岩石电阻率图像及各向异性变化的实验研究 |
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引用本文: | 张斌,朱涛,周建国. 岩石电阻率图像及各向异性变化的实验研究[J]. 地震学报, 2017, 39(4): 478-494. DOI: 10.11939/jass.2017.04.004 |
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作者姓名: | 张斌 朱涛 周建国 |
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作者单位: | 1.中国北京 100081 中国地震局地球物理研究所 |
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基金项目: | 中央级公益性科研院所基本科研业务专项DQJB13B05国家自然科学基金41574083国家自然科学基金(41574083) 和中央级公益性科研院所基本科研业务专项(DQJB13B05) 共同资助 |
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摘 要: | 在两组人工样品自由表面以中心点为基准对称布设3条辐射状测线,对样品实施单轴应力加载和卸载后,利用电阻率层析成像方法构建了相应的视电阻率相对变化图像,并计算和绘制了表征裂隙产生和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发展方位的各向异性主轴方位角α随应力和深度的变化曲线.结果表明:所有测线所对应的RRC图像均随着应力的变化呈现出相同的变化趋势,即在加载阶段,随着应力的增加,视电阻率相对变化图像中电阻率降低区域逐渐收缩,而电阻率升高区域逐渐扩张,在卸载阶段,随着应力的减小,电阻率降低区域继续收缩,电阻率升高区域继续扩张;样品中的高阻体对其所在部位及附近区域的电阻率增幅有较大影响,而对横越高阻体测线的视电阻率相对变化图像的趋势性变化无影响;对于原始电性为各向异性的样品,随着应力的增加,其各向异性程度降低;裂隙主要在岩样的浅部产生和发展,而在较深部位的裂隙产生和发展的速率相对较低.上述结果有助于解释和理解地震、火山活动和大型地质构造运动引起的视电阻率及其各向异性的变化特征,电阻率层析成像方法可能成为目前地震电阻率观测方法的有益补充.
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关 键 词: | 岩石电阻率 视电阻率相对变化 电阻率层析成像 视电阻率各向异性 |
收稿时间: | 2016-11-30 |
Experimental studies on the changes of rock resistivity image and anisotropy |
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Affiliation: | 1.Institute of Geophysics, China Earthquake Administration, Beijing 100081, China2.Key Laboratory of Seismic Observation and Geophysical Imaging, China Earthquake Administration, Beijing 100081, China |
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Abstract: | Apparent resistivity data was acquired during the uniaxial compression on two sets of man-made samples. Then we constructed the relative resistivity change (RRC) images corresponding to three radial measuring lines intersecting with the center of a sample surface using electrical resistivity tomography, and plotted the curves of apparent resistivity anisotropy factor λ* and azimuthal angle of anisotropy axis α versus stress and depth. λ* and α represent the rate and direction of crack generation and development respectively. Our results indicate that all RRC images show the same change trend with the change of stress. With the increase of stress, the resistivity-decreased region (RDR) in the RRC images would shrink gradually, while the resistivity-increased region (RIR) would expand gradually. During the process of unload-ing, with the decrease of stress, the RIR continues to expand, and RDR conti-nues to shrink. The high-resistivity block embedded in a sample has a great influence on the resistivity-increased amplitude at its location and surroundings, but little effect on the trending change of resistivity image. For the samples with originally electrical anisotropy, λ* decreases with the increase of stress; Cracks appeared and developed mainly in the shallower part of a rock sample, while in the deeper part, the rate of crack generation and development is much lower, which can help to explain and understand the changes in resistivity and its anisotropy caused by earthquakes, volcanic activities and large-scale tectonic movements. This method could be a useful complement to the current seismic resistivity observation methods. |
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