An earthquake measuring 5.4 on the Richter scale jolted Sumatra island on Friday, the Meteorology and Geophysics Agency reported here. The quake struck at 11 : 34 a.m. Jakarta time (0434 GMT) with epicenter at 321 km southwest Simeulu of Aceh province and with the depth at 27 km, the agency said. Indonesia sits on a vulnerable quake-hit zone where is called \"the Pacific Ring of Fire.\"