SEGJ Technical Conference

Time variation of wave phases in the seismic transfer function between Toki and Hourai using seismic ACROSS

Abstract We have been studying the long-term continuous monitoring of seismological processes occuring at and around the plate boundaries using ACROSS, Accurately Controlled and Routinely Operated Signal System. So far, using the Toki ACROSS source and the seismic array deployed around the Hi-net Hourai station, the waves reflected from deep subsurface including the plate boundary were extracted and their temporary variations were investigated. In this study, we used the Hi-net data from Jan. 2005 to Mar. 2007 and exermined the time-variation of the wave phases in the Hzr and Htt components of the transfer functions with respect to the cross-correlation coefficient, the travel-time and the square sum of the amplitude. The result shows a remarkable stability and a high reliablity of the ACROSS. The time-variation shows seasonal variation and magnified at the later phases than the first arrival. The synchonicity with the activity of deep low-frequency tremors is anticipated, however, still remains unproven.