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Laser technique reveals earthquake trouble spots

08 Nov 2006

Researchers at the University of Leicester, UK, have used a powerful laser mounted on an aircraft to uncover earthquake fault lines hidden by forest cover, which have never before been seen by earth scientists.

The 2005 Kashmir earthquake was a terrifying example of how faults in mountainous regions that pose serious seismic hazards can go unnoticed because they are hidden by forest cover.

Now, however, scientists at the University of Leicester, UK, have shown that airborne LiDAR (light detection and ranging - in this case, a powerful laser mounted on an aircraft) can be used in mountainous terrain to "virtually deforest" the landscape and so reveal details of the forest floor topography, including traces of active faults.

Dickson Cunningham and Kevin Tansey, supported by Masters student Stephen Grebby, have already used the technique to map the distribution of recently active earthquake-prone faults in the southeastern Alps in Slovenia.

Topographic images derived from LiDAR data of two major plate boundary faults, the Idrija and Ravne strike-slip faults in Slovenia, reveal geomorphological and structural features that shed light on the overall architecture and movement history of both fault systems. Their key research results have been published in the latest issue of Geophysical Research Letters.

"For the first time, we are able to see how the faults connect at the surface and cut the landscape," said Cunningham. "This allows us to assess whether the faults are likely to produce large earthquakes or small events in the future."

The images also enable earth scientists to identify suitable sites for detailed fault analysis. Such studies can help to determine how often major earthquakes are likely to happen, and also provide a probabilistic estimate of the timing and magnitude of the next major earthquake.

A field excursion in August 2006 verified the remote observations. "As we trekked through the forest we found overwhelming evidence for previous fault activity, never before seen by earth scientists," said Tansey. "We are now building on our initial results with follow-up research and have established the UK's first interdisciplinary LiDAR research unit here at Leicester with support from the Ordnance Survey and the British Geological Survey."

According to Cunningham, locating earthquake-prone faults in forested mountainous regions and understanding the potential seismic hazard they pose to local population centers has always been a problem for geoscientists. "Many regions of the world have undiscovered seismically active faults hidden by dense forests, including Indonesia, India, north west North America, all Andean nations and the alpine countries of Europe," he said.

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