An earthquake with a magnitude 7.8 was recorded off Papua New Guinea on Saturday, the U.S. Geological Survey said.
The quake, at a depth of 10 km (6 miles), hit 68 km southwest of Panguna.
The Pacific Tsunami Warning Center said a tsunami warning was in effect for Papua New Guinea and the Solomon Islands.
Yesterday, a 7.2 magnitude earthquake struck southern Mexico's Guerrero state.
The quake's depth at the epicenter was a shallow 15 miles (24 kilometers), the U.S. Geological Survey said.
The Mexican National Seismological Service measured its depth at 6 miles (10 kilometers) and its magnitude as 7.0.
USGS classifies any quake magnitude 7.0 to 7.9 as "major," and any at 8.0 or more as "great."
The earthquake's timing and location could have proved devastating -- it occurred on the Pacific coast between major resort towns of Acapulco and Zihuatanejo during Holy Week, when Mexicans traditionally flock to the beaches, and resorts typically run at full capacity.
Its impact was also felt in Mexico City, 170 miles (273 kilometers) northeast of the epicenter. "I was working in my radio news program ... and we were talking about (author) Gabriel García Marquez's death, when I started to feel how the ground was shaking and the lamps were moving," journalist Sol Rivera said via e-mail.
She urged her listeners to remain calm and to move to a safe space.
Reporters soon called to inform her that everything was OK.
At least one building in the capital was damaged, but there were no reports of major damage, Mexico City Mayor Miguel Angel Mancera toldCNN affiliate FOROtv.
The city's secretary of civil protection, Fausto Lugo, said electricity failed in some areas and that some people reported being trapped inside elevators, but that there were no reports of injuries.
Tecpan is 54 miles (87 kilometers) northwest of Acapulco, where the city's civil protection office said via Twitter that basic services were operating without reports of damage.
Seated on top of three tectonic plates, Mexico is in one of the most seismically active parts of the world. On September 19, 1985, a magnitude-8.1 earthquake killed an estimated 9,500 people in Mexico City.
- Reuters and CNN