explore the transformation process of horizontal strike-slip and vertical uplift deformation.Different disciplines have different understandings of the EKF activity rate,which is due to the complex geometric structure of the fault zone and differences in research methods across disciplines on the spatiotemporal scale.