Earth Planets Space, Vol. 58 (No. 12), pp. 1627-1632, 2006LETTER
Satoshi Matsumoto1, Atsushi Watanabe1, Takeshi Matsushima1, Hiroki Miyamachi2, and Syuichiro Hirano2
1Institute of Seismology and Volcanology, Faculty of Sciences, Kyushu University, Shimabara, Japan
2Faculty of Science, Kagoshima University, Kagoshima, Japan
(Received August 19, 2005; Revised February 3, 2006; Accepted February 14, 2006; Online published February 2, 2007)
Spatial distribution of S-wave scatterers in the SE part of the focal area of the 2005 West Off Fukuoka Prefecture Earthquake (M = 7.0) has been estimated using dense seismic array data. Waveforms of 22 natural earthquakes were analyzed in a frequency range of 16-24 Hz. It is difficult to estimate the inhomogeneous structure in this wavelength range with ordinary travel time tomography despite the importance of this parameter for understanding the earthquake-generating process. After filtering and gain recovery in the coda part, observed waveforms were semblance-enhanced slant-stacked into various directions from the array. This was followed by diffraction curve summation in order to image the scatterer distribution. The spatial distribution of scatterers thus imaged revealed that higher strengths were distributed at the SE-extension of the fault plane of the event, which corresponds to a region where the rupture process of the main shock stopped.
Key words: Scatterer, seismic array, 2005 West off Fukuoka Prefecture earthquake.