Epicenter location by abnormal ULF electromagnetic emissions

Abstract

The epicenter location before earthquake is very important. We investigated the characteristics of the ULF electromagnetic emissions, which were observed by an east-west chain at Kashi, Anxi, and Beijing stations before the ML = 7.1 Hertian earthquake, Xingjiang, China, on November 19, 1996. We define the polarization angle as the angle between the east direction of the geomagnetic field and the major axis of the polarization ellipse, which is obtained by the filtered data of two horizontal components. The source of ULF electromagnetic emissions before earthquake is probably coming from the direction perpendicularly to the polarization major axis of earthquake related emissions. We located the source as the cross of two source directions that were obtained at Kashi and Anxi station on November 18, 1996. The estimated source is consistent with the epicenter of the Hetian event.