Monday's quake struck 27 miles east of Oaxaca at a depth of six miles, the U.S. Geological Survey said. Oaxaca is about 300 miles south of Mexico City. There are no immediate reports of casualties or damage.
The quake triggered emergency alarms and jarred awake residents as far away as Mexico City who scrambled into the streets.
Friday's tremors caused tall buildings in Mexico's capital to sway for over two minutes and revived memories of two earthquakes in September last year that killed several hundred people in Mexico City and other parts of the country.