Thursday, March 8, 2012

Seismic signals produced by tornado

Posted by on Thu, Mar 8, 2012 at 9:30 AM

A graphic shows the location of seismographs in eastern Missouri and southern Illinois and the path of the tornado that struck Harrisburg, Ill., on Feb. 29. - MAP COURTESY OF INDIANA UNIVERSITY
  • Map courtesy of Indiana University
  • A graphic shows the location of seismographs in eastern Missouri and southern Illinois and the path of the tornado that struck Harrisburg, Ill., on Feb. 29.

Editor's Note: We received the following news release from I.U. this morning:

An Indiana University geophysical experiment detected unusual seismic signals associated with tornadoes that struck regions across the Midwest last week - information that may have value for meteorologists studying the atmospheric activity that precedes tornado disasters.

The experiment by IU researchers involves deployment of more than 100 state-of-the-art digital seismographs in a broad swath of the U.S. midcontinent. One of the twisters that struck southeastern Missouri and southern Illinois on Feb. 29 passed through the seismic detection array.

"In examining the seismograms, we recorded unusual seismic signals on three of our stations in southern Illinois," said Michael Hamburger, professor in the department of geological sciences at IU Bloomington and one of the researchers conducting the experiment.

"The seismograms show a strong, low-frequency pulse beginning around 4:45 a.m. on Feb. 29. Our preliminary interpretation, based on other seismic records of tornadoes, suggests that we were recording not the tornado itself, but a large atmospheric pressure transient related to the large thunderstorms that spawned the tornadoes."

The seismographs that detected the pulse are near Harrisburg, Ill., a town of 9,000 where a pre-dawn twister caused extensive damage, killed six people and injured about 100 more.

IU researchers initially feared that some of the instruments might be damaged by the storm, setting back a National Science Foundation-funded project that included the investment of hundreds of thousands of dollars and months of effort. But when principal investigator Gary Pavlis, an IU professor of geological sciences, checked the digital recordings of the Illinois stations on Feb. 29, he found they were still alive and streaming data. As he checked further, he discovered the strange "tornado seismograms" that were recorded on seismographs near Harrisburg.

Hamburger said a seismic pressure gradient associated with the tornado produced a slow, minute tilting of the seismograph that lasted for several minutes. He said this sort of pressure-related signal may help scientists better understand atmospheric activity that takes place right before tornadoes touch down. The IU researchers are working with colleagues at the University of California San Diego to try to compare recordings with other tornado-related signals and to dig deeper into the analysis.

While seismographs have been known to detect seismic activity related to tornadoes, it is highly unusual to have state-of-the-art digital instruments recording information in such close proximity to a tornado, the researchers say. The IU seismic experiment, dubbed "OIINK" for its geographic coverage in parts of the Ozarks, Illinois, Indiana and Kentucky, includes the positioning of 120 seismometers to study earthquakes and geological structure in a key area of North America. Installation of the instruments began last summer. They are recording thousands of earthquakes from the study area and around the world, as well as nearby mining and quarry explosions.

The $1.3 million, four-year undertaking is part of the NSF's EarthScope program, which seeks to cover the entire U.S. with a grid of detection devices for the purpose of better understanding seismic activity and predicting earthquakes. Researchers liken EarthScope to "an upside-down telescope" that allows them to look into the Earth and gain a better understanding of seismic forces.

Tags: , , , , , ,

Speaking of...

  • Big Ten Men's Basketball Tourney Round 1
  • Big Ten Men's Basketball Tourney Round 1

    Indianapolis played host to the 2014 Big Ten Men's Basketball Tournament, opening Thursday as the lower seeds battle Round 1.
    • Mar 14, 2014
  • Ask the Sex Doc: Episode 3
  • Ask the Sex Doc: Episode 3

    This week, the ladies talk about the latest in pubic fashions, cuckolding for two, and something called "postcoital blues."
    • Feb 26, 2014
  • More »


Subscribe to this thread:

Add a comment

More by NUVO Editors

  • Best of Indy nominations open now

    Brand new this year? Completely open nominations. It's open season, Indianapolis. Nominate your favorite people, places and things now for our 2014 Best of Indy ballot.
    • Apr 25, 2014
  • Soften Our Hearts to Syria

    In facing a stalemated situation such as the Syrian Civil War, we know from the news that the various sides of the conflict have hardened their positions and won't compromise.
    • Apr 22, 2014
  • More »

Latest in News Blog

  • New life for Old City Hall
  • New life for Old City Hall

    Live Indy. Love Indy. Work Indy. Serve Indy. Connect Indy. It's all happening at Old City Hall.
    • Apr 9, 2014
  • NE Corridor Quality of Life Plan unveiling today
  • NE Corridor Quality of Life Plan unveiling today

    Nearly 27,000 people live in Northeast Corridor neighborhoods, which is bounded by 56th Street to the north, 16th Street to the south, Sherman Drive to the east and College Avenue to the west.
    • Mar 27, 2014
  • Indy's Sustainability Award Finalists Announced
  • Indy's Sustainability Award Finalists Announced

    Three finalists were selected for each of the Award's three categories: Economic, Environmental and Social.Three winners will be announced at the annual Indianapolis Sustainability Awards dinner on April 30.
    • Mar 26, 2014
  • More »

© 2014 NUVO | Website powered by Foundation