From hata at gsi.go.jp Thu May 19 19:04:18 2011 From: hata at gsi.go.jp (Yuki Hatanaka) Date: Fri, 20 May 2011 11:04:18 +0900 Subject: [IGSMAIL-6404] short note on status of GEONET soon after the M9.0 Earthquake, Japan Message-ID: <4DD5CC22.8040906@gsi.go.jp> Dear colleagues, Recently I get an inquiry to share information of our experience of troubles occurred on GEONET (the dense GPS observation network and system in Japan) during and after response to the 2011 off the Pacific Coast of Tohoku, Japan Earthquake (March 11, 2011, M9.0). I would like to copy the short note below since there may be IGS members who are interested in the information: - 3 sites were heavily damaged by the earthquake and tsunami. - The electricity was down in Tohoku area soon after the event. The power was supplied by backup batteries for several hours to ~72 hour depending on sites. Within 72 hours, the observation was stopped at about 40 sites because the batteries were out and the electricity was not restored. Number of stopped sites had decreased as the recovery of electricity progressed. GSI has been setting solar power for 5 sites. - There are two communication means to GEONET sites, IP-VPN and cell phone. The realtime data transfer by IP-VPN connection had been working for a while after the first event. IP-VPN connection to 358 sites in northern area of Japan was cut about 30 minutes after the first event (probably due to the Tsunami). The IP-VPN connection to about 100 sites was recovered within a few hours. Cell phone line are used to retrieve the data (not in realtime) from the remaining sites. The cell phone line was also damaged for two sites. (One is Oshika site where the largest displacement is observed.) The data of those sites are collected when GSI's staffs visited them a week after the event. - The routine analysis system worked without trouble. However, the movement of the fiducial sites (TSUKUBA) is so large (~60cm) that not only the translation errors but also scale and rotation errors of a few tens of ppb were expected for the quick solutions (Q3; every 3 hours with 6 hours data window) and the rapid solutions (R3; every 24hours) for which the nominal coordinates were applied. Initially, we used these results without correction to get the rough estimate of fault parameters. The routine solutions and fault parameters were re-analyzed a few days later by taking the movement of the fiducial site into account. (The final solutions (F3) are almost free from such errors since the coordinates of fiducial site given by analysis with IGS stations in surrounding Asian region.) ---------------------------------------------------- Yuki Hatanaka, Ph.D, Geospatial Information Authority of Japan (GSI) e-mail : hata at gsi.go.jp ----------------------------------------------------