A powerful earthquake with a magnitude of 7.8 hit New Zealand just after midnight local time, the largest since 1929 and a tsunami measuring 2 metres in height too hit the northeast coast of the South Island, the U.S. Geological Survey said.
The tsunami hit Kaikoura, 181 km north of Christchurch, and waves are reportedly approaching Wellington and other areas. The Chatham Islands, an archipelago 680 km south-east of the mainland, is being evacuated by authorities.
The earthquake, initially put at 7.4 but later upgraded to 7.8, struck at 12:02 a.m. local time with a depth of 10 km. The quake was felt throughout the country and a series of aftershocks were recorded around the country, some as strong as 6.1 magnitude.
“It was massive and really long,” Tamsin Edensor, a resident of Christchurch, told AFP. “We were asleep and woken to the house shaking, it kept going and going and felt like it was going to build up,” she said.
The Pacific Tsunami Warning Centre, however, said that “a destructive Pacific-wide tsunami is not expected.”
In September 2016, a strong 7.1-magnitude earthquake shook the entire area but no significant damage or injuries were reported. In February 2011, a 6.3 quake hit Christchurch killing 185 people and causing huge damage.
New Zealand is on the boundary of the Australian and Pacific tectonic plates, which is part of the so-called “Ring of Fire”. It experiences almost 15,000 tremors a year.
The USGS said the M 7.8 earthquake in North Canterbury, New Zealand, occurred as the result of shallow oblique-reverse faulting on or near the boundary between the Pacific and Australia plates in South Island, New Zealand.
At the location of this earthquake, the Pacific plate moves to the west-southwest with respect to the Australia plate at a rate of approximately 40 mm/yr.
The plate boundary in the region of the earthquake is complex, involving a transition from subduction along the Hikurangi Trough to the east of the North Island, to transform faulting through the South Island.
The size, depth (~25 km) and faulting orientation of the November 13 event suggest a larger, subduction-related structure, though the subduction zone interface is not thought to extend this far to the south of the Alpine fault system, said USGS in its report.
Today’s earthquake is the largest event in the region since an M 7.3 earthquake 100 km to the northwest in June 1929. Three months prior to it, in March 1929 the Arthur’s Pass strike-slip earthquake, 90 km to the west-southwest of the November 13th event occurred. The Arthur’s Pass event caused damage but injured no one.
The November 13, 2016 event is also about 100 km to the north of Christchurch, which was severely damaged by a series of large earthquakes in 2010-2015, including a M 7.0 to the west of Christchurch in September 2010, and a M 6.1 directly beneath the city in February 2011, said USGS.