【摘要】：觀測和實驗結(jié)果表明,在強震和大型地質(zhì)災害孕育和發(fā)生過程中,地電阻率及其各向異性會出現(xiàn)明顯的異常變化,因此電阻率一直是我國地震監(jiān)測預報中使用的重要參量之一,在近50年來的地震監(jiān)測預報工作中發(fā)揮了重要作用。震例研究表明,在某些強震前,利用目前地震電阻率觀測中僅有4個固定電極的對稱四極測量系統(tǒng),即使在離震中很近的臺站,并不是所有測向上都能記錄到明顯的地電阻率異常變化,這可能導致地震異常誤判的幾率。因此,探索新的地震電阻率觀測方式,可以為目前地震電阻率觀測系統(tǒng)提供有益的補充,這對我國的防震減災具有實際意義。本文將借鑒已經(jīng)在物探領域非常成熟的電阻率層析成像技術來進行巖石電阻率圖像及各向異性動態(tài)變化的實驗研究。在單軸固定速率加、卸載下,獲得不同應力下的電阻率圖像及電阻率各向異性圖,研究它們隨應力的變化規(guī)律和特征,依此探討電阻率圖像及各向異性異常變化作為地震異常的可能性。在對相對均勻(樣品Ⅰ)、內(nèi)嵌高阻(樣品Ⅱ、Ⅲ)和內(nèi)嵌低阻(樣品Ⅳ、Ⅴ)的5組人工樣品實施單軸壓縮和卸載過程中,利用電阻層析成像方法構(gòu)建了在樣品自由表面以中心點對稱布設的4條輻射狀測線的視電阻率相對變化(以下稱為RRC)圖像,并計算和作出了表征裂隙產(chǎn)生和/或發(fā)展速率的視電阻率各向異性系數(shù)λ*以及表征裂隙產(chǎn)生和/或發(fā)展方位的各向異性主軸方位角a隨應力和深度的變化曲線。結(jié)果表明,(1)所有測線對應的RRC圖像隨著應力都呈現(xiàn)出了相同的變化趨勢：隨著應力的增加,RRC圖像中電阻率降低的區(qū)域(以下稱為RDR區(qū))逐漸收縮,而同時電阻率升高的區(qū)域(以下稱為RIR區(qū))逐漸擴張；在卸載階段,隨著應力的減小,RIR區(qū)繼續(xù)擴張,而RDR區(qū)繼續(xù)收縮。(2)樣品中的高、低阻體對其所在部位和附近區(qū)域的電阻率值增加的幅度有較大影響,但都對電阻率圖像的趨勢性變化沒有影響。(3)對于原始電性各向異性的樣品,裂隙主要在巖樣的淺部產(chǎn)生和/或發(fā)展,而在較深的部位裂隙產(chǎn)生和/或發(fā)展的速率相對較低。本文的實驗結(jié)果揭示出巖石電阻率圖像及各向異性隨應力均呈現(xiàn)出了規(guī)律性的異常變化,這表明電阻率圖像及其各向異性異常變化可以作為地震異常。
[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，

本文編號：2505136