Generation mechanisms of ULF electromagnetic emissions before the ML=7.1 earthquake at Hotan of Xinjiang
新疆和田ML7.1地震前ULF电磁辐射的激发机理

The earthquake M L7.1 took place at Hotan of Xinjiang province on Oct.19, 1996. Three types of Ultralow frequency(ULF) electromagnetic precursors were observed before the earthquake: (1) drift of dynamic zeros, (2) the vertical direction of the major axis of the polarization ellipse orientated to the epicenter, and (3) large amplitude of ULF electromagnetic radiation. A simple model for the generation mechanism of these precursors is proposed. Based on this model, we explain the effect of static electric field inducted by dipole on the variation of voltage and direction of axis on polarization ellipse for horizontal components.