Major Quake, Kermadecs

A major undersea earthquake struck near Raoul Island in the Kermadec Islands this morning.

Saturday, 22nd October 2011

A shallow magnitude 7.3 earthquake struck 230 km east of Raoul Island (310 km east of Macauley Island) in the Kermadec Islands at 6:57 this morning, New Zealand Daylight Time, according to GeoNet.

The undersea quake generated a small tsunami, measured at 17 cm at Fishing Rock on Raoul Island, according to the Pacific Tsunami Warning Centre. The PTWC reported the quake as magnitude 7.4 at a depth of 40 km.

The U.S. Geological Survey reports the quake as magnitude 7.4 at a depth of 33 km, centred 170 km east of Raoul Island.

Geoscience Australia reports the quake as magnitude 7.3 at a depth of 35 km. It estimates that it would have caused damage within 130 km of the epicentre and would have been felt up to 1700 km away.

GeoNet’s seismograph network 22 October 2011

[click for larger image] The earthquake registered a strong trace on New Zealand’s seismograph network. GeoNet reports that the quake was felt along the eastern coast of New Zealand from Auckland to Geraldine, and as far west as Taneatua in the Bay of Plenty and Collingwood in Tasman district in the South Island.

The Pacific Tsunami Warning Centre issued two bulletins for the event, determining that a tsunami threat did not exist for the Pacific after the 17 cm wave had been recorded at Raoul Island.

The Ministry of Civil Defence and Emergency Management issued a potential tsunami threat warning at 8:49 a.m. and activated the National Crisis Management Centre. It issued a second bulletin at 9:35 a.m. cancelling the advisory after the measurements at Raoul Island had been analysed. It also noted that the clean-up and salvage work associated with the container ship Rena’s stranding in the Bay of Plenty should not be affected by the event.

Today’s earthquake follows a strong magnitude 6.1 earthquake south of L’Esperance Rock in the southern Kermadecs on October 7th. Quakes of magnitude 4.8 and 5.0 have been reported in the Kermadecs during the past week.

[Compiled from data provided by the GeoNet project and its sponsors EQC, GNS Science and FRST; the U.S. Geological Survey, the Pacific Tsunami Warning Centre, Geoscience Australia, and the Ministry of Civil Defence and Emergency Management.]

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