At least it's a pretty darn short distance to run to get 50 feet above the lake if you're on the beach, from what I understand about Tahoe. And since Tahoe is small you'd only have to do so if the quake you feel was strong enough to literally knock you off your feet; any small or moderate quakes you'd feel would be too small to cause a tsunami or would be a quake distant from Tahoe.
Don't have a whole lot of time probably to get 50 feet up, though; probably a couple of minutes, tops.