地震前后CT图像的变化  

Electromagnetic Tomogram before and after Earthquake

作　　者：孙次昌[1,2,3,4] 王绪胜 刘庆芳[1,2,3,4] 陶裕录[1,2,3,4] 于萍 冯锐[1,2,3,4] 

机构地区：[1]国家地震局地球物理研究所 [2]北京大学地球物理系 [3]湖南省地震局 [4]国家地震局地震数据信息中心

出　　处：《中国地震》1997年第4期387-393,共7页Earthquake Research in China

摘　　要：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≥４０，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 tomography have been used to monitor the changes of absorption coefficient of electromagnetic wave before and after earthquake for five years at Dahuichang fault since 1992. It has been found that the 3 months before the occurrence of moderately strong earthquake ( M L≥4.0, Δ <210 km),the several special changes in tomography occurred as follows:The mean value of absorption coefficient dropped about 10% compared with the annually decreasing tendency; The mean difference of pixels suddenly decreased and increased in different directions; The entropy of paragenic matrix in a tomogram decrease and the number of low absorption pixel increased. It is inferred that such changes in electromagnetic tomogram are attributed to the variation of rock micro cracks and porosity. Electromagnetic tomography can be studied as a new technique to detect precursors of earthquakes.

关 键 词：层析图像 地震前兆 图像分析 CT 

分 类 号：P315.7[天文地球—地震学]