抽水对泰安地震台钻孔分量应变的影响及其机制  

INFLUENCE OF PUMPING ON FOUR-COMPONENT BOREHOLE STRAIN AT TAI’AN SEISMIC STATION AND ITS INTERFERENCE MECHANISM

作　　者：贾媛[1] 甘卫军[2] 李杰[1] 朱成林[1,2] 殷海涛[1] 卢双苓[1] 鞠佳斌 JIA Yuan;GAN Wei-jun;LI Jie;ZHU Cheng-lin;YIN Hai-tao;LU Shuang-ling;JU Jia-bin(Shandong Earthquake Agency,Jinan 250014,China;State Key Laboratory of Earthquake Dynamics,Institute of Geology,China Earthquake Administration,Beijing 100029,China;Tonghua Seismic Station of Jilin Province,Tonghua 134000,China)

机构地区：[1]山东省地震局,济南250014 [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]吉林省通化地震台,通化134000

出　　处：《地震地质》2019年第6期1429-1443,共15页Seismology and Geology

基　　金：山东省自然科学基金(ZR2017LD009);山东省重点研发计划项目(2018GSF120007);山东省地震局科研基金(JJ1606Y)共同资助

摘　　要：抽水干扰在钻孔应变观测中常见且影响显著,为了捕捉到真实的地震前兆信息,必须对其干扰机制进行研究。统计结果表明,近年来泰安台RZB-3钻孔分量应变受抽水干扰严重。对此,文中以一个现场查明抽水信息的抽水干扰为例,分正常抽水、中断抽水和恢复抽水3个时段计算了钻孔的主应变状态,并利用集中载荷模型反演了应变仪相对抽水源集中力的深度和集中力,在此基础上正演模拟计算了抽水干扰对周边区域的影响。结果表明:1)反演的抽水源集中力位于抽水井底部及其下方附近,与实际情况吻合,模型较好地模拟了抽水干扰对钻孔应变的影响机制和程度;2)钻孔分量应变观测的应变状态与抽水干扰模型正演结果较为一致,根据观测结果计算的钻孔主应变反映了不同抽水状态下钻孔的应变状态;3)反演的抽水源集中力与所抽出的水量载荷相比,抽水过程对岩石孔隙压力的影响要显著得多。Four-component borehole strainmeter( FCBS) is one kind of high-precision borehole strain observation instruments invented in China. As a kind of near-surface deformation observation instrument,FCBS is also easily disturbed by the external environment factors. As a common factor,pumping has significant influence on FCBS observation. Existing studies mostly identify the pumping interference from the perspective of observation curve morphology,relatively few studies focus on its interference mechanism. In order to truly capture earthquake precursor information,it is necessary to study the interference mechanism. In recent years,RZB-3 type FCBS at Tai’ an seismic station has been seriously affected by pumping,so it is necessary and also feasible to study the interference mechanism of pumping. Since the influence of pumping interference on borehole strainmeter is common,this work would be very practical and be used for reference by other borehole strain observation stations.We find that the original observation curves and observed surface strain,shear strain from RZB-3 type FCBS at Tai’ an seismic station have the characteristics of synchronous change with the borehole water level,in which the linear correlation coefficient between the two observed shear strain curves and borehole water level reached 0. 70 and 0. 82 respectively. We further find that the principal strain direction of borehole and borehole water level after normalization meet the nonlinear function as y = 1.217 arctan( x)0.224-0.284. The above phenomenon indicates that the observation of RZB-3 type FCBS at Tai’an seismic station is significantly affected by the borehole water level,and the influence is more obvious and the gradient is larger at the stage of low water level. Pumping interference often appears in low water level stage and changes the rock pore pressure state. Statistics show that pumping interference affects the borehole strain state.To investigate the interference mechanism of pumping to RZB-3 type FCBS at Tai’ an seismic statio

关 键 词：钻孔分量应变 抽水干扰 应变状态 集中载荷模型 干扰机制 孔隙压力 

分 类 号：P315.72^+7[天文地球—地震学]