Scientists have known about the faults for years, but now they can actually see them better. Researchers mapped the Tahoe area using technology called LIDAR, where a small aircraft reads the landscape using laser points.
Before that, they had to use boots on the ground, says Jim Howle of the USGS.
HOWLE: "But it was very hard to trace exactly where they went, because the vegetation is so dense."
HOWLE: "The tectonic rates that we have quantified are two to three times greater then previous estimates."