HR: 0800h
AN: G51B-0824    [Abstracts]
TI: Undersea intraplate crustal movement off Miyagi Prefecture, NE Japan
AU: * Fujita, M
EM: masayuki-fujita@kaiho.mlit.go.jp
AF: Hydrographic and Oceanographic Department, Japan Coast Guard, 5-3-1 Tsukiji, Chuo-ku, Tokyo, 104-0045 Japan
AU: Ishikawa, T
EM: tadashi-ishikawa@kaiho.mlit.go.jp
AF: Hydrographic and Oceanographic Department, Japan Coast Guard, 5-3-1 Tsukiji, Chuo-ku, Tokyo, 104-0045 Japan
AU: Matsumoto, Y
EM: yoshihiro-matsumoto@kaiho.mlit.go.jp
AF: Hydrographic and Oceanographic Department, Japan Coast Guard, 5-3-1 Tsukiji, Chuo-ku, Tokyo, 104-0045 Japan
AU: Mochizuki, M
EM: moma@iis.u-tokyo.ac.jp
AF: Institute of Industrial Science, Univ. of Tokyo, 4-6-1 Komaba, Meguro-ku, Tokyo, 153-8505 Japan
AU: Sato, M
EM: mariko-sato@kaiho.mlit.go.jp
AF: Hydrographic and Oceanographic Department, Japan Coast Guard, 5-3-1 Tsukiji, Chuo-ku, Tokyo, 104-0045 Japan
AU: Yabuki, T
EM: tetsuichirou-yabuki@kaiho.mlit.go.jp
AF: Hydrographic and Oceanographic Department, Japan Coast Guard, 5-3-1 Tsukiji, Chuo-ku, Tokyo, 104-0045 Japan
AU: Asada, A
EM: asada@iis.u-tokyo.ac.jp
AF: Institute of Industrial Science, Univ. of Tokyo, 4-6-1 Komaba, Meguro-ku, Tokyo, 153-8505 Japan
AU: Colombo, O L
EM: ocolombo@bowie.gsfc.nasa.gov
AF: G.E.S.T./NASA Goddard Space Flight Center, Code 926, Greenbelt, MD 20771 United States
AB: We have been measuring undersea crustal movement, using the GPS/Acoustic combination technique, at the Off-Miyagi seafloor reference point (MYGI), located about 100km landward from the axis of the Japan Trench, NE Japan, where huge interplate earthquakes have repeated with a relatively regular interval of about 30 to 40 years. The primary purpose of our observation is to detect and monitor the intraplate deformation caused by the subduction of the Pacific plate. A linear inversion method is adopted to determine the position of seafloor stations from coordinates of moving survey vessel determined by the kinematic GPS technique and measured travel times of acoustic waves in the seawater. The positioning accuracy is substantially improved by estimating the temporal variation of the acoustic velocity structure. A time series of horizontal coordinates of MYGI, obtained from seven campaign observations for the period 2002-2005, exhibits a linear trend with a scattering rms of about 2-3cm. A linear fit to the time series gives an intraplate crustal velocity of more than several centimeters per year towards the WNW, which implies strong interplate coupling around this region. The precision of each campaign solution was examined at MYGI through comparison of independent oneday subset solutions within the campaign. Similar comparisons were also made for positioning results at some reference points, other than MYGI, that we have installed around Japan. The resultant repeatability looks to be well correlated with the temporal and spatial stability of the acoustic velocity structure in the seawater, depending on the region as well as the season.
DE: 1209 Tectonic deformation (6924)
DE: 1294 Instruments and techniques
SC: Geodesy [G]
MN: Fall Meeting 2005