Strong earthquake strikes off Mexican coast

A STRONG earthquake struck off the coast of Mexico today, waking up people living near the Gulf of California only hours after a separate quake swayed tall buildings in Mexico City, causing evacuations.

Authorities said neither quake caused major damage or injuries. The tremor late on Wednesday afternoon was the third strong one to shake Mexico City in as many weeks and rattled the nerves of weary residents.

The US Geological Survey said Thursday's 6.9-magnitude quake hit the waters between the Baja peninsula and the northern state of Sonora at 12.15am local time.

People in the city of Hermosillo woke up as their beds swayed and their ceiling fans shook.

Luis Enrique Cordova, director of emergency services in Sonora, said confused residents clogged the phone lines of the civil protection office in Hermosillo, capital of the state and home to some 700,000. But Mr Cordova said no major damage had been detected in the region.

"I was on my bed, leaning against the wall, and the fans kept moving non-stop, side to side," said Carlos Morales, a teacher in Hermosillo.

The quake was centered 133 kilometres northeast of Guerrero Negro and 215km west of Hermosillo. It hit about 10.3km below the surface.

Hours earlier, a 6.4-magnitude quake struck a sparsely populated area in the mountains of western Michoacan state and caused multi-story buildings to sway more than 322km away in Mexico City.

A 7.4-magnitude earthquake on March 20 was felt strongly in the nation's capital. It damaged hundreds of homes and killed at least two people near the border between Guerrero and Oaxaca states.

Mexico's seismological service said that quake has been followed by close to 400 aftershocks, including one of magnitude 6.0 that also rocked the capital.

Shortly after Wednesday's quake, social networks began buzzing with comments of scared residents.

"We just had another earthquake, this is damn scary," wrote a Twitter user.

A quake alert application for Blackberrys that Mexico City's Government touted last week did not work on Wednesday.

Mexico City Mayor Marcelo Ebrard said the alert system so far is set up only for quakes centred in the southern states of Guerrero and Oaxaca. He said it will begin to work for any tremors in Michoacan in the next few days.

Scientists said the quakes shaking Mexico have not been triggered by each other and are the result of having three tectonic plates come together off Mexico's Pacific coast.

Don Blakeman, geophysicist with the US Geological Survey, said quakes that hit in different locations are not related and it's simply coincidence that they happen so close together.

"Mexico, Japan, Indonesia and California are seismic reactive areas and they are always going to have earthquakes," Blakeman said. "Places like Mexico, California and Japan are really beautiful places to live because the tectonic plates keep moving and they make mountains and beautiful seascapes, but earthquakes come with this beautiful scenery and that's the way it is." (AP)