共查询到19条相似文献，搜索用时 281 毫秒
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介绍宝鸡深井地电阻率的装置系统及各道测值的趋势变化特征。采用统计和降雨量褶积的方法,分析了降雨和地下水位等影响因素,结果显示:短期强降雨会造成各道数据的同步下降趋势,由于电极布设的原因,第3道受降雨影响下降程度略大于第2道;各道测值长趋势的变化并非降雨因素主导。采用相关性分析和数值模拟的方法对地下水位变动进行了分析,发现地下水位虽然与第2道测值的趋势存在相关性,但数值模拟结果显示宝鸡深井地电阻率各道趋势变化与地下水位无关。 相似文献
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汶川MS8.0地震前, 位于震源区内的成都台NE测线地电阻率显示了数年大幅度趋势下降异常, 其年变化甚至严重畸变到消失的程度, 它和多年来我国7级以上大地震记录到的异常形态有极大的相似性, 被认为是最清晰的异常之一. 然而, 长期的观测表明, 成都台NE测线地电阻率与测区潜水水位年变化呈正相关. 因此, 关注异常发展过程中测区水位变化, 成为汶川MS8.0地震震例地电阻率异常科学总结的重要课题之一. 本文通过对成都台建台以来NE测线地电阻率的全程分析, 确认与汶川MS8.0地震有关的地电阻率异常变化属于全程变化的第三阶段(1999—2008年). 分析了第三阶段同步观测的地下水位数据, 并进行了地电阻率和地下水位趋势变化的综合分析. 最终确认与汶川MS8.0地震有关的地电阻率异常经历了前、 后两个时段: 前期2004年2月—2006年2月, 小幅趋势上升, 幅度约为1.9％; 后期2006年2月—2008年2月, 趋势下降, 幅度达-6.8％, 如此大幅度快速下降现象, 是成都台建台30多年来从未见到的. 基于前人开展的试验工作的启示, 推测与此下降相应的测区底层(h＞96.6 m)介质电阻率减小量可达22.3％左右. 其量级之大, 须用承载标本试验中岩石破裂前微裂隙广泛发育和排列趋同化导致的地电阻率变化来解释, 由于成都台位于汶川地震震源区内的特殊位置, 可以作为汶川地震孕震物理过程研究中的重要约束条件之一. 相似文献
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为了深入研究地电阻率1年尺度以上趋势变化的区域性和同步性,本文从地电阻率与水位、水准的关系以及地电阻率固体潮现象的角度,通过理论、实验、实例分析了地电阻率趋势变化产生的原因.分析结果显示,地电阻率趋势变化与观测系统或水位(非构造水位)无关,而与周围构造变化有关,且趋势上升和下降分别反映了周围应力场的压性和张性变化.在此基础上,以高邮台和成都台为例,从地电阻率与周围地震的关系分析了地电阻率趋势变化的场兆特征,结果表明地电阻率在上升趋势转折时更具有短期的预测意义.本文结果可以为研究地电阻率的长期趋势变化现象提供参考; 未来地震的预测需在综合各台站观测结果的基础上才能有效地判定区域应力场的方向和相对幅度,从而给出有意义的地震前兆预测结果. 相似文献
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初步分析乌鲁木齐地区1 990年后发生的9个地震前后地电阻率的变化特征,发现:地电阻率观测值曲线在地震前几个月开始下降.用月距平法分析消除地下水位、温度、气压和降雨对地电阻率的影响,对其前兆异常加以验证,可见震前短临异常变化明显. 相似文献
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本文基于测深反演结果, 通过数值模拟定性分析了地下水位和降雨对周至地电台地电阻率观测的影响; 同时利用褶积算法定量分析了降雨对该台NS向和NE向地电阻率观测的短期影响和长趋势影响.结果表明, 周至地电台地电阻率年变主要由地表薄层介质电阻率季节变化引起, 受地下水位变化影响不明显. 降雨对NS向和NE向地电阻率观测值的影响在短期内与观测结果一致, 表现为增加; 但长期趋势则与观测结果呈负相关关系.根据数值模拟分析认为, 这种变化与降雨及其渗透深度有关.分析结果与实际观测结果一致, 为正确认识周至地电台地电阻率观测与异常判定提供合理的理论依据. 相似文献
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本文通过河北省隆尧县大柏舍地电台不同供电极距试验观测资料,与地下潜水水位动态的相关分析及数学模型计算结果,给出地电阻率年变化的一种物理解释,即认为大柏舍台地电阻率年变化是由于供电极距短,勘探深度浅,从而受潜水动态影响的结果。为消除大柏舍台地电阻率年变化,应采用不小于1500米的供电装置。 相似文献
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本文以三层电剖面模型计算出由于电剖面参数变化而引起的视电阻率变化,进而说明因地下水位变化所引起的视电阻率变化是可能估计的。根据这个结果能够确定出由于地下水干扰所引起的视电阻率异常幅度,这将有利于视电阻率变化与地震关系的定性、定量分析研究。实际工作表明,视电阻率变化很复杂,许多因素都会使视电阻率发生变化,但水的影响很重要,因此,研究这个问题有重要意义。 相似文献
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针对宝鸡地震台地电阻率在每年的6~8月份出现明显变化的现象,在环境、气象等因素调查的基础上,利用水平介质模型反演该台电性分层结构,计算了地下水位变化对其视电阻率的影响,认为主要是6~8月份,该台站测区浅表水位的明显下降变化直接或间接造成了地电阻率的变化。 相似文献
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The paper focuses on defining the performance and limits of ERI in the detection and sedimentary characterization of near-bottom thin layers. The analysis of the resolution of floating and submerged cables, and the effect of the accuracy of a priori information (resistivity and thickness) in the data inversion, is based on theory, models and actual data. Theoretical models show that the actual reconstruction of the near water-bottom sediments, in terms of geometry and resistivity, can be obtained only with the submerged cable, however, the data, unlike that acquired with the floating cable, require a priori information on water resistivity and thickness for the data inversion. Theoretical forward models based on wrong a priori water thickness and resistivity information influence the inverted model in different ways, depending on the under- and over-estimation of water resistivity and thickness, and the resistivity contrast of the water–solid layer; however a water–solid resistivity contrast of less than 2 and within 10% of error in water resistivity has no effect. Overestimating water resistivity depicts a ground similar to the actual ground in terms of resistivity, more so than the underestimation of water resistivity. Moreover, the data inversion is less influenced by water parameter error in the case of low resistivity contrast in the water–solid layer, than it is for high resistivity contrast. Wenner and Schlumberger arrays give comparable results, while a dipole–dipole array seems to be more sensitive to the accuracy of apparent resistivity measurements and a priori information on water.The theoretical considerations were validated by actual data acquired with a submerged cable on the Tiber River. The study has shown that if highly accurate measurements are made of water thickness and resistivity, then electrical resistivity imaging from the submerged cable can be used in addition to, or even to substitute, seismic data for the reconstruction of the features and sedimentary characterization of near-bed sediments where seismic data fail to give a suitable resolution. 相似文献
