Lake Tahoe on shaky ground
February 17, 2003
INCLINE VILLAGE — The fault lines in Lake Tahoe create earthquakes strong enough to generate a tsunami every 3,000 to 4,500 years.
Data collected by the Scripps Institute of Oceanography indicate the faults are moving 0.4 to 0.6 millimeters each year. The institute, however, is still working to determine when the last major seismic event occurred.
“That’s something we’re trying figure out,” said Graham Kent, of the Scripps Institute of Oceanography, during a scientific forum Friday organized by the Lake Tahoe Environmental Education Coalition. “(We do know) the Lake Tahoe Basin has very active faults in it and they are ongoing.”
Scientists began studying the geological history of Lake Tahoe more closely after the U.S. Geological Survey published a detailed map of it in 1998.
Kent and other scientists from the institute have spent two or three weeks each summer since 1999 making three-dimensional maps of the lake by using sound waves.
Three active fault lines exist in Lake Tahoe and there could be a fourth, but it is probably not an active one, Kent said.
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The faults exist on the north side of the lake. The one farthest west runs north of Emerald Bay to Dollar Point. A second fault runs through Crystal Bay. The third fault heads northeast through Incline Village over Mt. Rose.
The faults are what led to the creation of Lake Tahoe about 3 million years ago. They make the lake drop to the east, which is why the deepest parts of the lake are near Incline Village, Kent said.
Data indicate Incline Village will sink 15 meters in 10,000 to 20,000 years.
“So that means if you’re sitting on the beach at Incline, the water would be 50 feet over your head,” Kent said.
When scientists study the lake they look for reference points. One reference point is McKinney Bay at Homewood. A landslide created the bay about 50,000 years ago — probably the result of an earthquake.
Future examination of Lake Tahoe will involve the use of remote-operated vehicles, core sampling and trench digging near fault lines, Kent said.
The level of Lake Tahoe was also discussed at the forum. Craig Morgan, an engineer based at South Shore, pointed out that geological evidence around the basin shows the lake at various points in time was 100 to 700 feet higher than it is today.
Water formed indentations at places such as Eagle Rock, which is near Tahoe Pines, and at Cave Rock. Both locations sit at about 6,500 feet, whereas the natural rim of Lake Tahoe today is 6,225 feet.
— Gregory Crofton can be reached at (530) 542-8045 or by e-mail at email@example.com