March 11, 2011 By Matt Williams
The 20-foot-high tsunami that slammed ashore in northern Japan on Friday, March 11, has taken an untold number of lives and caused incalculable damage as homes, cars and ships were inundated by the sea.
The water displaced by the magnitude 8.9 temblor, the fifth most powerful earthquake in the world since 1900, propagated outward across the entire Pacific. The surge arrived hours later and caused localized damage on the shorelines of Hawaii, Washington, Oregon and California.
The worldwide event evoked memories of the 2004 Indian Ocean tsunami, which killed 250,000 near the coastline as the monstrous waves hit. The disaster highlighted the need for better tsunami data and an early warning system for coastal areas. The National Oceanic and Atmospheric Administration took the lead.
By 2008 the agency had placed 32 sensor buoys in the Pacific. The so-called “DART” buoys include a tsunometer on the ocean floor that measures wave height and water pressure at 15-second intervals and then predicts what the wave height will be in the next interval. The sensor on the ocean floor then sends the measurement to the buoy on the surface via an acoustic modem. If the difference between the actual measurement and the predicted measurement exceeds a certain threshold, then the buoy sends a report of the deviation to a tsunami warning center via satellite link.
This wealth of data allowed scientists to estimate the intensity, wave height and projected time of landfall for the tsunami that struck Japan and then came ashore on the rest of the Pacific Rim. This lead time gave local authorities around the world the ability to close beaches and evacuate low-lying areas in advance.
Read about how this buoy technology has improved during the last 20 years in a story featured in Emergency Management magazine, a sister publication of Government Technology.
The tsunami was the aftermath of the initial quake, which gashed and displaced a 150-mile-long and 50-mile-wide area of the ocean’s crust, according to the U.S. Geological Survey.
Hundreds of miles away, many people working in Toyko skyscrapers knew the earthquake was coming. Japan has invested millions of dollars in an earthquake warning system that detects the waves that are given off by earthquakes. The first one, called the primary wave (P wave), is detected by sensors. Once detected, the wave is immediately registered on computers that determine its size and broadcast warnings via TV and cell phones. The system also automatically shut down energy and industrial facilities, and transportation services.
The system gives an estimated intensity and arrival time of the “S” wave, which causes the most damage. The estimates are made on analysis of wave form data observed by seismographs near the earthquake’s epicenter.
The earthquake took 8.6 seconds from the point that it registered on the system, to the time the warning was given, according to Peggy Hellweg, a seismologist at the University of California, Berkeley.
Japan isn’t the only country working on the technology that enables an early warning system for earthquakes. California researchers are attempting to secure the estimated $80 million necessary to install enough sensors across the length of the state’s seismically active faults, according to another story in Emergency Management magazine. The researchers hope to have an early warning system prototype as soon as 2013.
Read the story, Earthquake Early Warning System Coming to California.
Another effort based at Stanford University in California, called the Quake-Catcher Network, is bringing together data from USB motion sensors attached to personal computers — about 1,300 of them were in place worldwide as of last year. Researchers said the real-time data could be the foundation to form a worldwide early warning system.
Read the story, Computers Map, Track Earthquakes Using Motion Sensors.
Government Technology Web Writer Brian Heaton and editorial staff contributed to this report.
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