An earthquake of 5.7 magnitude jolted East Nusa Tenggara in central Indonesia on Saturday, the meteorology and geophysics agency said.The quake struck 16:11 p.m. Jakarta time (0911 GMT) with the epicenter at 48 km northwest Sumba Timur and an depth of 77 km under earth, an official of the agency told Xinhua by phone.Indonesia is prone to quake as it lies on a vulnerable quake-hit zone, the so called "the Pacific Ring of Fire".Source: BSS