Several earthquakes struck within minutes of each other in Oregon, California, and Mexico Wednesday night.
A 6.4 magnitude earthquake shook Mexico City Wednesday evening, just two weeks after a 7.4 magnitude quake damaged hundreds of homes in southern Mexico.
Television pictures showed an office building moving during the tremors, which lasted for two to three minutes, as well as office workers evacuating buildings afterwards.
The epicenter was in Michoacan, a sparsely populated area in the mountains of western Mexico. Authorities said no major damage had been reported.
Two other quakes struck off the coast of Oregon and California around the same time.
A quake registering 5.9 struck about 160 miles off the Oregon coast about 3:40 p.m. local time on Wednesday. There were no immediate reports of damage. And residents near the Gulf of California were shaken by a 5.3 magnitude quake near Mendocino, Calif.
The West Coast and Alaska Tsunami Warning Center said no tsunami was expected.
Doug Gibbons of the U.S. Geological Survey said there there is no evidence that the quakes were related to two massive earthquakes that struck Indonesia on Wednesday.
He cautioned not to look too deeply into the series of quakes, adding that they are in different parts of the world, produced by unrelated tectonic plates.
Analysts said it will take months if not years to determine if they are related.
Meanwhile, Indonesians feel especially blessed after escaping Wednesdays' quakes.
Residents surveying damage from the powerful earthquakes that reignited memories of the devastating 2004 Indian Ocean tsunami said Thursday they could hardly believe their luck.
Five people died from heart attacks, and a few others were injured as mobs used cars and motorcycles to flee to high ground in Indonesia's westernmost province of Aceh - closest to the epicenters.