OREGON STATE UNIVERSITY

LIDAR mapping after Samoan tsunami could boost research efforts

11/04/2009

 

CORVALLIS, Ore. – The use of sophisticated LIDAR imaging following the recent earthquake and tsunami in Samoa should give scientists some of the most accurate and detailed maps ever made of the forces of these powerful events, helping them to improve building design and other mitigation efforts.

In this initiative, researchers from Oregon State University worked with the geoengineering extreme events reconnaissance team sponsored by the National Science Foundation and led by Jennifer Donahue of Geosyntec, Inc. They went to American Samoa immediately after the event and were able to capture LIDAR images for one of the first times following a tsunami.

 “LIDAR is a recent technology, and with it we can produce images and maps that are accurate to within a few millimeters,” said Michael Olsen, an assistant professor of geomatics with the OSU School of Civil and Construction Engineering. “By arriving at the disaster site quickly, we were able to make maps before things got cleaned up or vegetation grew back. This will provide excellent data for research on tsunami wave forces, impacts on buildings, response of structures and other issues.”

LIDAR, which stands for light detection and ranging, is a technology that can rapidly map topography, structures and other objects with precise detail. It has been used, for instance, in aerial applications to spot ancient earthquake ruptures or landslides, and to map ground deformation from recent earthquakes. In Samoa, it was used on the ground to provide highly detailed, three-dimensional models of tsunami damage such as ground scouring, sediment transport, high water marks, building damage and many other features.

The destruction in Samoa was caused mostly by tsunami impacts rather than the ground shaking from the earthquake, Olsen said. Wave heights varied greatly from about six to almost 40 feet high, causing enormous devastation in some villages.

The permanent record provided by the Samoan LIDAR data, Olsen said, will help scientists reconstruct exactly how the tsunami hit, and to determine what types of buildings, foundation designs, structural placement or other features were best able to resist its forces.

The research program there was aided by equipment and software loaned by David Evans and Associates, Inc., in Portland, Ore., and Leica Geosystems in San Ramon, Calif. A strategic partnership was recently established between these organizations to provide students with advanced training in geomatics.

OSU experts and others will use this information for tsunami modeling, advance planning and mitigation programs. The university has several earthquake and tsunami experts, and operates the world’s most sophisticated “tsunami wave basin” designed to simulate these events and test their effects on various structures or landforms. Solomon Yim, a professor of civil engineering, is leading another expedition in American Samoa to study structural damage.

OSU is also assisting community leaders in Cannon Beach, Ore., who are considering the construction of the nation’s first structure designed specifically to resist the forces of a tsunami and serve as a refuge that people might quickly move to for protection. The Cascadia Subduction Zone off the Pacific Northwest is believed to have caused numerous earthquakes and tsunamis in the past, the last one in the year 1700, and experts say it’s inevitable that more such events will occur in the future.

Although far less destructive than the massive earthquake and tsunami that hit East Asia in 2004, the Samoan event caused considerable damage and is believed to have killed more than 175 people. It was triggered by a magnitude 8.0 earthquake deep beneath the sea near Samoa.

“Where the worst of the tsunami hit on American Samoa, there was just complete destruction, total ruin,” Olsen said.