Matata Swarms Enter New Phase

GeoNet has published a brief report on the earthquake swarms at Matata, and advise that the sequence of quakes has entered a third phase of activity.

GeoNet now consider that the swarms of quakes near Matata have shown three distinct phases. The first phase occurred between January and December of 2005, when about 1000 quakes were analysed to determine their location. During phase 1, only one of the earthquakes registered over magnitude 4.

During the second phase, represented by swarms of earthquakes that commenced in December 2006, about 1200 earthquakes were analysed. This phase included six earthquakes of magnitude 4 or greater between March and May of 2007 and another 5 events over magnitude 4 during October, when a lot of energy was released.

Activity virtually ceased early in November of this year and the swarm then entered a new phase.

Since the early part of November, nearly 100 earthquakes have been identified, clustered around a position off-shore from Matata. This third phase indicates that activity has moved off-shore and means that residents of Matata and nearby towns will feel fewer earthquakes.

The earthquakes are occurring because the Taupo Volcanic Zone is being slowly pulled apart by tectonic forces, causing the distance between the Coromandel Peninsula and East Cape to increase by about 10 mm each year. The movement occurs in abrupt steps, which we feel as earthquakes, when the earthquake faults in the area react to the altered stress.

The Matata earthquake swarms are one of many features that make the Taupo Volcanic Zone, which covers the area from Mt. Ruapehu to White Island, a unique and fascinating place. The zone also features dormant and active volcanoes and more than 20 geothermal systems, some of which have been developed as tourists areas, while others are harvested for energy use.

The stretching of the area means that the Earth’s crust is thinner than normal throughout much of the zone, and is only about 10 km deep. Not only are tourists fascinated by the features of the Taupo Volcanic Zone, but scientists from around the world regularly visit to study aspects of its activity. Not surprisingly, New Zealand’s seismologists and vulcanologists spend a lot of time in the area, and GNS Science has installed a new permanent site just to the west of Matata to improve the collection of information on the area’s earthquake activity.

Maps and plots of the Matata quakes over time have been included in the report on the GeoNet website.

[Compiled from data provided by the GeoNet project and its sponsors EQC, GNS Science and FRST.]

2 Responses to “Matata Swarms Enter New Phase”

  1. Flying Deldas says:

    Sitting at the dining room table 5.24 this evening and felt the table moving to and fro in front of me. Bob standing at the kitchen sink couple of metres away was not aware of anything even when I drew his attention to what I was feeling. Not sharp but seemed to go for about several seconds and I knew it was a quake.

  2. Devin Mynett says:

    Is it my imagination but are these events getting less and less deep in origin?

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