Earth Planets Space, Vol. 60 (No. 11), pp. 1117-1120, 2008LETTER
Disaster Prevention Research Institute, Kyoto University, Japan
(Received October 1, 2007; Revised April 13, 2008; Accepted April 29, 2008; Online published November 18, 2008)
Waveform correlations were used to redetermine P arrival times at 31 stations for a selected set of 321 aftershocks of the 2007 Chuetsu-oki earthquake. These data were used with several different relocation techniques, 1-D velocity structure, 3-D velocity structure using SIMULPS12, 1-D velocity structure using hypoDD, and 3-D velocity structure using tomoDD. The results from all of these methods show a consistent southeast dipping trend for the entire aftershock sequence. The same pattern is also seen for the time period before the largest aftershock. These results indicate that the mainshock fault dips to the southeast.
Key words: Aftershocks, Chuetsu-oki earthquake, fault plane.