The tsunameter and real-time tsunami forecasting
Bernard, E.N., F.I. González, and V.V. Titov
Chikyu Monthly, 27(3), (in Japanese), 210215 (2005)
The tsunameter is an instrument that measures the amplitude over time of tsunamis in the deep ocean. Just as seismometers have been essential to progress in the field of earthquake research, a tsunameter is critical to the further advancement of tsunami research and hazard mitigation. The U.S. National Tsunami Hazard Mitigation Program (NTHMP), led by the National Oceanic and Atmospheric Administration (NOAA), has developed and field-tested the first generation of reliable portable tsunameters (Figure 1) and successfully established a Pacific network (Bernard et al., 2001; González et al., 2004). The operational network is a powerful catalyst for the revolutionary paradigm shift now underway in tsunami research and forecasting—away from indirect observations and toward direct, high-quality measurements and analyses of the tsunami itself.
Until now, tsunami research and operational decisions of NOAA’s Pacific Tsunami Warning Center (PTWC) and West Coast and Alaska Warning Center (WCATWC) have depended primarily on analyses of seismic information and coastal tide gage measurements. Though valuable, these data are essentially indirect and their interpretation is difficult. Seismic data interpretation involves poorly understood seismic/hydrodynamic coupling. Similarly, the interpretation of tide gage data is difficult because of the complex tsunami transformations induced by interaction with continental shelf, coastline, and harbor features. Furthermore, a tide gage may not survive the impact of the tsunami itself and, if it does survive, the data are not reported until after the tsunami strikes a coastal community. Finally, though coastal tide gages are very useful in detecting tsunamis (and extremely valuable in post-event scientific case studies) they cannot provide direct, deep ocean measurements of tsunamis as they propagate from the source to coastal communities. Tsunameter data are essential to forecast tsunamis.
Engineering advances at NOAA’s Pacific Marine Environmental Laboratory (PMEL) have led to a highly reliable system that acquires and delivers direct tsunami measurements from deep ocean locations between the tsunami generating event and distant communities, and transmits these data in real time to tsunami warning centers and the Internet.