Earth Planets Space, Vol. 58 (No. 12), pp. 1611-1615, 2006LETTER
Yoshihisa Iio1, Hiroshi Katao1, Tomotake Ueno1, Bogdan Enescu1, Norio Hirano1, Tomomi Okada2, Naoki Uchida2, Satoshi Matsumoto3, Takeshi Matsushima3, Kenji Uehira3, and Hiroshi Shimizu3
1Research Center for Earthquake Prediction, Disaster Prevention Research Institute, Kyoto University, Gokasho Uji 611-0011, Japan
2Research Center for Prediction of Earthquakes and Volcanic Eruptions, Graduate School of Science, Tohoku University, Aoba-ku, Sendai, Miyagi 980-8578, Japan
3Institute of Seismology and Volcanology, Faculty of Sciences, Kyushu University, Shin'yama, Shimabara, Nagasaki 855-0843, Japan
(Received October 15, 2005; Revised June 9, 2006; Accepted June 13, 2006; Online published February 2, 2007)
We investigated the spatial distribution of static stress drops of the aftershocks of the 2005 West Off Fukuoka Prefecture earthquake, with the aim of assessing the possibility that another earthquake will occur on the SE extension of the earthquake fault. The waveforms from six temporary online telemetry stations installed in and around the aftershock region were measured. Small stress drops were estimated for the aftershocks that occurred relatively distant from the SE and NE ends of the earthquake fault. Conversely, the aftershocks that occurred around the SE end of aftershock region are characterized by large stress drops. These results imply the possibility of a stress concentration at the SE edge of the main shock fault.
Key words: Stress drop, aftershock, site effect, intraplate earthquake, anelastic attenuation, stress.