A strong earthquake measuring 6.0 on the ritcher scale today shook the Pacific island of Vanuatu. The quake hit at a depth of 41 kilometres, 75 kilometres west-northwest of the capital Port Vila. No tsunami warning has been issued. Yesterday's a 7.5-magnitude earthquake had shook buildings in the city for about 15 seconds. Vanuatu, which lies between Fiji and Australia and north of New Zealand, is in the Pacific Ring of Fire known for its seismic and volcanic activity caused by friction between moving plates in the Earth's crust.