TY - JOUR
T1 - A precursory ULF signature for the Chi-Chi earthquake in Taiwan
AU - Akinaga, Y.
AU - Hayakawa, M.
AU - Liu, J. Y.
AU - Yumoto, K.
AU - Hattori, K.
PY - 2001
Y1 - 2001
N2 - 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.
AB - 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.
UR - http://www.scopus.com/inward/record.url?scp=0013109051&partnerID=8YFLogxK
U2 - 10.5194/nhess-1-33-2001
DO - 10.5194/nhess-1-33-2001
M3 - 期刊論文
AN - SCOPUS:0013109051
SN - 1561-8633
VL - 1
SP - 33
EP - 36
JO - Natural Hazards and Earth System Sciences
JF - Natural Hazards and Earth System Sciences
IS - 1-2
ER -