An M3.1 earthquake was recorded in central Arizona last night about 11:07 pm between Phoenix and Prescott, about 10 miles north of Black Canyon City.
Ramon Arrowsmith at ASU posted the initial report on this. He's asked for anyone who felt this quake to let him know. Ramon comments that earthquakes are rare in this region and there are no mapped faults in the area.
[right, location map with historical seismicity. Credit, Ramon Arrowsmith, ASU]
The seismogram above is from station X16A near Pine, AZ. The M3.1 event can be seen just right of the 6:00 time marker (about 6:07 GMT)