Featured Research

from universities, journals, and other organizations

New Method Of Dating Past Earthquakes, Assessing Future Ones Discovered

Date:
January 13, 1999
Source:
Vanderbilt University
Summary:
A Vanderbilt University researcher has unearthed a new way of dating earthquakes, providing a more precise timeline for past quakes and allowing for a more accurate way of assessing the probability of future quakes. Jay S. Noller, assistant professor of geology, made the discoveries while studying the Hebgen Lake fault in Montana.

NASHVILLE, Tenn. -- A Vanderbilt University researcher has unearthed a new way of dating earthquakes, providing a more precise timeline for past quakes and allowing for a more accurate way of assessing the probability of future quakes. Jay S. Noller, assistant professor of geology, made the discoveries while studying the Hebgen Lake fault in Montana. His research was featured in the Nov. 6 issue of the journal Science.

Noller and his research partner Marek Zreda of the University of Arizona discovered while studying bedrock formations that the chemical makeup of the bedrock had changed after it was affected by an earthquake. By taking a closer look at the bedrock, they were able to determine how long ago the quake had occurred, how often quakes occur in that area, and the probability of another quake happening.

Earthquake dating and predicting is currently done by studying events that occurred either before or after an earthquake -- for example, by looking at rivers that crossed over a fault line. Noller's method looks at what occurred at the very moment an earthquake hit.

"That's what's revolutionary about this," Noller said. "This opens up a new range of potential study sites. Bedrock exposures last tens of thousands of years, but river deposits don't last as long -- they get buried or eroded away, so they last only a few thousand years. The longer the track record you have of an area, the better idea you have of how things work. The track record lets us estimate the likelihood of future earthquakes."

Most of the faults that run through the United States are in bedrock, such as the New Madrid fault in West Tennessee and faults near New York City. Because there are more bedrock faults and fewer river deposits than in the West, it has been very difficult to assess past, and hence future, seismic action in that area.

"There are some bedrock faults in New Jersey and New York that have bothered geologists for a long time now. They've looked at them and said, 'We don't know how to date when the last time this fault moved,' because there are no river deposits there."

Noller's research is funded by the U. S. Nuclear Regulatory Commission, with the express purpose of better assessing the activity of faults around the nation's nuclear facilities, which are primarily located in the eastern United States - which is where most bedrock faults are located. Noller's research now provides a tool with which to find answers to how seismically safe the nuclear facilities are, as well as how safe the major metropolitan areas in the East are.

This is how Noller's research works: after a large-magnitude earthquake occurs, the earth's crust is shifted, exposing parts of the earth that had previously never seen daylight. These rocks contain elements such as potassium and calcium, which become chlorine after exposure to cosmic rays. In particular, Noller looks for the isotope 36Cl, which although found in nature, occurs in very small amounts in most rocks. But because of the bedrock's exposure to cosmic rays, 36Cl is found in high numbers in seismically altered bedrock.

After thousands of years and many quakes, more and more of the earth is exposed, creating bands of different colors that Noller describes as looking like "a big piece of bacon," the bands near the top being the oldest. Noller takes samples of the rock and counts the number of atoms of 36Cl found -- the longer a piece of rock has been exposed to cosmic rays, the more 36Cl is present.

"You can see exactly how much of the earth moved during these earthquakes," Noller said. "The exposure of rock is directly proportional to the size of the earthquake. It's very clear and plain to see - it's elegant and simple and it tells us the exact time it happened."

The Hebgen Lake fault was chosen as Noller's base of research because it was the site of a catastrophic 7.5 magnitude earthquake in 1959. During that quake, the ground was raised 21 feet -- "the largest amount of displacement ever recorded anywhere on the globe."

Noller also discovered while investigating the Hebgen Lake fault that when the 1959 quake occurred, it had an effect on the geysers in nearby areas. Old Faithful in Yellowstone National Park slowed down, new geysers were formed and old ones stopped. "It's interesting to see how it affected the natural history of that area," he said. "This record of earthquakes should shed light on the history of changes in the geyser fields."


Story Source:

The above story is based on materials provided by Vanderbilt University. Note: Materials may be edited for content and length.


Cite This Page:

Vanderbilt University. "New Method Of Dating Past Earthquakes, Assessing Future Ones Discovered." ScienceDaily. ScienceDaily, 13 January 1999. <www.sciencedaily.com/releases/1999/01/990113080413.htm>.
Vanderbilt University. (1999, January 13). New Method Of Dating Past Earthquakes, Assessing Future Ones Discovered. ScienceDaily. Retrieved September 16, 2014 from www.sciencedaily.com/releases/1999/01/990113080413.htm
Vanderbilt University. "New Method Of Dating Past Earthquakes, Assessing Future Ones Discovered." ScienceDaily. www.sciencedaily.com/releases/1999/01/990113080413.htm (accessed September 16, 2014).

Share This



More Earth & Climate News

Tuesday, September 16, 2014

Featured Research

from universities, journals, and other organizations


Featured Videos

from AP, Reuters, AFP, and other news services

Raw: Scientists Examine Colossal Squid

Raw: Scientists Examine Colossal Squid

AP (Sep. 16, 2014) Squid experts in New Zealand thawed and examined an unusual catch on Tuesday: a colossal squid. It was captured in Antarctica's remote Ross Sea in December last year and has been frozen for eight months. (Sept. 16) Video provided by AP
Powered by NewsLook.com
Man Floats for 31 Hours in Gulf Waters

Man Floats for 31 Hours in Gulf Waters

AP (Sep. 16, 2014) A Texas man is lucky to be alive after he and three others floated for more than a day in the Gulf of Mexico when their boat sank during a fishing trip. (Sept. 16) Video provided by AP
Powered by NewsLook.com
Researchers Explore Shipwrecks Off Calif. Coast

Researchers Explore Shipwrecks Off Calif. Coast

AP (Sep. 16, 2014) Federal researchers are exploring more than a dozen underwater sites where they believe ships sank in the treacherous waters west of San Francisco in the decades following the Gold Rush. (Sept. 16) Video provided by AP
Powered by NewsLook.com
Conservationists Face Uphill PR Battle With New Shark Rules

Conservationists Face Uphill PR Battle With New Shark Rules

Newsy (Sep. 14, 2014) New conservation measures for shark fishing face an uphill PR battle in the fight to slow shark extinction. Video provided by Newsy
Powered by NewsLook.com

Search ScienceDaily

Number of stories in archives: 140,361

Find with keyword(s):
Enter a keyword or phrase to search ScienceDaily for related topics and research stories.

Save/Print:
Share:

Breaking News:
from the past week

In Other News

... from NewsDaily.com

Science News

Health News

    Environment News

      Technology News



      Save/Print:
      Share:

      Free Subscriptions


      Get the latest science news with ScienceDaily's free email newsletters, updated daily and weekly. Or view hourly updated newsfeeds in your RSS reader:

      Get Social & Mobile


      Keep up to date with the latest news from ScienceDaily via social networks and mobile apps:

      Have Feedback?


      Tell us what you think of ScienceDaily -- we welcome both positive and negative comments. Have any problems using the site? Questions?
      Mobile: iPhone Android Web
      Follow: Facebook Twitter Google+
      Subscribe: RSS Feeds Email Newsletters
      Latest Headlines Health & Medicine Mind & Brain Space & Time Matter & Energy Computers & Math Plants & Animals Earth & Climate Fossils & Ruins