The U.S. Geological Survey says a magnitude 4.4 earthquake hit the same area on Sunday morning.
The Epicentre is about 18 kilometre west of Calexico. Six other quakes above magnitude 3.0 were also reported within a three-hour period. There have not been any reports of damage or of deaths related to the series of earthquakes.
Increased seismic activity is normal following larger magnitude earthquakes like the one on Easter weekend.
That quake killed 2 people and caused an estimated $100 million in damage to the state of California alone.