Massive, shallow quake rocks southern Mexico

Mexican President Felipe Calderon expressed relief on his Twitter account that no serious damage had been reported from Tuesday's quake.
"It was a very big scare, but luckily, we have no reports of major damage," Calderon said.
The US Geological Survey reported the quake at magnitude 7.4, lowered from an initial estimate of 7.6. It struck at 12:02 pm (1802 GMT) with an epicentre in the state of Oaxaca on the Guatemalan border.
Mexico's National Seismological Service estimated the magnitude at 7.8 with the epicentre south of Ometepec, a city of 50,000 in the state of Guerrero, about 190 kilometres east of the Pacific resort of Acapulco.
At least five people were injured in the state of Oaxaca, Governor Gabino Cue said.
"I have a report from Pinotepa of five people injured, one of them seriously, a police officer who was hit by a falling billboard," Cue said.
About 500 homes were damaged in Guerrero, mainly in the municipalities of Costa Chica and La Montana.
"Fortunately, the report we have so far is that there have been no deaths or human losses," Guerrero Governor Angel Aguirre said.
Aguirre said authorities were flying over the quake zone to assess damage.
Large tremors were felt more than 300 kilometres away in Mexico City, sending thousands of people pouring into the streets from tall buildings. A pedestrian bridge in the capital collapsed onto an empty minibus.
Telephone service was cut. There were partial blackouts, and goods tumbled from store shelves. Tiles and mirrors fell, and some walls cracked or collapsed even in the capital.
The quake affected traffic, particularly in areas where traffic lights malfunctioned.
After the tremor, Civil Protection officials authorized access to public buildings floor by floor.
Mexico City Mayor Marcelo Ebrard said the sprawling capital's subway and its airports were operating normally.//DPA