As you may know northern California had a 6.5 Earthquake yesterday. It took place about 200 miles north of me so I didn't feel it though an hour before I did feel a 2.1 that took place about 60 miles south of me. On Thursday there was a 4.1 near the same location but I was driving and didn't feel it. It was a slight jolt but you know it is a quake. It's worth noting that we are coming up on a solar eclipse on the 15th. Those often trigger earthquakes and maybe the gravitational pressure is building up for some before the eclipse. Quakes can be hard to predict because the theory is they occur when a fault that has been effected by the increased gravitational effect (even of new and full moons) settles. Unless we have a way of seeing these faults it would be difficult to know where they might occur.
Track US quakes here: http://earthquake.usgs.gov/earthquakes/recenteqsus/
