Antonio Manaytay – Fourth Estate Contributor
Salt Lake City, UT, United States (4E) – Researchers from the University of Utah have discovered that the gentle waves of a lake can trigger tremors underneath sending ripples to earth, which can only be perceived with an aid of seismometers.
These small but constant tremors could help determine the cycle of freezing and thawing of a lake, the scientists said in a study published in the Journal of Geophysical Research Solid Earth.
“It’s kind of a new phenomenon,” study co-author Keith Koper said.
Koper, who is also the director of the University of Utah Seismograph Stations, said they had no idea yet “how it’s created.”
These tremors, according to Koper, are so small that are imperceptible by human senses.
“You won’t be able to feel ’em,” he said. But these small tremors can be recorded when they are observed over a long period, he added.
Ocean waves have been known to generate microseisms – small seismic waves that are produced when waves interact or drag across the bottom of the ocean. It explains why seismic noise is heard along the coasts.
“We’ve recently found that the waves on lakes actually generate these microseisms, too,” Koper said.
These microseisms are recorded in Great Lakes, Canada’s Great Slave Lake, and the Great Salt Lake in Utah. Similar observations were recorded in Yellowstone Lake and at least three other lakes in China.
These microseisms, which could be a source of seismic energy, could give new information on the geology around the lake in what Koper termed as seismic tomography or “CT scan of the Earth.”
Observing how these waves change, according to Koper, as they ripple through the earth at varying speed can greatly aid in determining the geologic structures nearby the lake.
These seismic signals can be created by several means: an explosion, a hammer on a metal plate, or a vibrating plate outfitted on a truck.
“It would take quite a bit of effort and work to generate this level of energy,” he said.
These seismic signals can also aid in determining the freezing and thawing of lakes instead of relying on satellite observations, geology major Aini Mokhdhari said.
The seismic tremors, created by waves driven by the wind, could serve as an autonomous seismometer to monitor the freezing and thawing of the lake.
The data gathered from Yellowstone Lake, which freezing and thawing are known, had confirmed Mokhdhari’s observations.
Mokhdhari is set to present the study’s findings during the Fall Meeting of the American Geophysical Union to be held in New Orleans on December 11-15.
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