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《地震地磁观测与研究》2016,(3)
山西静乐观测井具有含水层系统对地壳应力—应变响应灵敏的优势,其水位变化对应地震,可间接反映地壳应力—应变特征。2015年7月以来,静乐井水位快速上升,对观测环境、仪器及人为干扰进行分析,并进行同层地下水开采及抽水试验,分析该井水位异常原因,结果发现,降雨量、抽水试验对静乐井水位变化影响不大,而生产用同层地下水开采量减小是该井水位变化的主要原因。 相似文献
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本文从时域和频域分别对福州台和永安台的体应变和井水位资料观测的一致性进行了分析,并对其力学机制进行了深入探究,在此基础上阐明了二者观测一致性的物理含义.时域内的分析结果显示:福州台体应变与井水位的相关系数为0.7939,钻孔系统的灵敏度为0.0558 mm/10-9,井水位与体应变观测曲线十分相似;永安台体应变与井水位的相关系数为-0.7543,钻孔系统的灵敏度为-0.0005 mm/10-9,井水位与体应变曲线呈镜像对称,这表明两台站的井水位与体应变观测高度相关,且二者的相位滞后近似为零.在频域内,分别对福州台2012年3—5月及永安台2014年3—5月的井水位和体应变资料进行维尼迪柯夫调和分析,分别获取半日波、全日波数个波群的逐月潮汐因子和相位滞后,并计算得到了钻孔系统的灵敏度和井水位相对于体应变的相位滞后.结果表明,3个月中大多数波群的灵敏度十分相近,而且与时域内所得年周期低频分量的灵敏度较接近,但相位滞后误差较大,这可能与采用反正切公式计算相位滞后受计算误差影响有关,即非线性的反正切公式对计算误差具有放大累积效应,因此相位滞后应以时域分析所得接近于零的结果为准.综上,时域和频域的分析结果表明,福州台和永安台的井水位对体应变的响应基本上是线性时不变的,二者观测一致性的根本原因在于两台站的承压含水层井水位观测系统基本上是满足叠加性、齐次性和时不变的物理可实现因果系统. 相似文献
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对中国临夏台2013年至2014年两年的井水位和四分量钻孔应变资料进行了预处理以消除趋势与突跳.根据文献(Means,1982;Young and Budynas,2005),相互正交的两条测线的应变观测值之和等于面应变.文献(刘序俨等,1988)证明近地表的面应变的2/3等于体应变,因此,可由4分量钻孔应变观测值得到钻孔体应变,然后根据体应变与井水位观测资料,从时域和频域对该钻孔系统的性质进行了论证.结果表明,在时域,体应变与井水位高度负相关.钻孔系统的灵敏度为—0.1620mm/10-9.把两年中的某两个月份的两者时间坐标轴和纵轴比例尺放大,发现井水位曲线的峰/谷与体应变观测曲线的谷/峰一一对应,两者的相位滞后非常小.在频域内,本文采用Venedikov调和分析方法分别取得了井水位与体应变9个月的半日波与全日波数个波群的逐月潮汐因子与相位滞后,然后作简单计算,得到了钻孔系统对上述波群的灵敏度与相位滞后.结果表明9个月中大多数波群的灵敏度不但十分相近,且非常接近由时域得到的周年频率分量的灵敏度,但相位滞后误差较大,本文对此进行了分析,认为由反正切得到的相位滞后受计算误差影响较大,应以时域经审视所得的相位滞后接近于零为准.通过时域与频域的分析,表明井水位对体应变的响应基本是线性时不变的,论证了临夏台钻孔系统基本上满足了叠加性、齐次性与时不变性,基本上为一线性时不变系统. 相似文献
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井水位观测系统作为一种天然的体应变计,我们可以把固体潮理论值作为观测井的输入值,以维尼迪可夫调和分析结果的半日波M2波群的振幅比作为井水位观测系统的灵敏度,其倒数即为观测格值,然后就可将井水位观测转换成体应变值。本文以汤坑井为例,计算分析了由印尼远震、汶川地震、台湾地震共三种地震类型对汤坑井水位所激励的水震波,结果显示,所记录到的水震波是叠加在体应变固体潮背景上的一种阶跃,对三种地震类型都分别做出了不同程度的响应,体应变固体潮响应幅度最高可达10^-7,体应变响应幅度与地震能量成正比,响应延迟时间与震中距成正比。 相似文献
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2019年长宁M6.0地震和2018年兴文M5.7地震引起了华蓥山断裂及其附近区域8口观测井水位不同程度的响应变化。 本文对比分析各观测井水位的同震响应特征, 从地震波能量密度、 同震破裂体应变、 含水层渗透性参数变化以及断裂带控制作用几个方面探讨了其同震响应机理。 结果显示, 井水位同震响应的幅度与地震波能量密度有一定关系; 2019年长宁M6.0地震引起的井水位同震响应形态符合同震破裂体应变四象限空间分布特征, 但2018年兴文M5.7地震则不符合; 两次地震引起的含水层渗透性参数变化存在空间上的不一致性和单点各向异性, 并且断裂带自身的水文条件对井水位同震响应形态和幅度有一定的控制作用。 综合分析认为, 目前已有的几种机理无法完全解释两次地震引起的井水位同震响应现象。 相似文献
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雷暴产生的气压突变对体应变与同井水位干扰的对比研究 总被引:2,自引:0,他引:2
对首都圈地区涞水台等Sacks体应变与同井水位数字化分钟值观测数据进行对比研究,发现在雷暴时段二者潮汐观测曲线会发生同步显著畸变异常。经小波分析、回归分析和功率谱分析,并与气压资料比对,证实这是由于雷暴引发了气压瞬间突变而产生的干扰,其幅值比背景值分别高近8倍和11倍,这种现象主要集中在雷雨季节的6~8月。进一步研究了周期气压波对体应变与井水位的影响规律和机制,并将雷暴日与无雷日气压对体应变和井水位的影响系数曲线进行了比较,总结了它们之间的差异和特征。 相似文献
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水井潮汐观测资料的分析 总被引:1,自引:0,他引:1
对全国地下水观测网中33口井孔的水位和气压观测资料,采用反复调和分析的方法,求出了井水位固体潮体应变各分波群的潮汐系数和位相滞后,求出了井水位气压各分波群的气压系数和位相滞后。对这些结果作了初步分析和讨论。 相似文献
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体应变观测中的气压干扰机制和作方法的研究 总被引:4,自引:0,他引:4
建立体应变理论气压干扰模型,通过实际观测资料研究了气压对体应变月变和日变的干扰过程,探讨消除干扰的方法,且和水位资料作了对比分析。 相似文献
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九江地震台洞体应变观测环境影响分析 总被引:1,自引:1,他引:0
对九江地震台2008—2013年洞体温度年变化、气压上升、集中降雨、抽水和承压含水层卸载对洞体应变产生的异常进行统计,获得应变异常量级范围,建立洞体应变观测简单静力学模型。研究认为,九江地震台山洞线应变年变化由观测基线介质的温度效应引起,而气压、降雨、抽水和含水层卸载引起的应变变化则主要由山体附加应力决定。 相似文献
