Usage of Mesh Networking in a Continuous-Global Positioning System Array for Tectonic Monitoring

In recent years, tectonic plate movements have caused huge natural disasters, such as the Great Sumatra-Andaman earthquake and the resulting Asian tsunami, which led to significant loss of human lives and properties (Ammon et al., 2005; Lay et al., 2005). Scientific evidences proved it was the beginning of a new earthquake supper-cycle in this active area (Sieh et al., 2008). In order for scientists to further study such disasters and provide early warning of imminent seismic events, many continuous-Global Positioning System (cGPS) arrays were developed and deployed to monitor the active tectonic plates around the world such as “SuGAr” along the Sumatran fault, “GEONET” covering all Japan islands, and “SCIGN” covering most of southern California. Each of these cGPS arrays contains tens to hundreds of GPS stations. Using precise GPS receivers, antennas and scientific-grade GPS processing software, measurements from each GPS station are able to provide location information with sub-millimeter accuracy. These location data produced by the GPS stations, which are located in the vicinity of active tectonic plates, provided accurate measurements of tectonic movements during the short period of a co-seismic event as well as for the long period observation of post-seismic displacement. The GPS applications in earthquake studies (Segall & Davis, 1997) include monitoring of co-seismic deformation, post seismic and inter-seismic processes. Post seismic (except aftershocks) and inter-seismic deformations are much smaller than co-seismic events, where there is little or no supporting information from seismic measurements. In this instance, GPS can be used to detect the long time inter-seismic strain accumulation which leads to indentify the location of future earthquake (Konca et al., 2008). In cGPS arrays utilizing satellite communications such as the Sumatran cGPS Array (SuGAr), each GPS station in the cGPS array will periodically measure the tectonic and/or meteorological data which will be stored locally. A collection of these observed GPS data will then be sent to a data server through a dedicated satellite link from each station either in real-time or at update intervals ranging from hours to months. At the server, the collected data from the GPS stations will be processed by using closely correlated data from each station to reduce errors in the location measurements. Since the amount of data transmitted from each station could be relatively large, the communication bandwidth and the number of uplinks are the most important factors in terms of operational expenditure. Each satellite