InSAR数据约束的鲜水河断裂带北西段震间滑动速率及浅部蠕滑特征  

INTERSEISMIC SLIP RATES AND SHALLOW CREEP ALONG THE NORTHWESTERN SEGMENT OF THE XIANSHUIHE FAULT FROM INSAR DATA

作　　者：陈毅 赵斌[1] 熊维[1] 王伟[1] 余鹏飞[1] 余建胜[1] 王东振[1] 陈威[1] 乔学军[1] CHEN Yi;ZHAO Bin;XIONG Wei;WANG Wei;YU Peng-fei;YU Jian-sheng;WANG Dong-zhen;CHEN Wei;QIAO Xue-jun(Key Laboratory of Earthquake Geodesy,Institute of Seismology,China Earthquake Administration,Wuhan 430071,China)

机构地区：[1]中国地震局地震研究所,地震大地测量重点实验室,武汉430071

出　　处：《地震地质》2023年第5期1074-1091,共18页Seismology and Geology

基　　金：中国地震局地震科技星火计划项目(XH21020)。

摘　　要：作为中国大陆最为活跃的断裂带之一,鲜水河断裂现今的滑动模式,尤其是北西段的浅部蠕滑特征长期以来备受关注。文中首先利用Sentinel-1卫星降轨数据,基于小基线集时序分析(SBAS)方法获取鲜水河断裂带北西段2014—2021年的地表视线向(LOS向)平均速度场;再采用弹性螺旋位错模型拟合InSAR跨断层剖面速度,估计断层的长期滑动速率和浅部蠕滑速率;最后结合黏弹性地震周期模型分析炉霍段地震的复发周期、下地壳和上地幔流变对滑动速率估计的影响。InSAR处理结果显示,断层两侧LOS向速度场呈现出明显的速度差异。使用弹性螺旋位错模型估计得到的鲜水河断裂北西段的断层滑动速率为7.2~11.0mm/a,自西向东逐渐减小。断裂带浅部蠕滑速率为0.3~3.1mm/a,蠕滑主要集中在虾拉沱和道孚—松林口之间。基于历史地震的复发周期及青藏高原东缘下地壳和上地幔黏滞系数的研究,文中采用黏弹性地震周期模型反演得到炉霍段的滑动速率为(7.91±0.3)~(9.85±0.4)mm/a,略低于纯弹性螺旋位错模型的结果((10.14±0.5)mm/a)。Located in the eastern boundary of the Qinghai-Tibetan plateau,the Xianshuihe fault zone is one of the most active left-lateral strike-slip faults in Chinese mainland.As the southern boundary of the Bayanhar block,the Xianshuihe Fault accommodates the southeastward transport of material toward southeastern Asia.Earthquakes have occurred frequently along this fault,especially in the northwestern segment.More than 20 earthquakes with MW>6.0 have ruptured since 1700.The most recent MW>7 earthquake was the Luhuo earthquake in 1973,and the most recent MW>6 earthquake was the MW6.6 Luding earthquake in 2022.As one of the most active faults in China's Mainland,the present slip pattern of the Xianshuihe Fault,especially the shallow creep characteristics along its northwestern segment,has attracted much attention.The primary goal of determining slip rates of active faults using geodetic data is to quantify the seismic potential of the faults.Illuminating the long-term slip rate and shallow creep distribution of faults is the basis for calculating the seismic moment rate and evaluating the seismic potential.Due to the backwardness of early measurement methods,the seismic deformation along the Xianshuihe Fault was previously based on geologic,cross-fault short baseline and leveling surveys.With the application of GPS in tectonic geodesy,more and more GPS stations are installed near active faults,which provide accurate constraints on the long-term slip rates of the fault.Subsequently,the appearance of InSAR technology has brought a beneficial supplement to GPS,providing high spatial resolution surface velocity maps,which have been widely used to measure deep and shallow creep along active faults.It is the key to accurately characterize the fault slip behavior and evaluate the seismic potential.In this study,119 Sentinel-1 satellite descent data from December 2014 to December 2021 were processed to obtain the average line-of-sight(LOS)velocity field of the northwestern segment of the Xianshuihe Fault based on the small baseli

关 键 词：鲜水河断裂带 震间滑动速率 浅部蠕滑 黏弹性地震周期模型 

分 类 号：P315.2[天文地球—地震学]