2022年青海门源M_(S)6.9地震前地电阻率变化分析

Analysis of Earth Resistivity Changes before the 2022 Qinghai Menyuan M_(S)6.9 Earthquake

分别运用原始曲线分析法和归一化速率方法分析门源地震震中300 km范围内3个地电阻率台站数据变化。从原始曲线来看,金银滩台EW道临震前2个月出现大幅突跳及保留年变形态的趋势下降(-3.3%);山丹台NS道趋势下降(-1.9%)、EW道趋势上升(3.1%);武威小西沟台NS道趋势下降(-3.3%)、EW道趋势上升(2.8%),震后EW道趋势转平。而3个地电阻率台站归一化速率曲线在门源地震前均出现超过阈值的现象,但各自归一化速率形态存在差异。整点值突跳变化和日均值、月均值曲线加速变化、转折变化,尤其是上升至高值阶段出现的转折变化均可作为异常形态进行分析,以上变化不明显时需结合归一化速率方法提取异常。

We use the original curve analysis and normalized rate method to analyze the changes of three earth resistivity data sets within 300 km from the epicenter of Menyuan earthquake.Judging from the original curve,the EW component of Jinyintan station has a sharp jump and a downward trend of retaining annual change(-3.3%)in the two months before the earthquake.The NS component of Shandan station has a downward trend(-1.9%),and the EW component has an upward trend(3.1%).The NS component of Wuwei Xiaoxigou station has a downward trend(-3.3%),the EW component has an upward trend(2.8%),and the trend of EW component turned flat after the earthquake.The normalized rate curves of the three earth resistivity stations all exceeded the threshold before the Menyuan earthquake,but their normalized rate patterns are different.The sudden change of the hour value,the accelerated change of the daily average and monthly average values,and the turning change,especially the turning change in the stage of rising to the high value,which can be analyzed as an abnormal shape.When the above changes are not obvious,the normalized rate method should be combined to extract the abnormality.