Massive Fiordland quake triggers tsunami alert

A magnitude 7.8 earthquake off the coast of Fiordland last night has made international headlines.

Image credit: GeoNet
Image credit: GeoNet

The quake occurred at 9:22 pm on 15 July, and was followed by two large aftershocks.

The shaking was felt throughout the South Island and as far north as Wellington and the lower North Island. No major damage or casualties have been reported.

The tremors triggered an alert from the Pacific tsunami warning centre for both New Zealand and eastern Australia. After large waves failed to materialise, the alert was cancelled around 11 pm.

Sensors showed a small tsunami was generated, but caused a sea level increase of only 17 cm at the nearest monitoring station to the quake, located at Jackson Bay in Westland.

What happened, why alert downgraded

Bill Fry, GNS Science duty seismologist comments:

“After the preliminary magnitudes for earthquake came in, an automated warning was set off by Pacific Warning Centre.  We were in communication with civil defense and agreed there should be an advisory of possibility of tsunami.  We had some scenarios for what might be expected based on knowing the variability of these things, and then a gauge that measured 17cm height for the tsunami, at which point the advisory was withdrawn.

“The warning system has been up for the better part of a year, and there was another one for an earthquake north of the north island some 4 months ago – it was also stood down.

“Last night was a very good test for the warning system and a very good example that it was working.”

News coverage:

Radio New Zealand: Little damage reported after 7.8 quake
NZ Herald: Checks for damage after big quake rocks south
NZ Herald (NZPA) :Quake ‘so long it made me feel seasick’ Magnitude 7.8 quake hits Southland
Otago Daily Times: ‘The whole house was moving’
The Dominion Post: Quake would have devastated Wellington
The Press: Strong earthquake rattles South Island
The Timaru Herald: Quake shakes South Island
TVNZ (AAP): Aust faces more tsunami threats due to NZ quakes
TV3 News: Effects of 7.8 quake felt in Australia
NewsTalk ZB: Quake damage minor so far

ABC News: Tsunami threat fizzles out
Sydney Morning Herald: Tsunami alert after NZ earthquake
Herald Sun: Quake rattles NZ

Associated Press: Tsunami warnings cancelled after 7.8 quake off NZ
Associated Press: 7.8 quake strikes off NZ; small tsunami generated
BBC: Quake sparks NZ-Australia alert
CNN: Major quake strikes off New Zealand
Bloomberg: NZ Tsunami warning dropped after magnitude-7.8 quake
Telegraph UK: Tsunami warning in New Zealand after undersea earthquake
The Daily Telegraph: Tsunami alert for east coast of Australia
The Daily Telegraph: Australian tsunami alert scaled back