Detection of ULF electromagnetic emissions as a precursor to an earthquake in China with an improved polarization analysis
- 1Department of Electronic Engineering and Research Station on Seismo Electromagnetics, The University of Electro-Communications, 1-5-1 Chofugaoka, Chofu, Tokyo, 182-8585, Japan
- 2Institute of Geophysics, China Earthquake Administration, Beijing 100081, China
- 3Kashi Observatory, Earthquake Administration of Xinjiang Uygur Autonomous Region, Xinjiang 844000, China
Abstract. An improved analysis of polarization (as the ratio of vertical magnetic field component to the horizontal one) has been developed, and applied to the approximately four years data (from 1 March 2003 to 31 December 2006) observed at Kashi station in China. It is concluded that the polarization ratio has exhibited an apparent increase only just before the earthquake on 1 September 2003 (magnitude = 6.1 and epicentral distance of 116 km).