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Laser reveals hidden earthquake “time bombs”

Nov. 8, 2006
Courtesy University of Leicester
and World Science staff

Us­ing a la­ser mount­ed on an air­craft, sci­en­tists say they’ve found earth­quake-prone fault lines pre­vi­ous­ly hid­den by for­est—“time bombs” whose dan­ger can on­ly now be rec­og­nized and stud­ied.

Courtesy University of Leicester


A fault is a crack in the Earth’s crust ac­com­pa­nied by a shift in the ground on either side. Sud­den move­ments like this can pro­duce earth­quakes.

“Lo­cat­ing earth­quake-prone faults in fo­r­ested moun­tain­ous re­gions
… has al­ways been a prob­lem to geo­sci­en­t­ists,” said Dick­son Cun­ning­ham of the Uni­ver­si­ty of Lei­ces­ter, U.K., one of the re­search­ers.

A 2005 earth­quake in the Kash­mir re­gion of Pa­ki­stan, he added, was an ex­am­ple of the hor­ri­fy­ing sur­p­ri­ses these con­cealed faults can spring.

“Many re­gions of the world have un­dis­cov­ered seis­mi­c­al­ly ac­t­ive faults hid­den by dense for­ests,” in­clud­ing In­do­ne­sia, In­dia, north­west­ern North Amer­i­ca, all An­de­an na­tions and Eu­rope’s al­pine coun­tries, Cun­ning­ham said.

A team of ge­ol­o­gists and ge­ogra­phers from the uni­ver­si­ty said the la­ser tech­nique—called Li­DAR, for light de­tec­tion and rang­ing—“vir­tu­al­ly de­for­ests” the land­s­cape to re­veal these de­tails. 

Us­ing it, they said, they mapped re­cent­ly ac­t­ive, earth­quake-prone faults in the south­east­ern Alps in Slo­ve­nia. The re­sults ap­pear in the cur­rent is­sue of the jour­nal Ge­o­phys­i­cal Re­search Let­ters. The top­o­graph­ic im­ages of two ma­jor Slo­ve­ni­an faults, known as the Idrija and Ravne strike-slip faults, shed light on both sys­tems’ struc­ture and his­to­ry, the study found.

“For the first time, we are able to see how the faults con­nect at the sur­face and cut the land­scape. This al­lows us to as­sess wheth­er the faults are like­ly to pro­duce large earth­quakes or small events,” he said, and pro­vides a frame­work for more de­tailed anal­y­ses to help pre­dict the next big quake.

A ex­cur­sion on-site last Au­gust ver­i­fied the sky ob­ser­va­tions, the uni­ver­si­ty’s Kev­in Tan­sey said. “As we trekked through the for­est we found over­whelm­ing ev­i­dence for pre­vi­ous fault ac­tiv­i­ty, nev­er be­fore seen by earth sci­en­tists. We are now build­ing on our in­i­tial re­sults with fol­low­up re­search.”


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Using a laser mounted on an aircraft, scientists say they’ve revealed earthquake fault lines that until now were hidden by forest—ticking time bombs whose danger can only now be recognized and studied. “Locating earthquake-prone faults in forested mountainous regions and understanding the potential seismic hazard they pose… has always been a problem to geoscientists,” said Dickson Cunningham of the University of Leicester, U.K., one of the researchers. A 2005 earthquake in the Kashmir region of Pakistan and India, he added, was a terrifying example of how hidden faults can pose serious and unrecognized hazards. A team of geologists and geographers from the university said their laser technique—called LiDAR, for light detection and ranging—”virtually deforests” the landscape to reveal these details. Using it, they mapped recently active, earthquake-prone faults in the southeastern Alps in Slovenia. Their results appear in the current issue of the journal Geophysical Research Letters. “Many regions of the world have undiscovered seismically active faults hidden by dense forests,” including Indonesia, India, northwestern North America, all Andean nations and Europ’e’s alpine countries, Cunningham said. The topographic images of two major Slovenian plate boundary faults, known as the Idrija and Ravne strike-slip faults, shed light on both systems’ structure and history, the study found. “For the first time, we are able to see how the faults connect at the surface and cut the landscape. This allows us to assess whether the faults are likely to produce large earthquakes or small events,” he said, and provides a framework for more detailed analyses to help predict the next big quake. A excursion on-site last August verified the sky observations, the university’s Kevin Tansey said. “As we trekked through the forest we found overwhelming evidence for previous fault activity, never before seen by earth scientists. We are now building on our initial results with follow-up research.”