I was visiting Napa Valley over the weekend, and at around 3:30AM on Sunday morning I awoke suddenly to what felt like some giant at the end of the bed shaking it as hard as he could. It was an earthquake. One of the scariest things about an earthquake is that when it happens, you have no idea how serious it is — you only know what it feels like where you are. So of course I turned to Twitter (thank you Twitter!) and the USGS was on the case — it was a 6.1 (later revised to 6.0), with an epicenter about 25 miles away.
It was actually a a relief to find out that the epicenter was so close: I was worried that it might have been closer to San Francisco, which would have meant the shaking we felt was indicitive of a much more catastrophic event. Still, it was hard to go back to sleep after it happened, and of course I wasn't the only one. Jawbone, the makers of the Jawbone UP sleep-tracking device, released this chart showing wearers being woken up by the quake and then slowly going back to sleep. Those closer to the epicenter took longer to recover.
You can read more about the data collection and analysis behind this chart at the Jawbone blog post linked below.
Jawbone blog: How the Napa earthquake affected Bay Area sleepers