and I'm in northern Virginia near DC and a huge chunk of my Internet traffic goes to the Ashburn area, which is about 30 miles to the west of me. there are massive data centers all over the world, almost never at the premises of the Internet companies themselves.

you seem to have a fundamental misunderstanding of the Internet, my friend.

California is a big place and Silicon Valley occupies a very small portion of it. Today's earthquake has had very little, if any, effect here; so that's not the reason your traffic is being rerouted. I didn't even feel the quake, trains are still running, it's life as normal unless you live in Napa Valley (north of Silicon Valley).