5.9 magnitude earthquake hits New Zealand:Tsunami alert issued; no casualties reported

A tsunami warning in New Zealand has been downgraded to an advisory after a magnitude-5.9 earthquake, according to ABC News. The earthquake struck about 40km north of Te Anau, with the west coast of the South Island, from Milford Sound to Puysegur Point, initially identified as the area most likely to be affected. Emergency officials had first reported the quake as magnitude 6.3 and issued a tsunami warning. The alert has since been reduced to a tsunami advisory. Te Anau is the gateway to Fiordland, a popular tourist region in New Zealand’s south-west, known for its dramatic glacier-carved landscapes. New Zealand’s GeoNet monitoring service said strong shaking was felt across the area following the earthquake, ABC News reported. Meanwhile, the United States Geological Survey (USGS) and the German Research Centre for Geosciences (GFZ) estimated the quake at magnitude 5.9, saying it occurred at a depth of more than 50 km. What are earthquakes? Why do they occur? An earthquake is the sudden shaking of the Earth’s surface caused by the release of energy from within the Earth. This energy release happens due to movements along fault lines, which are fractures in the Earth’s crust. The Earth’s outer shell, called the lithosphere, is divided into large pieces known as tectonic plates that float on the semi-fluid mantle. These plates constantly move, and when they collide, slide past, or pull away from each other, stress builds up. When this stress exceeds the strength of rocks, it is released as an earthquake. The energy from an earthquake travels in the form of seismic waves, which spread out from the epicentre and cause the ground to shake.
The science behind earthquakes The surface of our earth is mainly made up of 7 large and several small tectonic plates. These plates continuously float and sometimes collide with each other. Sometimes the edges of the plates bend due to collision, and when more pressure is applied, these plates start breaking. In such a situation, the energy released from below finds a way out, and after this disturbance, an earthquake occurs.