| Volumes and Issues Contents of Issue 1/2 Special Issue |
www.nat-hazards-earth-syst-sci.net/1/33/2001/
© Author(s) 2001. This work is licensed
under a Creative Commons License.
A precursory ULF signature for the Chi-Chi earthquake in Taiwan
1Dept. of Electronic Engineering, The University of Electro-Communications, 1-5-1 Chofugaoka, Chofu Tokyo 182-8585, Japan
2Institute of Space Science, National Central University, Chung-Li 320, Taiwan
3Dept. of Earth and Planetary Sciences, Kyushu University, 33 Hakozaki Fukuoka 812-8581, Japan
4Marine Biosystems Research Center, Chiba University, 1-33 Yayoi, Inage Chiba 263-8522, Japan
Abstract. ULF emission data at Lunping (epicentral distance, 120 km) have been analysed for the Chi-Chi earthquake (with magnitude 7.6 and depth of 11 km) in Taiwan which occurred on 21 September 1999. Simple intensity analyses have not yielded any significant results but we have found, based on the analysis of polarization (the ratio of vertical magnetic field component Z to the horizontal component G), that the polarization (Z/G) showed a significant enhancement for two months before the earthquake. This kind of temporal evolution of polarization seems to be very similar to previous results, so that it is highly likely that this phenomenon may be associated with the Chi-Chi earthquake. Also, the comparison of the results of polarization analyses, by changing the signal threshold, has given us an approximate intensity of the seismogenic emission of the order of the monthly mean value.
Full Article (PDF, 155 KB)
Citation: Akinaga, Y., Hayakawa, M., Liu, J. Y., Yumoto, K., and Hattori, K.: A precursory ULF signature for the Chi-Chi earthquake in Taiwan, Nat. Hazards Earth Syst. Sci., 1, 33-36, 2001. Bibtex EndNote Reference Manager