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Parts of the consecutive apparent resistivity monitoring stations of China have recorded clear diurnal variations. The relative amplitudes of diurnal variations at these stations range from 1.3‰ to 5.8‰. The daily accuracies of apparent resistivity observation are better than 1‰, because the background electromagnetic noise is rather low at these stations. Therefore, the diurnal variations of apparent resistivity recorded at these stations are real phenomena. The diurnal variation shapes can be divided into two opposite types according to their characteristics. One type is that the apparent resistivity data decreases during the daytime but increases during the nighttime(Type 1). The other type is the apparent resistivity data increases during the daytime but decreases during the nighttime(Type 2). There is a correspondence between the diurnal and annual variation patterns of apparent resistivity. For the monitoring direction with diurnal variation of Type 1, the apparent resistivity decreases in summer and increases in winter. However, for the monitoring direction with diurnal variation of Type 2, the apparent resistivity increases in summer and decreases in winter.
We take an analysis on the mechanism of apparent resistivity diurnal variation, combining the influence factors of water-bearing medium's resistivity, the electric structure of stations, and the apparent resistivity sensitivity coefficient(SC)theory. Intuitively, diurnal variation of apparent resistivity is caused by diurnal variation of medium resistivity in the measured area. The diurnal variation of medium resistivity will inevitably be caused by the factors with diurnal variation. Among the possible factors, there is diural variation in earth tide and temperature.
Our analysis displays that apparent resistivity diurnal variation is not caused by the usually-believed earth tide, but by the ground temperature difference between daytime and nighttime. The earth tide strain is too small to cause remarkable effects on the apparent resistivity data. On the other hand, the daily tide strain has two peak-valley variations, and its phase and amplitude has a period of approximate 28 days. However, the apparent resistivity data do not show these corresponding features to earth tide. Furthermore, the detection range of current apparent resistivity stations is within a depth of several hundred meters. Within this depth range, the medium deformation caused by solid tide can be regarded as uniform change. Therefore, all monitoring directions and all stations will have the same pattern of diurnal variation.
In general, the temperature increases in the daytime but decreases in the nighttime. For most water-bearing rock and soil medium, its resistivity decreases as temperature increases and increases as temperature decreases. Diurnal temperature difference affects about 0.4m of soil depth. Therefore, resistivity of this surface thin soil layer decreases in the daytime while increases in the nighttime. Under layered medium model, SC of each layer represents its contribution to the apparent resistivity. For the stations with positive SC of surface layer, apparent resistivity decreases in the daytime but increases in the nighttime. While for the stations with negative SC of surface layer, apparent resistivity diurnal variations display the opposite shape. 相似文献
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多年观测数据表明,代县地电阻率年变受降雨影响比较显著,通过褶积滤波法获取降雨量对视电阻率的影响值,定量分析降雨与视电阻率的相关性。在此基础上,利用代县地电阻率电测深数据及相关地质资料,建立三维有限元模型,模拟降雨对地电阻率的影响,进一步确定降雨对视电阻率影响的物理机制。结果表明:降雨是造成代县地电阻率年变的主要因素,且与视电阻率呈正相关性;降雨造成表层介质含水饱和度发生变化,使得相应电阻率下降近10倍,从而引起地电阻率年变幅度发生近1/10的改变。 相似文献