Strong Quake, Southern Kermadecs

A strong, undersea earthquake struck the southern Kermadec Islands last night.

Saturday, 8th October 2011

A magnitude 6.1 earthquake struck 106 km south of L’Esperance Rock in the Kermadec Islands (762 km north-east of Auckland) at 9:58 p.m. New Zealand Daylight Time last night. The undersea quake was 40 km deep according to the U.S. Geological Survey.

Geoscience Australia reported the earthquake as magnitude 6.0 at a depth of 7 km, estimating that it would have been felt within 460 km of the epicentre.

GeoNet Seismograph Network 7th October 2011

[Click for larger view] The quake showed a strong trace on New Zealand’s seismograph network.

GeoNet New Zealand shakemap, 7 October 2011

[Click for larger image] GeoNet’s shake map, using data from New Zealand seismographs, indicated that shaking intensity reached MM5 (sleepers awakened, small objects shifted or overturned, pictures knock against the walls) at Matata and near Tokomaru Bay.

Lighter MM4 shaking was recorded along coastal areas of Gisborne, Hawke’s Bay and Wairarapa where windows, doors, glassware and crockery may have been heard to rattle.

GeoNet did not report the event, so there is no indication of the extent to which the quake was felt in New Zealand. The U.S. Geological Survey received two reports from New Zealand, one from Franz Josef, the other from Christchurch. Both reported weak shaking.

A magnitude 4.8 aftershock centred 182 km south-east of L’Esperance Rock at 1:15 this morning, was reported by the U.S. Geological Survey.

GeoNet Seismograph Network, 8 October 2011

[Click for larger image] GeoNet’s seismograph network showed the traces of the main shock and what appear to be two aftershocks early this morning.

The Pacific Tsunami Warning Centre did not report the event.

[Compiled from data provided by the GeoNet project and its sponsors EQC, GNS Science and FRST; the US Geological Survey, and Geoscience Australia.]

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