The Arizona Geological Survey said two quakes occurred, including a magnitude 2.6 quake at 12:07 a.m.
There has been a swarm of 21 quakes in an area along the Arizona-Nevada line south-southwest of Littlefield, AZ, which is also close to southwestern Utah and the frequency and span puzzles geologists.
The survey said the area has several active faults and that its geologic features suggest there could be additional potentially active faults just north of the largest quake.
The largest in the swarm was a magnitude 3.4 quake was reported at 2:23 a.m. on April 8. SOURCE