Strong Quake, Central North Island

A strong earthquake struck the central North Island this afternoon.

Tuesday, 5th July 2011

A magnitude 6.5 earthquake struck 30 km west of Taupo at 3:36 this afternoon. The 150 km-deep quake was widely felt in both the North and South islands from Auckland to Dunedin, causing tall buildings in Wellington to sway noticeably.

The quake occurred in the cold slab of the Pacific tectonic plate deep under the central part of the North Island.

GeoNet Seismograph Network 5 July 2011

[click for larger image] The quake’s strength and depth meant that it left strong traces on GeoNet’s seismograph network.

Instrument shaking recorded after the magnitude 6.5 quake

[click for larger image] GeoNet’s instruments showed shaking reached MM6 (yellow squares) along the eastern coast of the North Island, in parts of the Bay of Plenty and Taranaki, at Wanganui and in Wellington’s Hutt Valley. MM6 shaking is classified as slightly damaging and described as: “Felt by all. People and animals are alarmed, and many run outside. Walking steadily is difficult. Furniture and appliances may move on smooth surfaces, and objects fall from walls and shelves. Glassware and crockery break. Slight non-structural damage to buildings may occur.”

Shaking reached MM5 intensity over much of the North Island and in northern parts of the South Island. Under these conditions, small objects are shifted or overturned, and pictures knock against the wall. Some glassware and crockery may break, and loosely secured doors may swing open and shut.

The U.S. Geological Survey reported the earthquake as magnitude 5.3. Its analysis puts the epicentre 69 km south-west of Rotorua, 144 km north-west of Napier, at a depth of 161 km.

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

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