Featured Research

from universities, journals, and other organizations

New Study Shows Earthquake Shaking Triggers Aftershocks

Date:
June 8, 2006
Source:
University of California - Santa Cruz
Summary:
A new analysis of earthquake data indicates that aftershocks are triggered by the shaking associated with the mainshock, rather than by the added stress on nearby faults resulting from rearrangement of the Earth's crust.

A new analysis of earthquake data indicates that aftershocks are triggered by the shaking associated with the mainshock, rather than by the added stress on nearby faults resulting from rearrangement of the Earth's crust.

Related Articles


The triggering of aftershocks by shaking may seem obvious, but is in fact a surprising result, said Emily Brodsky, assistant professor of Earth sciences at the University of California, Santa Cruz.

"The problem is that it's not clear how shaking can trigger an aftershock that doesn't happen right away, but happens a day or two after the earthquake. That's why most seismologists have thought that aftershocks are triggered by static stress resulting from the movement of the crust," Brodsky said.

Brodsky is coauthor of a paper describing the new findings in the June 8 issue of Nature. The first author of the paper is Karen Felzer, who began work on the study as a postdoctoral researcher with Brodsky at UCLA and is now with the U.S. Geological Survey in Pasadena.

Felzer and Brodsky looked at the distribution of aftershocks in relation to their distance from the site of the mainshock. They observed a smooth, consistent trend, with the number of aftershocks falling off steeply with increasing distance from the mainshock over a range from 0.2 to 50 kilometers (0.12 to 30 miles).

The smooth trend suggests that the same triggering process is operating over the entire distance range. But static stress is negligible at the far end of the range, so the dynamic stress from shaking must be the trigger, Felzer said.

"No one expected small earthquakes to trigger aftershocks at these distances," she said. "The traditional idea is that the aftershock zone is one to two times the length of the fault rupture, so for earthquakes of this size you wouldn't expect to see aftershocks beyond more than one kilometer. We're seeing aftershocks all the way out to 50 kilometers."

Furthermore, the aftershocks fall off in the same relation to distance as is seen in the decay of seismic waves. In other words, the number of aftershocks and the amount of shaking show the same mathematical relation to distance from the mainshock (an "inverse power law" relation).

"That's the kicker. The aftershocks fall off with distance in the same way that seismic waves do," Brodsky said. "We propose that the chance of having an aftershock depends directly on the amplitude of the shaking."

This hypothesis is consistent not only with the researchers' measurements of how aftershock density varies with distance, but also with previous measurements of the number of aftershocks triggered by a mainshock of a particular magnitude, Brodsky said.

The data analyzed in this study were obtained from a large catalog of southern California earthquakes with precise earthquake locations, published in 2005. This research was supported in part by a grant from the National Science Foundation.


Story Source:

The above story is based on materials provided by University of California - Santa Cruz. Note: Materials may be edited for content and length.


Cite This Page:

University of California - Santa Cruz. "New Study Shows Earthquake Shaking Triggers Aftershocks." ScienceDaily. ScienceDaily, 8 June 2006. <www.sciencedaily.com/releases/2006/06/060608091307.htm>.
University of California - Santa Cruz. (2006, June 8). New Study Shows Earthquake Shaking Triggers Aftershocks. ScienceDaily. Retrieved November 25, 2014 from www.sciencedaily.com/releases/2006/06/060608091307.htm
University of California - Santa Cruz. "New Study Shows Earthquake Shaking Triggers Aftershocks." ScienceDaily. www.sciencedaily.com/releases/2006/06/060608091307.htm (accessed November 25, 2014).

Share This


More From ScienceDaily



More Earth & Climate News

Tuesday, November 25, 2014

Featured Research

from universities, journals, and other organizations


Featured Videos

from AP, Reuters, AFP, and other news services

Antarctic Sea Ice Mystery Thickens... Literally

Antarctic Sea Ice Mystery Thickens... Literally

Newsy (Nov. 25, 2014) — Antarctic sea ice isn't only expanding, it's thicker than previously thought, and scientists aren't sure exactly why. Video provided by Newsy
Powered by NewsLook.com
3D Map of Antarctic Sea Ice to Shed Light on Climate Change

3D Map of Antarctic Sea Ice to Shed Light on Climate Change

Reuters - Innovations Video Online (Nov. 24, 2014) — A multinational group of scientists have released the first ever detailed, high-resolution 3-D maps of Antarctic sea ice. Using an underwater robot equipped with sonar, the researchers mapped the underside of a massive area of sea ice to gauge the impact of climate change. Ben Gruber reports. Video provided by Reuters
Powered by NewsLook.com
Car Park Solution for Flexible Green Energy

Car Park Solution for Flexible Green Energy

Reuters - Innovations Video Online (Nov. 24, 2014) — A British solar power start-up says that by covering millions of existing car park spaces around the UK with flexible solar panels, the country's power problems could be solved. Suzannah Butcher reports. Video provided by Reuters
Powered by NewsLook.com
Yellow-Spotted Turtles Rescued from Trafficking

Yellow-Spotted Turtles Rescued from Trafficking

Reuters - Light News Video Online (Nov. 24, 2014) — Hundreds of Amazon River turtles released into the wild in Peru. Sharon Reich reports. Video provided by Reuters
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:

Strange & Offbeat Stories

 

Plants & Animals

Earth & Climate

Fossils & Ruins

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