While at work late, I felt a pretty good jolt, which marked the arrival of yet another of California’s exciting pastimes: the regular Hayward fault earthquake. Displacement seemed mostly vertical, fairly obvious, but lasted only a few seconds. Once you are fairly sure that the earthquake is not bad at your location, you immediately wonder “is the rest of the Bay Area in ruin?” A quick trip to the USGS real time earthquake map for California assured us that the earthquake was a reasonably small 3.9 earthquake centered a couple of kilometers from our location. The USGS has a automatically generated page to describe the event. Whew! Guess the house will still be standing when I get home tonight.

On the right you can see traces of the earthquake activity. You can see that activity continues for up to a minute after the initial quake. They run these detectors at high gains so the display is significantly clipped.
Neat.