SANTA CATALINA ISLAND, Calif -- A pair of undersea earthquakes struck the sea floor near San Nicolas Island, 55 miles southwest of Point Fermin, U.S. Geological Survey seismologists reported Sunday.

The first undersea quake was a magnitude 4.3, and struck at 2:45 p.m., seismologists said. It was felt as a low, loud rumble in West Los Angeles.

A second, magnitude 3.6 quake struck almost the exact same spot three minutes later, the automated seismic data reported.

Preliminary, automated data from the USGS placed both epicenters about 14 miles east of San Nicolas Island, and 56 miles west of Avalon on Santa Catalina Island, in an area where the sea floor is about 2,000 feet below the surface.

A sheriff's dispatcher in Avalon said he did not feel the quakes. The first quake was originally reported by automated equipment as magnitude 4.5, but human review lowered the magnitude to 4.3.