An earthquake measuring 5.1 on the Richter scale hit the waters southwest of Nias Island in North Sumatra province on Sunday, ANTARA reported. The epicenter of the quake which struck at 9.59 a.m. was located 74 km southwest of Gunung Sitoli, the capital city of Nias Island, in a depth of 17 km, the Meteorology and Geophysics Agency (BMG) said on Sunday. The quake did not have the potential of causing a tsunami, it said.