SYDNEY : A powerful earthquake with a magnitude of 7.5 struck off the Solomon Islands Sunday night, hours after a 7.6 tremor, the US Geological Survey said.A tsunami warning has been issued for the Solomon Islands, Vanuatu and Papua New Guinea, the Pacific Tsunami Warning Center said.The Center said the warning was issued based on the magnitude of the quake, and is was not known whether a tsunami had in fact been generated.The USGS said the quake - which it had initially assessed at 7.7 - occurred at 11.36 pm local time (12.36 GMT) at a depth of 35 km (22 miles), 111 km south of Kirakira in the Solomon Islands. It said the likelihood of casualties or damage was low. A 7.6 magnitude quake had woken the residents of the Solomons capital Honiara early Sunday. It struck at 7:14 am, about 300 kilometres from the capital, and was followed 10 minutes later by a 5.9-magnitude aftershock.The US Geological Survey measured the undersea quake at around 29 kilometres deep. Honiara resident Dorothy Wickham said the National Disaster Council was warning people to stay away from low-lying areas as the islands experienced high waves.“People are moving away from the coasts and are going up into the hills, but I have not heard of any damage,” she said.The Intergovernmental Oceanographic Commission put out a tsunami warning for the Solomon Islands, Vanuatu and Papua New Guinea following the Sunday morning quake, but later cancelled the alert.The Solomons were hit by flash floods 10 days ago which left more than 20 dead. Several more are still missing in Honiara after the city’s main river burst its banks following days of heavy rain.The Solomons are part of the “Ring of Fire”, a zone of tectonic activity around the Pacific that is subject to frequent earthquakes and volcanic eruptions.A 6.1-magnitude tremor hit the Solomons on Saturday and a powerful 7.1-magnitude earthquake and 6.7 aftershock struck off Papua New Guinea’s Bougainville island on Friday, to the west of the Solomons.In February last year, the Solomon Islands were hit by a major 8.0 magnitude quake that generated small but deadly tsunami waves which washed away houses and reached as far away as Japan.In 2007, a tsunami following an 8.0-magnitude earthquake killed at least 52 people in the Solomons and left thousands homeless.The quake lifted an entire island and pushed out its shoreline by dozens of metres.