Real-time tsunami analysis
Most tsunamis are produced by tectonic movement of the ocean-floor, resulting from mega-thrust earthquakes. Reviewing the historical earthquakes followed by tsunamis along the Nankai trough, SW Japan, a large tsunami will be also produced by the next Tonankai mega-thrust earthquake, which will be a threat to the coastal area of SW Japan. DONET consists of several tens of tsunami sensors (high precision pressure sensors) in addition to the seismic sensors in the Tonankai earthquake source area, which possibly detect tsunami earlier than their arrivals at the coastal areas. One of our goals is to contribute to mitigate tsunami related disasters by providing the tsunami alert. To achieve our goals, we are now developing a new technique to predict tsunami height and arrival time immediately after the earthquake by using real-time information from DONET.
DONET recorded distinct tsunami signals of the 2011 Tohoku earthquake with pressure gauges. The maximum amplitude at the stations is about 0.2-0.3 m in the period band between 100 to 10000 sec. These signals were found 15 min before the arrivals at the nearest site, Owase city, Mie prefecture. This shows that the offshore DONET data are very useful to quickly estimate water heights in near shore areas for disaster mitigation. The pressure gauge data are also useful for analyzing micro-tsunami, geodetic deformation, tide, water temperature, and related ocean phenomena.