Geological Summary for New Zealand Area, December 2006

Earthquake activity continued at a low level. White Island, Mt Ngauruhoe, and Mt Ruapehu remained at Alert Level 1.

Geonet, the USGS (NEIC) and IGNS reported 22 earthquakes in the New Zealand area between the Kermadec Islands in the north, and the Auckland Islands to the south during December 2006. The magnitude distributions were as follows:
M6 to 6.9 (1), M5 to 5.9 (1), M4 to 4.9 (8) M3 to 3.9 (10).
An additional 2 events in the magnitude 2 range were deemed worthy of mention.

Three earthquakes struck 20 km north-west of Kawerau in the Bay of Plenty area during December. The quakes were all 5 km or less in depth, with magnitudes between 2.4 and 4.0.

The swarm of earthquakes near Matata continued at a low level, with four further quakes during December. The shallow earthquakes struck 10 km north-east of the town at depths of 5 km or less. Magnitudes ranged between 2.8 and 3.4.

The strongest quake in the New Zealand area during December was a magnitude 6.5 event at a depth of 33 km, west of L’Esperance Rock in the Kermadec Islands on the 27th.

The strongest on-shore quake was a magnitude 5.1 earthquake located 10 km north of Matawai at a depth of 40 km on December 5th. Goods were reportedly thrown from shelves at Whakatane and Opotiki by this event.

Vulcanologists reported the nation’s volcanoes to be quiet during December 2006.

Raoul Island has been downgraded to alert 0 and remains quiescent.

White Island remained at Alert Level 1 with seismic activity low, and the crater lake level dropping due to evaporation.

Mt Ngauruhoe was at Alert Level 1 with the small volcanic earthquakes continuing at a steady rate.

Mt Ruapehu also remained at Alert Level 1 but with very little seismic activity as the crater lake temperature increased slightly.

[Compiled from data supplied by GNS Science, US Geological Survey, Geonet, Hazard Watch and their contributing agencies.]

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