Just a little earthquake

Dinner was interrupted by a very brief, loud banging and rattling 3.9 earthquake whose source was 3 kilometers away and 12 km down. It felt like a thunderclap from below, here and gone in a few seconds. What did your About Geology Guide—wise, aware, experienced—do?

I jumped to my feet, stood there and yelled "Earthquake!" of course. A chair fell, but only because the cat knocked it over running away from me. But after a few minutes, I collected my wits and remembered the Web-based shaking map site used by the U.S. Geological Survey, and added my report to several thousand already entered by Bay area citizens. You ought to too, says the USGS: "Even if you did not feel the earthquake, your questionnaire is important: in areas of lighter shaking, the "not-felt" responses are needed to prevent the average ZIP-code intensities from being too high."