An earthquake with magnitude of 5. 5 jolted western Java island on Saturday, the meteorology and Geophysics Agency reported here. The quake struck at 6:17 a.m. Jakarta time Saturday (2317 GMT Friday) with epicenter at 636 km southwest Ujungkulon of Banten province and with the depth at 10 km under sea bed, an official of the agency told Xinhua. Indonesia is vulnerable on earthquake as it sits on a vulnerable quake-hit zone so called \"the Pacific Ring of Fire,\" where two continental plates, stretching from Japan to western hemisphere, meet that frequently caused seismic and volcanic movement in the country homed by 129 active volcanoes.