NOSARA, Costa Rica (AP) - A powerful, magnitude-7.9 earthquake shook Costa Rica on Wednesday. There were no immediate accounts of damage or injuries.
    
The USGS said the 8:42 a.m. quake struck offshore, about 50 miles (80 kilometers) from the town of Liberia.
    
In the coastal town of Nosara in northwest Costa Rica, trees shook violently and light posts swayed. Teachers chased primary school students outside.
    
A tsunami warning was in effect for Costa Rica, Panama, Nicaragua, El Salvador, Honduras, Mexico, Colombia, Ecuador, Guatemala and Peru and a tsunami watch was in effect for Chile, the Pacific Tsunami Warning Center said in a bulletin.  It said it was unknown if a tsunami was generated, but the warning was based on the size of the earthquake.

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