Powerful 7.6 earthquake rattles Costa Rica.

CBS/AP) NOSARA, Costa Rica - A powerful, magnitude-7.6 earthquake shook Costa Rica and a wide swath of Central America on Wednesday, collapsing some houses, blocking highways and causing panic. Reuters reported of two deaths, one of those from a heart attack, according to a spokesperson for the local Red Cross.
The U.S. Geological Survey said the quake was centered about 38 miles from the town of Liberia. The magnitude initially was estimated at 7.9, but was quickly downgraded. Local residents said it shook for about 30 seconds.
While officials cancelled an initial tsunami warning, local police supervisor Jose Angel Gomez said about 5,000 people -- 80 percent of the population -- had been evacuated from coastal towns in the Samara district west of the quake's center several hours after the quake struck at 8:42 a.m. (10:42 a.m. EDT; 1442 GMT). He said water was receding from the shore.One man died of a heart attack caused by fright, said Carlos Miranda, a Red Cross worker in the city of Liberia, but there were no reports of deaths directly caused by the quake.
In the town of Hojancha a few miles from the epicenter, city official Kenia Campos said the quake knocked down some houses and landslides blocked several roads.
"So far, we don't have victims," she said. "People were really scared ... We have had moderate quakes but an earthquake (this strong) hadn't happened in more than 50 years."
A preliminary review revealed some structural damage near the epicenter, but no deaths or injuries, said Douglas Salgado, a geographer with Costa Rica's National Commission of Risk Prevention and Emergency Attention.
The review also uncovered a landslide on the main highway that connects the capital of San Jose to the Pacific coast city of Puntarenas, Salgado said. Hotels and other structures suffered cracks in walls and saw items knocked off shelves.
"There's chaos in San Jose because it was a strong earthquake of long duration," Salgado said. "It was pretty strong and caused collective chaos."
Ana Zuniga Alvarez, a waitress at the Hacienda del Sol hotel between Nosara and San Juanillo, very near where the epicenter was, said there were no deaths or injuries at the hotel and no damage.
The hotel was closed at the time, but the staff were working when the quake struck. Other than some items falling from shelves, the worst part of the earthquake was "the scare," she told CBS News.
Michelle Landwer, owner of the Belvedere Hotel in Samara, north of the epicenter, said she was having breakfast with about 10 people when the earthquake struck.
"The whole building was moving, I couldn't even walk," Landwer said. "Here in my building there was no real damage. Everything was falling, like glasses and everything."
Rosa Pichardo, 45, who lives in Samara, was walking on the beach with her family when the quake hit.
"When we felt the earthquake, we held onto each other because we kept falling," Pichardo said. "I've never felt anything like this. We just couldn't stay standing. My feet gave out under me. It was terrible, terrible."
At the Hotel Punta Islita in the Guanacaste area, "everybody is crying a lot and the telephone lines are saturated," said worker Diana Salas, speaking by telephone, but she said was no damage there.
In the coastal town of Nosara, roughly 50 miles north of the epicenter, trees shook violently and light posts swayed. Teachers chased primary school students outside as the quake hit. Roads cracked and power lines fell to the ground.
Wednesday's quake occurred in a seismically active zone where the Pacific tectonic plate is diving beneath Central America.
"All along the Pacific coast of Central America, you can expect fairly big earthquakes," said seismologist Daniel McNamara of the U.S. Geological Survey.
The quake was fairly deep -- 25 miles below the surface. Deeper events tend to be less damaging than ones closer to the surface, but more widely felt.
"If it was a shallower event, it would be a significantly higher hazard," he said.
The last deadly quake to strike Costa Rica was in 2009, when 40 died in a magnitude-6.1 temblor. The last similar-sized quake to hit the country was in 1991 when 47 people were killed in the Limon-Pandora area.
While there was no immediate evidence of tsunami waves, a regional warning was issued based on the quake's strength.
"We're erring on the side of caution until we know for sure," said Mike Angove, acting director of the tsunami program at the National Oceanic and Atmospheric Administration.