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采用井间电磁波ＣＴ技术，对大灰厂断层进行了５年定期监测，发现中强震（ＭＬ≥４０，震中距Δ＜２１０ｋｍ）发生前３个月左右，ＣＴ图像出现下述变化：吸收系统均值在逐年降低的基本趋势下，进一步下降１０％左右；象素的灰度差分均值在不同方向上突然下降或上升；图像灰度共生矩阵的熵值下降；低吸收象素增多。分析表明，震前岩石裂隙与孔隙结构的变化导致了电磁波ＣＴ图像的变化。电磁波ＣＴ技术有可能作为一种探测地震前兆的新手段。
The cross-well electromagnetic CT technique was used to monitor the fault of a large ash plant for five years. It was found that the following changes occurred in CT images about 3 months before the occurrence of moderately strong earthquakes (ML≥40, epicentral distance Δ <210km): The mean value of the absorption system decreases further by about 10% in the basic trend of decreasing year by year; the average value of the gray difference of the pixels suddenly drops or rises in different directions; the entropy of the image gray level co-occurrence matrix decreases; and the number of low absorption pixels increases. The analysis shows that the change of rock fracture and pore structure before the earthquake leads to the change of electromagnetic CT images. Electromagnetic wave CT technology may serve as a new means of detecting seismic precursors.