Geology: "Are Tsunamis Predictable?"
"Are Tsunamis Predictable?"by Josh Clark
"By all rights, the 8.8-magnitude earthquake that struck Chile in February 2010 should've caused a tsunami that wreaked havoc on Hawaii. The quake was massive - tied for the fifth most powerful since 1900. It originated in a subduction zone along the Chile margin, a unique geological area where three tectonic plates are being subsumed by the South American continent. If that wasn't enough of an omen, a 9.5-magnitude quake in Chile 50 years earlier generated a tsunami that bent Hawaiian parking meters like paperclips. Yet, when the 2010 quake occurred, the resulting tsunami arrived in Hawaii with a whimper. In fact, it barely warranted evacuation warnings issued by the National Oceanic and Atmospheric Administration's (NOAA) Pacific Tsunami Warning Center in Hawaii. Those warnings were based on a tsunami model that did not accurately predict the effects of Chilean tsunami. The failure of that model - and the accuracy of another created by NOAA's Center for Tsunami Research in Seattle, Washington - will prove invaluable at predicting future tsunamis. After all, each prediction failure is an opportunity to figure out why the system failed in the first place. But the failure also underscores another question: Are tsunamis predictable?Researchers have become increasingly adept at predicting what a tsunami will look like once it occurs, based on emerging technology and information culled from past quakes and tsunamis. "We're still building models from the 1960 Chilean earthquake," said Chris Goldfinger of Oregon State University. "Twenty years from now, people will be sorting out the models for the 2010 quake. It's really a never-ending process." Models that forecast the effects of tsunamis on Hawaii, for example, must consider an underwater ridge that protects it from most waves.
Forecast models depict the size and number of tsunami waves, approximate arrival time, where the waves will make landfall, and how far inland they will reach. They are compiled by tsunami researchers for faults around the world; like an 8.8-magnitude quake along the Chile margin, for example. When this quake occurred, researchers pulled up models based on this very event; responders based their reactions on the predictions, which led to evacuation warnings. Because of the factors involved in compiling an accurate depiction of a tsunami and the relatively sluggish computing power currently available, researchers compile models before they occur. "It just takes too long to do them in real time," Goldfinger said.
Time is an essential factor following a tsunami, and quickly detecting tsunamis when they occur is as much a part of the field as predicting the course and form they will take. Even a few extra minutes of warning can give people in the tsunami's path time to reach higher ground, which unequivocally saves lives. The Indian Ocean tsunami of 2004 struck land within 20 minutes and killed around a quarter-million people because the area lacked an early warning system. Since around 85 percent of tsunamis come from the Pacific Ocean, American researchers have focused largely on the Pacific Northwest in recent years. Geologists have predicted that the Cascadia subduction zone that runs off the coast from Mendocino, Calif. to Vancouver, British Columbia may be due for a massive quake. It's one of only two fault lines in the U.S. capable of producing a major tsunami.
Since the mid-1990s, NOAA has placed buoys in the Pacific between known faults and land. These buoys are capable of sensing and recording tsunami activity and relay the information back to land as an early warning system. As a tsunami is generated, these tsunameter buoys can provide hours of additional time to reach safety. The profile of a predictable tsunami is still being developed. Most recently, researchers have begun to investigate how to detect faint electrical currents created by tsunamis. As wave action drags ions through saltwater and along the Earth's magnetic field, it generates an electrical field that Manoj Nair of the University of Colorado has proposed may be detected as an early warning system.
Tsunami researchers are taking this science as far as they can, but they consistently run into a roadblock. Most tsunamis are generated by earthquakes, and to predict one before it happens requires the ability to predict a quake. Scientists have thus far been unable to make narrow predictions. "We can't currently predict earthquakes over time scales of days, weeks, months or even a few years," said University of Washington seismologist Heidi Houston. "We have mostly moved to forecasting earthquakes in a region over the next 30 to 50 years." Still, the work tsunami researchers are compiling would prove adequate in predicting tsunamis should earthquakes ever become predictable. "If we could predict an earthquake in sufficient detail, then scientists could do a pretty good job predicting the resulting tsunami," Houston added."
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