SEGJ Technical Conference

Time Lapse experiment using the seismic ACROSS source near the Nojima-fault in Awaji Island - 2

Abstract In February and March, 2011, we conducted the time-lapse experiment in Awaji Island using two different types of ACROSS sources: with the horizontal rotational and vertical rotational axes. The latter is called NagoyaUniv. ACROSS source in this paper. We injected 80 tons air in total amount into the 100-m depth point of the Osaka formation. We installed 32 3-component geophone sets at the surface. This article mainly describes the preliminary results obtained by the Nagoya-Univ. ACROSS source. The results showed very clear changes of waveforms immediately after the injection of air except #7 station. The 800-m borehole seismometers also showed the clear change at the initiation of injection. The changes are larger and clearer for the later phases of S waves.