大渡河水位变化对四川姑咱台钻孔应变观测影响的数值分析  

Numerical analysis of influence of water level fluctuation of Dadu River on Guzan borehole strain meter

作　　者：任天翔[1,2] 杨少华 董培育[1,4] 程惠红[1,2] 石耀霖 REN Tianxiang;YANG Shaohua;DONG Peiyu;CHENG Huihong;SHI Yaolin(Key Laboratory of Computational Geodynamics of Chinese Academy of Sciences,Beijing 100049,China;University of＇Chinese Academy of Sciences,Beifing 100049,China;Institute of Geology,Chinese Academy of Geological Sciences,Beijing 100037,China;Earthquake Administration of Hubei Province,Wuhan 430071,China)

机构地区：[1]中国科学院计算地球动力学重点实验室,北京100049 [2]中国科学院大学,北京100049 [3]中国地质科学院地质研究所,北京100037 [4]湖北省地震局,武汉430071

出　　处：《中国科学院大学学报（中英文）》2018年第5期674-680,共7页Journal of University of Chinese Academy of Sciences

基　　金：国家自然科学基金重大项目(41590865)资助

摘　　要：四分量钻孔应变仪通过孔内4个方向的长期应变监测,有效记录地震、固体潮、长年变化等不同频率的地应力变化。然而,记录中也包含非构造应力因素的干扰,因此了解这些干扰形成的机理是一个重要的问题。四川省姑咱台位于陡峭的大渡河谷底部,不但记录到明显的年周期变化,应变量级达10^(-6),并且每年丰水期,钻孔应变观测到随水位的明显变化。通过弹性力学数值方法讨论河水水位变化对台站产生的应力。初步计算结果表明,姑咱大渡河水数米的涨落对姑咱台探头处产生kPa量级的应力。探头能够记录到水位变化的影响,一方面,说明钻孔应变计的确能够在野外条件下记录到微小应力变化,证明仪器具有很高的灵敏度;另一方面,表明在条件许可的情况下,钻孔应变仪台站选址应该避开陡峭河谷区域,才能减小非构造应力的干扰,突出记录构造应力变化,使观测能更好地应用于地震活动性的研究。Four-component borehole strain gauges detect deformation in four orientations in the borehole to monitor long-term variation of earth stresses,with large frequency coverage including signals from earthquakes,solid earth tides,and secular changes. However,the records also contain disturbances from factors other than tectonic stresses. Therefore,it is an important task to investigate the causes of these disturbances. Guzan station,which is in Sichuan Province,is located on the bottom of a steep valley of Dadu River.This station has recorded not only obvious annual changes of amplitude up to 10^（-6）,but also irregular fluctuations following the rise of river water level in the wet season every year.In this study,stresses generated by the change of river water level are calculated using numerical method of elastic mechanics.Preliminary calculation results indicate that water level fluctuation of several meters in Dadu River produces stress variation of k Pa magnitude.The fact that borehole strain meter can be used to record changes in river water level is significant.On the one hand,the fact shows that the borehole strain gauges indeed detect the very small change in stress variation,which indicates the high sensitivity of the instrument.On the other hand,the fact shows that the location of the strain meter station should be away from steep valleys as far as possible,in order to reduce the interference and highlight the true tectonic stress changes.Observations of improved quality can be applied in the study on relations between earth stress and seismicity.

关 键 词：钻孔应变仪 应变观测干扰 有限元 数值模拟 

分 类 号：P315.7[天文地球—地震学]