Earthquake!

Well, yesterday, a little teensy one, and quite a long way away.  What makes this one interesting is that the seismometer in our house captured it (see below).

USGS says that the earthquake occurred on 2/23 at 04:40:14 UTC.  Our seismometer shows the first burst of primary wave at 04:40:33 – 19 seconds later.  The location of the earthquake (USGS) is 109 kilometers from our house, yielding an average primary wave speed of 5.75 km/s, well within norms for primary waves.  By collecting lots of data like this, for many earthquakes and from many locations, USGS is building up a huge dataset that will let them learn a great deal about the composition of the earth's crust in the areas where they have good coverage (Southern California is one of them)...