SOUTH PADRE ISLAND, Texas — A small earthquake has been detected off the coast of South Texas.

The U.S. Geological Survey says the rare 3.0 magnitude temblor Saturday afternoon northeast of South Padre Island in the Gulf of Mexico likely wasn't felt by many people.

An agency geophysicist, Jana Pursley, tells the Corpus Christi Caller-Times the quake occurred at the edge of the continental shelf but it's uncertain what happened. She says it's possible "something shifted."

Pursley says earthquakes in the Gulf of Mexico are not common and usually occur farther south near Mexico.

Four similar quakes have been reported off the Texas coast since 1973.