Possible earthquake electromagnetic precursor anomalies detected by the CSELF network

It is a debated topic if there is any observable precursor anomalies prior to earthquake (EQ hereafter) and if the stronger EQ can be successfully predicted. This paper will present a new EM observation network built in recent years and show a new finding of EM field with the variation of a one-year cycle observed using the network. As an example, the short-term precursor anomalies of apparent resistivity before the Yangbi EQ (Ms=5.1) occurred on March 17, 2017 in Yunnan province will be studied. The observed anomalous phenomena indicate that the anomaly before the EQ can be captured only if a reasonably effective method is used, and it is believed that continuously observed data on the fixed observation network for long time is a effective means for studying anomalies that appeared before earthquakes.