Memo on Some Target of Previous Meeting in 2004 and Now

The necessity of deep borehole observation was pointed out in a 2002 WS entitled 'Physics of Active Faults' organized by USGS and NIED, and discussion on the utilization of deep borehole observation for design basis ground motion development was then was deepened at the 2004 OECD/NEED Tsukuba WS. In addition to this study history, a series of WSs on Seismic Observation in Deep Boreholes and its Application organized by OECD, IAEA and JNES was planned. The author also explained that at the first SODB WS, he expected deep borehole observation to be used to observe the activity of specific faults with high accuracy, to detect the detailed structure of those specific faults, and to estimate the asperity distribution in order to establish a practical approach to design basis earthquakes for nuclear power plant design. Recently, however, he has come to think that SODB will help find hidden faults and help observe the conditions of old faults. He also mentioned that he believes that in the future SODB can be used for re-activity evaluation of tertiary faults and evaluation of the movement of local fracture zones