摘要
Through fitting and monthly-anomaly analysis of the monthly mean value of the relative geomagnetic Z-component at Thonghai station since 1986, the authors find an evident variation of velocity of Z-component—accelerated rise or fall before the M≥6.0 earthquakes in Yunnan Province. From March 2009 to June 2010,the velocity of Z-component acceleratedly rose for 48.5 nT and the duration lasted for 15 months. According to the statistics of earthquake cases in Yunnan Province and the earthquake-prediction indexes, it is concluded that there exists a risk of earthquake with M6.0 or even M7.0 in one year or some time longer.