Anomalous Change Features of Resistivity before the Wenchuan M8.0 Earthquake and Other Large Earthquake in China

The anomalous change features of resistivity in the monitoring stations,which are located near or far from the epicenter of Wenchuan M8.0 earthquake in 2008,are analyzed. There were intermediate-term anomalies for more than one year at Pixian,Ganzi,Mianning and Wudu stations which are less than 400 km from the epicenter,and short and imminent-term anomalies even existed at Lanzhou and Tianshui stations which are far from the epicenter. Also the data of electrical resistivity in past several tens years for 9 large earthquakes with M≥7.0 are summarized. The result shows that most anomalous resistivity changes before large earthquake are negative and the value curves are decline,earthquake often occur near the position of extremum or in resuming process. The anomalies can be found at most stations near epicenter,lasting for more than one year with annual rariation disappear. The short and imminent-term change can be observed also. For far stations,only some have the anomaly,mainly are short and imminent,and event occurs in or after resuming process.