The 6.4-magnitude temblor in southern Guerrero state had an epicenter about 9 miles (15 kilometers) north of Tecpan de Galeana and about 171 miles (277 kilometers) southwest of Mexico City, according to the U.S. Geological Survey. There were no immediate reports of injuries or damage.
The quake had a depth of 15 miles (23 kilometers). There was only mild shaking in the resort city of Acapulco, according to an Associated Press reporter there. The USGS downgraded the magnitude from 6.8.
Carmen Lopez, an elegantly dressed businesswoman from Michoacan, was leaving a downtown Mexico City office building when the ground began to sway. She dashed across the street to a leafy median as light poles swayed violently above her.
"That was just too scary," said Lopez, as she quickly started dialing her cellphone to alert friends and family.
Behind her, thousands of people poured out from neighboring office buildings, following pre-planned evacuation routes to areas considered safe from any potential of falling glass.
Mexico City is vulnerable to distant earthquakes because much of it sits atop the muddy sediments of drained lake beds. They jiggle like jelly when the quake waves hit.
A 7.2-magnitude quake with an epicenter about 40 miles (66 kilometers) from Thursday's quake shook central and southern Mexico on April 18.
A magnitude-8.1 quake that killed at least 6,000 people and destroyed many buildings in Mexico City in 1985 was centered 250 miles (400 kilometers) away on the Pacific Coast.