Now, dam’s vibrations can be used to capture seismic waves

November 18th, 2007 - 12:25 pm ICT by admin  

Washington, Nov 18 (ANI): Geophysicists have found a method to capture seismographs from within the Earth’s crust using the seismic vibrations of a concrete dam in Montana, US.

The dam takes vibrations of other kinds and remakes them into specific, identifiable seismic tones. Then it radiates those tones into the ground, which can be detected by seismographs.

Earlier, seismologists had to wait for an earthquake or set off explosives to create enough vibrations to seismically light up the interior of the Earth for capturing seismographs.

Using a dam’s vibrations for the same purpose is part of a recent trend by scientists to turn to less dramatic vibrations caused by tides, winds, traffic, surf and other such seismic noise to detect the different sorts of rocks and sediments that make up a given part of the crust.

“The Earth is always vibrating in response to various phenomena,” said geophysicist Dan O’Connell, who led the project on the dam.

O’Connell’s task was to evaluate the safety of the ground under the dam in the case of a strong earthquake. To do that, he needed to see what sorts of rocks were in the local crust. The harder the rocks, the faster the seismic waves move and the safer the ground is in an earthquake.

O’Connell decided to use that constant noise as a back up for imaging the structures in the crust around the dam in northwestern Montana, in case no tremor came along to help him out.

But instead of the standard seismic noise, O’Connell decided to try and use vibrations made by the concrete dam itself as it was being rung like a complicated seismic bell by other seismic noises.

“The dam is like a complex tuning fork,” Discovery News quoted O’Connell as saying.

By installing seismic stations both near and away from the dam, O’Connell was able to use the dam’s own seismic noises as a local source of useful vibrations to light up buried structures.

“It allowed me to acquire seismic signals quickly because the dam produced such a strong signal,” said O’Connell.
“I think it’s amazing,” said geophysicist Roel Snieder of the Colorado School of Mines, regarding O’Connell’s use of the dam as a seismic flashlight. “Suddenly you don’t need a controlled source,” he added. (ANI)

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