由km尺度的跨断层基线测量断层近场运动与变形——川滇块体东边界2个场地的初步实验  

NEAR-FAULT DISPLACEMENT AND DEFORMATION OBTAINED FROM ONE-KILOMETER-LONG FAULT-CROSSING BASELINE MEASUREMENTS—A PRELIMINARY EXPERIMENT AT 2 SITES ON THE EASTERN BOUNDARY OF THE SICHUAN-YUNNAN BLOCK

作　　者：曹建玲[1] 张晶[1] 闻学泽[2] 冯蔚[1] 石耀霖 CAO Jian-ling;ZHANG Jing;WEN Xue-ze;FENG Wei;SHI Yao-lin(Key Laboratory of Earthquake Prediction,Institute of Earthquake Forecasting,China Earthquake Administration,Beijing 100036,China;State Key Laboratory of Earthquake Dynamics,Institute of Geology,China Earthquake Administration,Beijing 100029,China;University of Chinese Academy of Sciences,Beijing 100049,China)

机构地区：[1]中国地震局地震预测研究所,中国地震局地震预测重点实验室,北京100036 [2]中国地震局地质研究所,地震动力学国家重点实验室,北京100029 [3]中国科学院大学,北京100049

出　　处：《地震地质》2020年第3期612-627,共16页Seismology and Geology

基　　金：国家重点研发计划项目(2017YFC1500502-02);国家自然科学基金(41974111,41774111);中国地震局地震预测研究所基本科研业务专项(2014IES010201)共同资助。

摘　　要：现行的基于数十至百m长的跨断层短基线的测量方法精度较高,但往往不能有效跨越大型活动断裂带进行观测;而GNSS目前受站点密度及观测精度所限,对断层近场尤其是运动速率偏低的断层开展形变观测的分辨率较差。基于上述现状,在川滇块体东边界构造带新布设2个实验场地,分别跨越则木河断裂大箐梁子段和昭通断裂的龙树分支进行测量。实验利用km尺度跨距的基线测量活动断裂带的近场运动与变形,获得3a的实验观测数据。文中首先介绍了场地选建、监测断裂、基线测量方法以及实验观测结果,然后利用测量资料,基于刚体、弹性和组合模型3种假设条件计算分析这2个场地的断层近场位移和应变。则木河断裂大箐梁子段在刚体模型下2盘近场平行断裂走向的位移分量在±3mm内波动,无明显趋势变化;垂直断裂走向的位移分量在2015—2016年持续下降,反映断裂呈横向水平压缩,累计降幅达6mm,但2017年出现近2mm的横向水平拉张;弹性模型下该断裂段的横向水平应变分量εy以挤压为主,年变化幅度接近1×10^-5,另外2个应变分量均为10^-6量级。昭通断裂龙树分支2盘近场的相对位移虽然变化较小,但表现出与该断裂地质活动一致的右旋走滑特征,位移速率约0.7mm/a;沿该分支断层走向的应变分量εx为挤压状态,量值不超过2×10^-6;垂直断层走向的应变分量εy则以拉张为主。文中还讨论了应用组合模型的效果与问题。The current and conventional fault-crossing short baseline measurement has a relatively high precision,but its measurement arrays usually fail to or cannot completely span major active fault zones due to the short length of the baselines,which are only tens to 100 meters.GNSS measurement has relatively low resolution on near-fault deformation and hence is not suitable for monitoring those faults with low motion and deformation rates,due to sparse stations and relatively low accuracy of the GNSS observation.We recently built up two experimental sites on the eastern boundary of the active SichuanYunnan block,one crossing the Daqing section of the Zemuhe Fault and the other crossing the Longshu section of the Zhaotong Fault,aiming to test the measurement of near-fault motion and deformation by using fault-crossing arrays of one-kilometer-long baselines.In this paper,from a threeyear-long data set we firstly introduce the selection of the sites and the methods of the measurement.We then calculate and analyze the near-field displacement and strain of the two sites by using three hypothetical models,the rigid body,elastic and composed models,proposed by previous researchers.In the rigid body model,we assume that an observed fault is located between two rigid blocks and the observed variances in baseline lengths result from the relative motion of the blocks.In the elastic model,we assume that a fault deforms uniformly within the fault zone over which a baseline array spans,and in the array baselines in different directions may play roles as strainmeters whose observations allow us to calculate three components of near-fault horizontal strain.In the composed model,we assume that both displacement and strain are accumulated within the fault zone that a baseline array spans,and both contribute to the observed variances in baseline lengths.Our results show that,from the rigid body model,variations in horizontal fault-parallel displacement component of the Zemuhe Fault at the Daqing site fluctuate within 3 mm without obvious

关 键 词：km跨距基线测量 跨断层测量 实验观测 断层近场位移 断层近场应变 

分 类 号：P315.2[天文地球—地震学]