陕西乾陵台洞体应变周年变化的动力诊断  

A Diagnostic Study of Annual Strain Variations in Vault-housed Extensometers at the Geodynamic Observatory Qianling, Shaanxi Province

作　　者：杨小林 危自根[1] 杨锦玲 YANG Xiao-lin;WEI Zi-gen;YANG Jin-ling(Institute of Geodesy and Geophysics,Chinese Academy of Sciences,Wuhan 430077,China;Shaanxi Earthquake Agency,Xi’an 710068,China;Fujian Earthquake Agency,Fuzhou 350003,China)

机构地区：[1]中国科学院测量与地球物理研究所,湖北武汉430077 [2]陕西省地震局,陕西西安710068 [3]福建省地震局,福建福州350003

出　　处：《地震》2020年第2期177-187,共11页Earthquake

基　　金：中国地震局2017年和2020年度震情跟踪课题(2017010206,2020010217,2020010218);地震科技星火计划(XH18023Y)资助。

摘　　要：乾陵台洞体应变自1981年观测以来,其周年变化显著而规律,但物理机制至今尚不清晰。鉴于地表温度年变是引起地壳应变周年变化的一个重要影响因素,本文采用含地形的热固耦合解析模型,定量诊断了地表温度周年变化对洞体应变观测的影响。结果表明,地表温度周年变化5.4 K,便可造成2.2×10^-7的洞体热应变,且理论热应变的变化形态和幅值大致能与观测数据吻合。据此推定,该台洞体应变周年变化主要是地表温度年变化所产生的热应变信号。本文结果对该台热应变的合理改正和观测策略的科学优化,具有重要的参考价值。Strain data in both the NS and the EW component obtained by vault-housed extensometers at the Geodynamic Observatory Qianling, are dominated by annual fluctuations since 1981, the casual mechanism is unclear till now. We show that a significant part of the annual data may result from thermoelastic strain induced by atmospheric temperature variations. We test this hypothesis by computing thermoelastic strain in an inclined homogeneous elastic half-space from atmospheric temperature and comparing the results to the extensometric strain records. The theoretical results suggest that fluctuations in temperature of 5.4 K approximately produce thermoelastic strain amplitudes of up to 2.2×10^-7. Furthermore, the model provides reasonable fits to the amplitudes and patterns of the annual signals recorded by extensometers. Thus, thermal effects on the extensometric strain are a very important factor to explain the annual fluctuations observed by extensometers. Our analysis could potentially contribute to improve the correction models of annual thermoelastic deformation, as well as refine the observation strategy aiming to reduce the signals of annual thermoelastic strain for the Qianling observatory. Especially, these methods will enhance the value of the data for geodynamic studies in the southwestern Ordos margin.

关 键 词：乾陵台 洞体应变 热应变 周年变化 动力诊断 

分 类 号：P315.7[天文地球—地震学]