单轴固定速率加、卸载下岩石电阻率图像及各向异性动态变化的实验研究
发布时间：2019-06-24 14:32
【摘要】：观测和实验结果表明,在强震和大型地质灾害孕育和发生过程中,地电阻率及其各向异性会出现明显的异常变化,因此电阻率一直是我国地震监测预报中使用的重要参量之一,在近50年来的地震监测预报工作中发挥了重要作用。震例研究表明,在某些强震前,利用目前地震电阻率观测中仅有4个固定电极的对称四极测量系统,即使在离震中很近的台站,并不是所有测向上都能记录到明显的地电阻率异常变化,这可能导致地震异常误判的几率。因此,探索新的地震电阻率观测方式,可以为目前地震电阻率观测系统提供有益的补充,这对我国的防震减灾具有实际意义。本文将借鉴已经在物探领域非常成熟的电阻率层析成像技术来进行岩石电阻率图像及各向异性动态变化的实验研究。在单轴固定速率加、卸载下,获得不同应力下的电阻率图像及电阻率各向异性图,研究它们随应力的变化规律和特征,依此探讨电阻率图像及各向异性异常变化作为地震异常的可能性。在对相对均匀(样品Ⅰ)、内嵌高阻(样品Ⅱ、Ⅲ)和内嵌低阻(样品Ⅳ、Ⅴ)的5组人工样品实施单轴压缩和卸载过程中,利用电阻层析成像方法构建了在样品自由表面以中心点对称布设的4条辐射状测线的视电阻率相对变化(以下称为RRC)图像,并计算和作出了表征裂隙产生和/或发展速率的视电阻率各向异性系数λ*以及表征裂隙产生和/或发展方位的各向异性主轴方位角a随应力和深度的变化曲线。结果表明,(1)所有测线对应的RRC图像随着应力都呈现出了相同的变化趋势：随着应力的增加,RRC图像中电阻率降低的区域(以下称为RDR区)逐渐收缩,而同时电阻率升高的区域(以下称为RIR区)逐渐扩张；在卸载阶段,随着应力的减小,RIR区继续扩张,而RDR区继续收缩。(2)样品中的高、低阻体对其所在部位和附近区域的电阻率值增加的幅度有较大影响,但都对电阻率图像的趋势性变化没有影响。(3)对于原始电性各向异性的样品,裂隙主要在岩样的浅部产生和/或发展,而在较深的部位裂隙产生和/或发展的速率相对较低。本文的实验结果揭示出岩石电阻率图像及各向异性随应力均呈现出了规律性的异常变化,这表明电阻率图像及其各向异性异常变化可以作为地震异常。
[Abstract]:The observation and experimental results show that there will be obvious abnormal changes in ground resistance and its anisotropy during the preparation and occurrence of strong earthquakes and large geological disasters. Therefore, resistance has always been one of the important parameters used in earthquake monitoring and prediction in China, and has played an important role in earthquake monitoring and prediction in recent 50 years. The earthquake case study shows that before some strong earthquakes, using the symmetrical quadrupole measurement system with only four fixed electrodes in the seismic resistance observation at present, not all the stations very close to the epicenter can record the obvious abnormal variation of geoelectric resistance, which may lead to the probability of misjudgment of seismic anomalies. Therefore, the exploration of new seismic resistance observation methods can provide a useful supplement for the current seismic resistance observation system, which is of practical significance for earthquake prevention and disaster reduction in China. In this paper, the resistance tomography technology, which has been very mature in the field of geophysical exploration, will be used for reference to carry out the experimental study of rock resistance image and anisotropy dynamic change. Under the condition of uniaxial fixed rate addition and unloading, the resistance images and resistance anisotropy diagrams under different stresses are obtained, and their variation laws and characteristics with stress are studied, and the possibility of resistivity images and anisotropy anomalies as seismic anomalies is discussed. In the process of uniaxial compression and unloading of five groups of artificial samples with relatively uniform (sample 鈪，
本文编号：2505136
[Abstract]:The observation and experimental results show that there will be obvious abnormal changes in ground resistance and its anisotropy during the preparation and occurrence of strong earthquakes and large geological disasters. Therefore, resistance has always been one of the important parameters used in earthquake monitoring and prediction in China, and has played an important role in earthquake monitoring and prediction in recent 50 years. The earthquake case study shows that before some strong earthquakes, using the symmetrical quadrupole measurement system with only four fixed electrodes in the seismic resistance observation at present, not all the stations very close to the epicenter can record the obvious abnormal variation of geoelectric resistance, which may lead to the probability of misjudgment of seismic anomalies. Therefore, the exploration of new seismic resistance observation methods can provide a useful supplement for the current seismic resistance observation system, which is of practical significance for earthquake prevention and disaster reduction in China. In this paper, the resistance tomography technology, which has been very mature in the field of geophysical exploration, will be used for reference to carry out the experimental study of rock resistance image and anisotropy dynamic change. Under the condition of uniaxial fixed rate addition and unloading, the resistance images and resistance anisotropy diagrams under different stresses are obtained, and their variation laws and characteristics with stress are studied, and the possibility of resistivity images and anisotropy anomalies as seismic anomalies is discussed. In the process of uniaxial compression and unloading of five groups of artificial samples with relatively uniform (sample 鈪，
本文编号：2505136
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