UPDATE 1-Shallow quake of magnitude 6.5 strikes off Puerto Rico - USGS

An earthquake of magnitude 6.5 struck just off Puerto Rico at a shallow depth of 10.0 km in the early hours of Tuesday, the US Geological Survey reported on Tuesday, in a slight downward revision of its first reading.

The Pacific Tsunami Warning Center said there was "no significant tsunami threat", but a "very small possibility of tsunami waves along coasts located nearest the epicenter". The epicenter of the quake, which struck at 4:24 am (0824 GMT), was five km (three miles) south of Tallaboa, near Ponce on the island's southern coast, the USGS said.

It was the largest in a series of quakes that have struck the area over the past two weeks. "It was super strong. I could hear the vibrations everywhere." one witness located 14 km (nine miles) from the epicenter posted on the European Mediterranean Seismological Centre website. Another witness in Caimital, 67 km away, said the quake lasted around 30 seconds.

A 5.8-magnitude earthquake off southern Puerto Rico on Monday knocked several houses off their supporting pillars in the towns of Guanica and Guayanilla. Television images showed vehicles crushed beneath them. That quake also destroyed the Window of the Caribbean, a rock formation on a beach that had been a tourist attraction, but there were no reports of injuries. (Writing by Kevin Liffey; editing by John Stonestreet)