Geological Summary for New Zealand Area, January 2009

Earthquake activity declined sharply during January 2009. White Island and Mt. Ruapehu remained at Alert Level 1.

GeoNet, the U.S. Geological Survey and GNS Science reported 38 earthquakes in the New Zealand area between the Kermadec Islands in the north, and the Auckland Islands to the south during January 2009.

The magnitude distributions were as follows:
M6 to 6.9 (1), M5 to 5.9 (8), M4 to 4.9 (7) M3 to 3.9 (13).
An additional 9 events in the magnitude 2 range were deemed worthy of mention.

Earthquake activity during January 2009 was markedly lower than that in December when 51 earthquakes were reported by the USGS and GeoNet. Activity was scattered across both major islands, with only a few areas of note.

Eight earthquakes with magnitudes between 4.7 and 6.4 were reported near Raoul Island during January. The activity was spread from 490 km north to 125 km south of the volcanic island, at depths between 10 and 150 km.

Two deep earthquakes of magnitude 5.1 and 5.0 were reported at locations between East cape and L’Esperance Rock in the southern Kermadecs on the 7th and 11th of January.

Four more earthquakes in the Matata earthquake swarm were reported felt. The quakes ranged in magnitude between 2.5 and 3.2, all located within 10 km offshore from the town at depths of 2 to 5 km.

Opunake hosted a pair of shallow earthquakes of magnitude 3.2 and 3.7 on the 17th and 20th, respectively.

Earthquakes of magnitude 3.3 and 3.6 were reported within 10 km of Porangahau on the 2nd of January.

Regular reporting of the status of New Zealand’s volcanoes ceased at the end of June 2007, with the closure of the Hazard Watch service. GNS Science now only issues bulletins which record significant changes in volcanic behaviour.

No Alert Bulletins were issued by GNS Science during January 2009.

At the end of January 2009, New Zealand’s active volcano status can be summarised as follows:
Raoul Island (Alert Level 0).
White Island (Alert Level 1).
Mt Ngauruhoe (Alert Level 0).
Mt Ruapehu (Alert Level 1).

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

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