Abstract: The repeated observation of seafloor geodetic network can be used to study the seafloor plate technic and the process of marine disaster such as seafloor earthquake. However, affected by observation condition, power supply and other factors, it is hard to achieve continuous observation for a long time. To solve the displacement compensation and site offset calculation problems in the replacement of old and new underwater geodetic stations in time series observations, the center point method can be used to calculate the displacement relative to the virtual center point coordinates of the underwater geodetic station network, and then construct the underwater geodetic coordinate the series to monitor underwater tectonic movement. For the same problem. Referring to the maintenance way of the terrestrial reference frame, we directly use the time series observation data of the seafloor geodetic network that may have discontinuities, and propose a multi station joint processing model of the seafloor geodetic coordinates based on the reference protocol epoch, in other words, in a regional geodetic network the coordinates of each station are treated as local parameters, and the velocity is used as a common parameter. The new proposed method is not only suitable for the geodetic dynamic reference frame maintenance, but also can be conducive to the implementation of fine quality control of the coordinate time series of each geodetic station in the regional network. The experimental results show that, the difference of annual velocity estimation difference of seafloor geodetic network between the two methods is about 3 mm/a. The new proposed method is a substitute for the center point method, and the robust estimation results are more reliable. This study provides a way for maintaining the national seafloor space benchmark.

Key words: seafloor geodesy, plate movement, station velocity, robust estimation, disaster monitoring