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Gao S.-D.,Lanzhou Institute of Earthquake Research | Tang J.,China Earthquake Administration | Sun W.-H.,China Earthquake Administration
Chinese Journal of Geophysics (Acta Geophysica Sinica)

In this paper we analysed the electromagnetic anomaly phenomena related to the March 10 Yingjiang MS5.8 and March 24 Myanmar MS7.2 earthquake occurred in 2011. The anomalies of electromagnetic data are observed in Yunnan Tonghai stations in October 2010 to March 2011. The relationship between the electromagnetic anomaly phenomena and the earthquake events is studied. The following results are obtained: (1)The pulse cluster anomalies of power spectrum density (PSD) of magnetic fields in frequency band of 470~1 Hz appeared before Yingjiang MS5.8 and Myanmar MS7.2 earthquakes. The anomaly of magnetic PSD is about 1~3 orders of magnitude stronger than background field. The anomaly PSD have a close relationship with orientation of electrodes at observed point and the signal frequency. (2) The anomalies were emerged from deep to shallow in the earth's crust at Yingjiang earthquake on March 10, 2011. At first, the resistivity in the depth of 2.6 km began to change 25 days before the earthquake, and at the depth of 400 meters the resistivity changed 10 days before, and the impedance phase changed synchronously. For the Myanmar MS7.2 earthquake of March 24, 2011, the deep and shallow resistivity and impedance phase synchronously changed 10 days before the earthquake, this may be the characteristic of strong earthquakes. Source

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