Real-time observation of tsunami by RTK-GPS

A new tsunami observation system has been developed, which employs the RTK-GPS technique to detect a tsunami before it reaches the coast. The system consists of dual-buoys: the Support-buoy, which is sensitive to wind-waves, and the Sensor-buoy, which is of a spar-type and is insensitive to wind-waves. Both buoys are equipped with a GPS antenna. An experiment using this system was carried out for about nine days in March 1999. Observation data were monitored at the onshore base station. The results showed that hourly averaged data is consistent with ocean tides for both buoys. The Sensor-buoy was found not to respond much to wind-waves compared to the Support-buoy. Thus, it may be preferable to use a spar-type buoy for detecting a tsunami efficiently. Furthermore, a simple frequency analysis showed that a tsunami could be easily separated from higher frequency wind waves if a tsunami is superimposed on regular wind waves.