HR: 0830h
AN: S51A-02    [Abstracts]
TI: High-resolution Image of Aftershock Activity of the 2004 Niigata Chuetsu Earthquake (M6.8)
AU: * Enescu, B
EM: benescu@rcep.dpri.kyoto-u.ac.jp
AF: Research Center for Earthquake Prediction, Disaster Prevention Research Inst., Kyoto Univ., Gokasho, Uji, Kyoto, 611-0011 Japan
AU: Mori, J
AF: Research Center for Earthquake Prediction, Disaster Prevention Research Inst., Kyoto Univ., Gokasho, Uji, Kyoto, 611-0011 Japan
AU: Shibutani, T
AF: Research Center for Earthquake Prediction, Disaster Prevention Research Inst., Kyoto Univ., Gokasho, Uji, Kyoto, 611-0011 Japan
AU: Iio, Y
AF: Research Center for Earthquake Prediction, Disaster Prevention Research Inst., Kyoto Univ., Gokasho, Uji, Kyoto, 611-0011 Japan
AU: Matsushima, T
AF: Inst. of Seismology and Volcanology, Faculty of Sciences, Kyushu Univ., Shin'yama, Shimabara, Nagasaki, 855-0843 Japan
AU: Uehira, K
AF: Inst. of Seismology and Volcanology, Faculty of Sciences, Kyushu Univ., Shin'yama, Shimabara, Nagasaki, 855-0843 Japan
AB: The 23 October 2004 Chuetsu earthquake (M6.8) was followed by intense aftershock activity, which included the occurrence of four events with M ≥ 6.0. In order to analyse in detail the spatial and temporal characteristics of this earthquake sequence, we first determined accurate hypocenter locations using the double-difference algorithm (Waldhauser and Ellsworth, 2000). The relocated events show an increased spatial clustering. One can recognise at least three main fault-like structures, which are clearly defined by the aftershock distribution. About three days after the mainshock the seismic activity extended to the NW and SE. One of the large aftershocks (M6.1), which occurred to the SE, was preceded by few small events. The seismic activity of each cluster of aftershocks is analysed for its frequency-magnitude distribution and decay rate of aftershocks. To have a more accurate estimate of the aftershock decay immediately after the mainshock (minutes-hours), we analyse the continuous Hi-Net waveform data at several stations located closely to the aftershock distribution and try to detect as many early aftershocks as possible.
DE: 7200 SEISMOLOGY
DE: 7215 Earthquake parameters
DE: 7230 Seismicity and seismotectonics
SC: Seismology [S]
MN: 2005 Joint Assembly