The earthquake was caused by the North American Plate sliding past the Caribbean Plate at a conservative plate margin. Both plates move in the same direction, but one moves faster than the other. The pressure that was built up because of the friction between the 2 plates was eventually released causing a magnitude 7 earthquake on the Richter Scale with an epicentre 16 miles West of Port-au-Prince and a shallow focus of 5 miles. The earthquake struck at 16:53 (4:53 pm) local time on Tuesday 12 January 2010.