Telltale tsunami sounds could buy more warning time (By RyanFMandelbaum)
Editor’s Note : On January 15 the eruption of a volcano near Tonga triggered a far-ranging tsunami. This story about detecting tsunamis created by earthquakes is being republished in light of this event.
Buoys operate as today's state-of-the-art tsunami-detection system. Seismic data can tell officials that an underwater earthquake has occurred, but strategically placed floating sensors often give the key warning if the earthquake has created a potentially devastating series of waves. Even so, warnings are often issued only minutes before a tsunami hits—if at all.
Usama Kadri, an applied mathematician and engineer at Cardiff University in Wales and the Massachusetts Institute of Technology, is one these researchers. He is especially interested in the “acoustic gravity waves” that tsunami-generating earthquakes produce. These underwater sound waves have such low frequencies that gravitational forces can alter their wavelength and speed under a sudden change in pressure.
As outlined in the Journal of Geophysical Research, Kadri ran a simulation with data from the December 2004 Indian Ocean tsunami, which killed hundreds of thousands of people. It took two hours for those waves to hit Sri Lanka, for example, but the island nation received no tsunami warning.
Kadri's work is important but still theoretical—and contains simplified assumptions, says Ali Abdolali, a postdoctoral researcher at the University of Delaware's Center for Applied Coastal Research. Abdolali is also trying to decipher the underwater sound waves that emanate from a tsunami-causing quake.