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U. geophysicist's research helps understand earthquakes

While water on the surface can gouge out mile-deep canyons on the face of the planet, deep underground water flows are tilting broken sections of the world's massive stone foundation into the next big-magnitude earthquake.

Water, according to a three-year study coordinated by a University of Utah geophysicist and published today in the journal Nature, does more than lube the constantly stacking and restacking of the Earth's tectonic superstructure — it tilts then holds massive stone slabs at angles as steep as the roof on a ski chalet.

The process creates rifts and faults in the crust similar to the relatively shallow, quake-inducing San Andreas Fault in California, Phil Wannamaker, lead author of the study, told the Deseret News on Wednesday, noting that water and fluids trapped 10 to 20 miles underground have been regarded as lubricants to tectonic shifting.

"Science understands how the Earth's moving tectonic plates can dive or subduct beneath another to create earthquake-generating faults, but that the fluid-related processes involved would reach up and cause damage right under our feet hasn't really been on people's minds," Wannamaker said.

The study focused on the geologically adolescent, seismically hyperactive zones in the Ring of Fire near New Zealand. The country sits on the boundary between two of Earth's slowly moving tectonic plates and regularly features big earthquakes and active volcanoes.

Using a new method of detecting electromagnetic waves normally too faint to matter, Wannamaker and colleagues from Japan and New Zealand made measurements at 67 sites along a 125-mile line crossing the northern end of New Zealand's South Island. They found the first measurable evidence that fluids force up and support the vertical shifts as well as facilitate the horizontal movement of the plates.

The data is a breakthrough in part for what it shows and where it was gathered — a part of the planet too far down to drill to — can't be photographed and generally eludes normal scientific research methods.

The processes revealed by the study are significant, Wannamaker said, "because tectonic plates (that) can dive or subduct beneath another to create earthquake-generating faults are major geologic activities all over the world."

e-mail: jthalman@desnews.com