Continuous operation of seismic ACROSS for the past 5 years; Review and preview

Kunitomo, Takahiro; Hasegawa, Ken; Kumazawa, Mineo

Continuous test operation of seismic ACROSS was made to establish a routine technology for the underground study. (1) The transmitted signals in 10-20 Hz have been detected with S/N=10 by Hi-net stations located to 100 km by data stacking of 3 years. Signal level detected is in the order of 10 m in displacement amplitude. (2) Results of moving data stacking of one week or month reveal various types of temporal variations with a level marginal to the observational errors at many stations. We recognize the necessity of further strategy to identify each of temporal variations. Discussion is made on the targets in the forthcoming years after the 5 year test operation; (a) the trial test monitoring of the shaft excavation at Mizunami Underground Research Laboratory, (b) development of ACROSS technology to fulfill the social and academic needs and (c) monitoring study of the expected fault plane of coming Tokai Earthquake.