A powerful undersea quake measuring 6.5 on the Richter scale rocked Java island of Indonesia on Saturday and caused damage to houses, but with no potential for tsunami, officials said here. The quake rattled at 12:14 p.m. Jakarta time (0514 GMT), with epicenter at 104 km southwest of Central Java and depth at 48 km under seabed, an official of the Meteorology and Geophysics Agency told Xinhua by phone. The shake was also felt at West Java and Yogyakarta, driving panic and forcing people to rush out of houses and buildings, the official and spokesman for national disaster agency Sutopo Purwo Nugroho said. The intensity of the quake was recorded at 3 to 4 MMI (modified mercalli intensity) at Pemalang, Purwokerto of Central Java, and 2 to 3 MMI in Pangandaran, Bandung city and 3 MMI at Tasikmalaya of West Java, the meteorology official said. Two aftershocks measuring 4.9 and 4.3, respectively, on the Richter scale followed the main shock, also centering at seabed, he said. "One house collapsed and several others suffered from damages in Krangdegan village at Purworejo (Central Java)," Sutopo told Xinhua, adding that further assessment was being conducted in the area and other quake-affected areas. "In Yogyakarta, Cialacap and Kebumen, people were panic and quickly left their houses and office buildings," he said. Indonesia is vulnerable to seismic upheaval as it sits on the so-called Pacific Ring of Fire, an arc of volcanoes and fault lines surrounding the Pacific Ocean