An earthquake with a magnitude of 6.0 struck off the Mexican Pacific coast late Sunday, US researchers said, but there were no immediate reports of casualties or damage. The epicenter of the quake, which occurred at 11:26 pm Sunday (0626 GMT Monday), was located in the Gulf of California 73 kilometers (45 miles) southwest of the Mexican town of Topolobampo, the US Geological Survey reported. The earthquake reading was based on the open-ended Moment Magnitude scale used by US seismologists, which measures the area of the fault that ruptured and the total energy released.