Trapped Fluid May Cause Earthquakes
Matt Torbit and NZPA-The Dominion Post
The recognition was particularly pleasing as only about 10 per cent of the scientific papers offered to the journal are accepted for publication.
The GNS study is the first to produce three-dimensional images of the layers of the Earth's crust at the time when quakes were tearing it apart, they said.
The earthquakes in the lower crust happen at a depth of 15 kilometres to 40km under the Taupo Volcanic Zone, and have long puzzled seismologists, as at that depth the crust has always been thought too hot to break in the brittle fashion that occurs during earthquakes.
Most of the 5000 quakes in the lower crust - measured over a two-week period in 2001- were at the southern end of the Taupo Volcanic Zone, close to Mt Ruapehu, and most were too small to have been felt on the surface. The researchers put in a network of seismographs closely spaced around the Taupo Volcanic Zone and their recordings were used to construct three-dimensional images of the crust - similar to the way a medical CAT scan can show the inside of the human body.
These images showed pockets of fluids that were collecting in underground fault-line gaps.
The scientists' theory was that the trapped fluid acted as "lubrication" for further fault-line slips and subsequent earthquakes.
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