Printer Friendly

Estimating a temblor's strength on the fly.

New analyses of ground motions caused by large earthquakes suggest that it may be possible to estimate the full magnitude of such quakes immediately after they start rumbling. That could enable emergency systems to better warn distant populations of a temblor before it reaches them.

Currently, it isn't possible to measure an earthquake's total magnitude until the rumbling has stopped. That's because the seismic energy that's released depends on the total slippage that occurs between two sides of a fault, says Richard M. Allen, a seismologist at the University of California, Berkeley.

He and his colleagues have discovered a quick way to estimate a quake's magnitude if there happens to be a seismometer near its epicenter.

A seismometer within 100 kilometers of the epicenter records both high- and low-frequency vibrations, whereas instruments farther away receive only low frequencies. Alter studying ground-motion patterns of 71 quakes recorded by nearby seismometers, Alien and his colleagues noticed that the relative amounts of energy going into the two vibration categories varied systematically with the size of the quake.

Although fault slippage in most small quakes included in the study lasted only a second or so, several of the large quakes rumbled for more than 30 seconds. Nevertheless, the researchers found that the ratio of seismic energy received at high and low frequencies during the first 4 seconds of ground motions spreading from the quake enabled the team to estimate the quake's full magnitude.

The technique may make it possible for scientists to more quickly recognize that an ongoing earthquake will be large and damaging, says Allen. He and his colleagues report their findings in the Nov. 10, 2005 Nature.--S.P.
COPYRIGHT 2006 Science Service, Inc.
No portion of this article can be reproduced without the express written permission from the copyright holder.
Copyright 2006, Gale Group. All rights reserved. Gale Group is a Thomson Corporation Company.

Article Details
Printer friendly Cite/link Email Feedback
Title Annotation:seismological research
Publication:Science News
Article Type:Brief Article
Geographic Code:1USA
Date:Jan 7, 2006
Words:277
Previous Article:Protein exposes long-term risk from heart problems.
Next Article:Facing a hairy electronics problem.
Topics:


Related Articles
'Preshock' pattern may foretell quakes.
Cracking open the center of a temblor.
Ripples spread wide from ground zero.
Finding fault for an old earthquake. (Earth Science).
TURKEY - Feb. 3 - Earthquake In ?entral Anatolia.
BRIEFLY QUAKES SHAKE SOUTHLAND.
In case of temblor, run downhill. (Seismology).
SMALL QUAKE RATTLES AREA; NO DAMAGES.
Rome at risk: seismic shaking could be long and destructive.
Region at risk: a look at San Francisco's seismic past and future.

Terms of use | Privacy policy | Copyright © 2019 Farlex, Inc. | Feedback | For webmasters