California, US: Scientists at the US Geological Survey (USGS); University of Nevada, Reno; University of California, Berkeley; and the US Army Corps of Engineers; used LiDAR tech to confirm fault zones near Lake Tahoe, California. The study further revealed that these faults could generate earthquakes with magnitudes ranging from 6.3 to 6.9.
“This study is yet one more stunning example of how the availability of LiDAR information to precisely and accurately map the shape of the solid Earth surface beneath vegetation is revolutionizing the geosciences,” said Marcia McNutt, USGS director. “From investigations of geologic hazards to calculations of carbon stored in the forest canopy to simply making the most accurate maps possible, LiDAR returns its investment many times over.”
Linear moraines (boulders, cobbles, gravel and sand deposited by an advancing glacier) were offset by motion on the faults, providing a record of tectonic deformation since the moraines were deposited. The research team created a new 3-D technique to measure the amount of tectonic displacement of moraine crests caused by repeated earthquakes.
The scientists calculated the rates of tectonic displacement by dating the moraines from the last two glaciations in the Tahoe basin, which were around 21,000 and 70,000 years ago.
“Although the Tahoe-Sierra frontal fault zone has long been recognized as forming the tectonic boundary between the Sierra Nevada to the west, and the Basin and Range Province to the east, its level of activity and hence seismic hazard was not fully recognized because dense vegetation obscured the surface expressions of the faults,” said James Howle, a USGS scientist and lead author of the study.
“Using the new LiDAR technology has improved and clarified previous field mapping, has provided visualization of the surface expressions of the faults, and has allowed for accurate measurement of the amount of motion that has occurred on the faults. The results of the study demonstrate that the Tahoe-Sierra frontal fault zone is an important seismic source for the region.”