淮南深地重力观测的环境噪声评估与慢地震探测潜力  

Environmental noise assessment of underground gravity observation in Huainan and the potential capability of detecting slow earthquake

作　　者：王振宇 王赟[2] 徐如刚[3] 刘泰 付广裕 孙和平 WANG ZhenYu;WANG Yun;XU RuGang;LIU Tai;FU GuangYu;SUN HePing(Institute of Earthquake Forecasting,China Earthquake Administration,Beijing 100036,China;School of Geophysics and Information Technology,China University of Geosciences,Beijing 100083,China;Anhui Earthquake Administration,Hefei 230031,China;State Key Laboratory of Geodesy and Earth′s Dynamics,Innovation Academy for Precision Measurement Science and Technology,Chinese Academy of Sciences,Wuhan 430077,China)

机构地区：[1]中国地震局地震预测研究所,北京100036 [2]中国地质大学(北京)地球物理与信息技术学院,北京100083 [3]安徽省地震局,合肥230031 [4]中国科学院精密测量科学与科技创新研究院大地测量与地球动力学国家重点实验室,武汉430077

出　　处：《地球物理学报》2022年第12期4555-4568,共14页Chinese Journal of Geophysics

基　　金：国家自然科学基金项目(41874003);中国地震局地震预测研究所基本科研业务费专项(CEAIEF20220212);国家自然科学基金项目(U1839208,62127815,42150201)联合资助.

摘　　要：深地实验室的低噪声特性为高精度连续重力观测提供了理想的外部条件.为了揭示深地观测环境对重力观测精度的提升效果,本研究利用CG-5型和CG-6型各两台重力仪,在淮南煤矿的地下和地表同时开展重力观测.为减小仪器性能差异对结果的影响,先在淮北重力站进行同址观测.研究结果表明,相比于地表观测,地下观测可以减少1/3至1/2的线性漂移和1/3左右的非线性漂移,提取的潮汐因子精度也更高.地下非线性漂移的功率谱密度比地表低,二者差异在半日波频段最大可达15 dB.相比于地表和山洞,深地观测在次地震频段有明显的低噪声优势.地震位错理论计算结果表明,冲绳海沟7级左右的地震可在淮南深地试验场产生大约0.003μGal的重力变化,超过0.001μGal的超导重力静态观测精度.因此有望利用淮南深地实验室,在次地震频段的低噪声优势环境下开展超导连续重力观测,捕捉冲绳海沟可能存在的7级以上慢地震事件.Deep underground laboratory with ultra-low noise is ideal for high-precision continuous gravity observation.To reveal the effect of deep environment on the enhancement of the precision,the current study conducted gravimetric surveys above ground and underground at the Huainan underground laboratory(whose predecessor is the Huainan coal mine),simultaneously,with the utilization of 2 sets of CG-5 and CG-6 gravimeters.In order to reduce the influence of different performances between various instruments,a co-site observation was conducted at the Huaibei gravity station previously.The results show that the underground observation can reduce 1/3 to 1/2 of the linear drift and about 1/3 of the nonlinear drift compared with the surface observation.The precision of tidal factor extracted from underground observation is higher than that from surface observation as well.The power spectra density of underground non-linear drift is lower than that of surface,with the maximum difference of 15 dB.The noise level of underground observation in sub-seismic band is much lower than those of surface and cave.The results of earthquake dislocation theory show that an M_(W)7.0 earthquake at Okinawa Trench may lead to gravity change of 0.003μGal,which exceeds the static precision of superconducting gravimeter(0.001μGal),at Huainan Deep Laboratory.In summary,the low noise in sub-seismic band of Huainan Deep Laboratory shall be combined with continuing superconducting gravimeter observation and used for detecting slow earthquakes larger than M_(W)7.0 at Okinawa Trench.

关 键 词：地下实验室 重力观测 潮汐分析 功率谱密度 慢地震 

分 类 号：P312[天文地球—固体地球物理学] P315[天文地球—地球物理学]