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分时段研究降雨、钻孔水位、工程施工等因素对青岛地震台体应变的影响,研究结果表明:钻孔水位反映区域地下水主要由降雨补给,降雨下渗改变地下水状态,并影响体应变观测;青岛体应变与钻孔水位的相关性及其周期特性均在2015年前后出现变化,可能与2015—2016年降雨偏少及工程施工有关;2018年1月17日台站钻孔施工很可能改变了体应变周围岩石孔隙环境,并扩大孔隙压力作用系数,可解释2018年3月以来水位小幅上升引起的体应变显著压性上升现象,受钻孔施工的影响,体应变与钻孔水位相关性的滞后特征明显减弱。 相似文献
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INFLUENCE OF PUMPING ON FOUR-COMPONENT BOREHOLE STRAIN AT TAI'AN SEISMIC STATION AND ITS INTERFERENCE MECHANISM
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JIA Yuan GAN Wei-jun LI Jie ZHU Cheng-lin YIN Hai-tao LU Shuang-ling JU Jia-bin 《地震地质》2019,41(6):1429-1443
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=1.217arctan(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 station, we take a known pumping as an example, in which we study the principal strain state of the borehole in three periods of normal pumping, interruption of pumping and resuming pumping respectively. During each period, we solve 3 parameters of the principal plane strain state, i.e. the maximum principal strain rate, the minimum principal strain rate and the maximum principal strain direction from four observation equations of FCBS by nonlinear iterative least squares algorithm. On the other hand, concentrated load model (CLM) is used to simulate the mechanical mechanism of pumping. Firstly, the depth of FCBS relative to pumping source and the concentrated load at pumping source are inversed, then, the strain state surrounding the pumping well, including the state at RZB-3 borehole, is simulated by forward modeling. By comparing these results, we find that:
(1)The concentrated load at pumping source inversed by CLM during periods of normal pumping and resuming pumping are both located at or near the bottom of the pumping well, which is consistent with the actual situation, indicating that mechanism and degree of the influence of pumping on borehole strain are well simulated by CLM.
(2)The observed strain state is consistent with the simulation result of pumping interference by forward modeling, indicating that the principal strain state of borehole calculated based on observation of FCBS reflects the true strain state of borehole under different pumping states.(3)The inversed concentrated load at pumping source during pumping periods is significant greater than the load of the pumped water, indicating that the pumping process has more significant influence on the pore pressure of rocks than the load of the pumped water.
Even though CLM is an approximate simulation since it's based on some elastic assumptions, the interference mechanism of pumping on RZB-3 type FCBS at Tai'an seismic station is well explained, which is maybe very helpful for studying the influence of pumping interference on other deformation instruments, locating the unknown pumping source and studying the characteristics of pore pressure of rocks. 相似文献
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根据潮汐因子计算结果,确定了井水位观测格值。又由线应变和水位与体应变转换公式,分别计算了在固体潮、大气压、强远震和承压含水层排水作用下伸缩仪与水位仪的的体应变响应量,二者相对变化率(体应变比值)在0.242~0.668之间,分析比较了二者的响应特征,并初步解释了水位与应变同步变化的物理机制。 相似文献
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