Major Quake, Kermadecs

A major earthquake struck the Kermadec Islands this morning.

Thursday 7th July 2011

A magnitude 7.6 earthquake struck 163 km east of Raoul Island at 7:03 this morning. The quake, centred 347 km north-east of L’Esperance Rock (1185 km north-east of Auckland) was 20 km deep. Magnitude 5.6 and 5.3 aftershocks were recorded at 8:36 and 9:04 a.m.

A tsunami was generated by the quake, measuring just over a metre at Raoul Island. The Pacific Tsunami Warning Centre issued three bulletins for the event, initially issuing a warning for New Zealand and Tonga, but this was cancelled at 7:59 a.m. after information from a nearby DART buoy was analysed. This showed that a significant wave had not been generated.

In New Zealand, the tsunami threat has been downgraded to a marine warning, with sea level disturbances likely, but no threat to land is expected. Bathers and small boat owners should stay clear of coastal areas and estuaries, with unusually strong tidal surges and currents possible for the next 24 hours.

GeoNet’s seismograph network on 7 July 2011

[click for larger image] The earthquake showed a strong trace on New Zealand’s seismograph network.

GeoNet shakemap for New Zealand 7 July 2011

[click for larger image] MM5 shaking (green squares) was recorded along the coast from Gisborne to East Cape, with MM4 shaking recorded over most of the North Island. In Gisborne, the earthquake was felt as a rolling motion.

[Compiled from data provided by the GeoNet project and its sponsors EQC, GNS Science and FRST; the US Geological Survey and the Pacific Tsunami Warning Centre.]

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