Magnitude 8.2 Earthquake Strikes Mexico; Tsunami Alert Issued For 8 Coastal Nations 

An earthquake of a magnitude 8.2 struck off the coast of Chiapas, Mexico, late on Thursday local time, the Pacific Tsunami Warning Center (PTWC) said, citing USGS data.

Tsunami waves have been observed, it said.

Tsunami waves of more than 3 meters, or nearly 10 feet, above the tide level are possible along some coasts of Mexico, the PTWC said.

It added that tsunami waves of 0.3 to 1 meter above the tide level were possible for some coasts of American Samoa, Antarctica, the Cook Islands, Ecuador, El Salvador, French Polynesia, Guatemala, Kiribati, New Zealand, Samoa, Tokelau, Tuvalu, Vanuatu and Wallis and Futuna.

Tsunami waves of less than 0.3 meters above tide level were possible Colombia, Costa Rica, El Salvador, Hawaii, Honduras, Jarvis Island, Nicaragua, the Northwestern Hawaiian Islands, Palmyra Island, Panama and Peru.

The quake's preliminary reading had been at magnitude 8.0.

The National Weather Service didn't expect a tsunami on the U.S. West Coast or Britich Columbia.

The quake's depth was at 33 kilometers, or 20 miles, the PTWC said.

"It's a big quake. It's about 70 miles offshore, but it's not an unheard of quake," USGS geophysicist Randy Baldwin told NBC News in a phone interview, noting that the mid-American trench has producing a lot of big quakes in the past.

But he added,"This is a large quake. I'm sure that it will be widely felt and possibly damaging."

Reuters reported that people in the capital Mexico City ran into the streets after the quake, adding later that parts of the city were without power.

The quake was the strongest to strike the country since 1985, when a temblor killed thousands, Reuters reported, citing Mexico's civil protection agency.

The European-Mediterranean Seismological Centre (EMSC) said that the quake was also felt in Belize and Guatemala. It estimated that the population in the "felt area" was around 90 million people.