几乎所有的破坏性地震都是由于板块构造运动产牛的构造地震.板块构造运动会引起大地电性结构的改变,研究两者之间的联系有助于强震预测.借鉴大地电磁测深法,提出采用Robust估计技术计算地震台站长周期视电阻率的方法,并采用数值试验模型对方法的灵敏度进行了验证.用文中提出的方法对安丘地震台站多年连续观测的长周期大地电磁数据进行了处理,获得了视电阻率曲线,同时提取了多个频点的视电阻率时间序列,发现沂沐断裂带北段深部电阻率随时间变化逐渐升高.台站附近的GPS基线资料也揭示了断裂带两侧位移变小,视电阻率时间序列结果与GPS观测地表形变具有很好的一致性.这与岩石力学实验中高温高压下,深部岩石(上地幔)受压会造成电阻率升高的结论是一致的.文中所述的方法对研究强震电磁前兆和强震预测具有参考价值.%Almost all the destructive earthquakes,so called tectonic earthquake,are produced by tectonic movement.The tectonic movement will cause resistivity changes in the earth.It's valuable for strong earthquake forecast to study the relationship between the resistivity change and tectonic movement.According to magnetotelluric sounding method,we establish a robust estimate method to calculate the long-term apparent resistivity from seismic station monitoring data.We first use 1D layered earth models to test the sensitivity of this method.Then we process the continually observed long term electromagnetic data in 4 years(from 2011 to 2014)from Anqiu seismic station which is very close to the north section of Yishu fault zone.The apparent resistivity curves and the apparent resistivity time series for different frequencies are obtained.The time series show the resistivity increase in the selected 4 years,which is in good agreement with the GPS baseline data.This also satisfies the results from rock mechanics experiments on deep rocks (upper mantle)that the resistivity will increase with improved stress in a high temperature and pressure environment.The method is valuable for studying electromagnetic precursor of strong earthquakes and strong earthquake prediction.
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