Monitoring seafloor crustal movements: progress report of relative positioning on the seafloor

A progress report on underwater systems being developed for monitoring seafloor crustal movements is presented. The horizontal relative positioning utilizes precise acoustic ranging with linear pulse compression techniques. We estimate that temperature effects on horizontal ranging on the deep seafloor can be corrected with cm-oder accuracy. We also examine ocean bottom pressure gauges and an ocean bottom gravimeter for monitoring the vertical crustal movement. Both have a resolution of a few centimetres, but further studies are needed to ensure the long-term stability.