New Zealand authorities on Thursday lifted the tsunami warning issued after a 5.9-magnitude earthquake struck off the west coast of the South Island, saying the threat had eased following a revised assessment of the quake.New Zealand downgrades tsunami alert after earthquake. (REUTERS)The National Emergency Management Agency said the advisory had been downgraded from a warning after determining that the earthquake was smaller than initially estimated, news agency AFP reported.Also read | New Zealand reports first case of deadly H5N1 bird flu virus in sea birdAuthorities, who had earlier urged people in affected coastal areas to "move immediately" to higher ground, later advised residents to remain cautious of "strong and unusual currents" along the shoreline.Initial warning prompted evacuationsSoon after the earthquake, emergency officials had asked people in affected coastal areas to "move immediately" to higher ground as a precaution.Also read | India a launchpad for global growth, PM Modi tells New Zealand investorsThe earthquake struck at a depth of 76 kilometres, about 83 kilometres west of Queenstown, a popular tourist destination on the South Island, according to the US Geological Survey (USGS).Authorities also warned of possible land inundation and instructed people in Milford Sound, another major tourist hotspot, to evacuate to higher ground.Residents describe strong shakingPeople living in the region described experiencing a powerful jolt.The manager of a hotel in nearby Te Anau told AFP she "could hear it coming first".Also read | India, New Zealand forge ₹35,000 crore strategic partnership to boost trade"The shaking was very severe. I thought it was the big one we've been told is coming."Despite the strong tremors and precautionary evacuations, no damage had been reported by Thursday night.Why New Zealand frequently experiences earthquakes?New Zealand frequently experiences earthquakes because it sits at the boundary of the Australian and Pacific tectonic plates. The country is also prone to volcanic activity.Earlier on Thursday, a separate 5.0-magnitude earthquake was felt off the North Island.The country has witnessed devastating earthquakes in the past. In 2011, a 6.3-magnitude quake struck Christchurch on the South Island, killing 185 people.(With AFP inputs)