From Steve Jones… our earthquake expert…
A small magnitude 2.6 earthquake was registered earlier today at 15:20:10 UTC (9:20:10 am CST) in Alabama, at a location northwest of Birmingham, approximately 129 km (80 mi) from Huntsville. The quake focus was located at a depth of 1 km (0.6 mi) underground. There were no immediate reports of damages in the local area.
In Huntsville, the initial P (pressure) seismic body waves began to arrive some 12 seconds after the quake occurred, and the initial S (shear) body waves were seen at approximately +37 seconds. A phase of surface waves was seen to arrive beginning about 46 seconds after the quake, peaking at +51 seconds with a maximum vertical ground movement of approximately 144 micrometers (um) measured at the AlabamaQuake seismic station.
The local seismogram and earthquake epicenter location map have been posted at the AlabamaQuake website (http://alabamaquake.com) on the “Huntsville Seismograms” and “Recent Earthquake Maps” pages, and have also been attached to this message.