Thursday's temblor was an aftershock, according to the U.S. Geological Survey. It was described as "moderate."
The USGS said the aftershock struck the same area as Tuesday's earthquake, in southern Guerrero state on the Oaxaca border.
Mexico City Mayor Marcelo Ebrard reported there was no major damage. Downtown Mexico City officer workers did evacuate from buildings Thursday.
The USGS says aftershocks may occur after such a large earthquake as Tuesday's 7.4. Aftershocks could be felt days, months or even years after such a big quake, according to the USGS.
Tuesday's earthquake was centered near Ometepec. Experts say that quake was shallow, about 11 miles below the surface. Authorities said the absence of tall buildings in the mountainous rural area is one reason for the lack of casualties.
The Associated Press contributed to this story.