Featured Research

from universities, journals, and other organizations

Columbia Research Examines Mega Earthquake Threats

Date:
August 11, 2003
Source:
The Earth Institute At Columbia University
Summary:
Researchers have found an important new application for seismic reflection data, commonly used to image geological structures and explore for oil and gas. Recently published in the journal Nature, new use of reflection data may prove crucial to understanding the potential for mega earthquakes.

Researchers have found an important new application for seismic reflection data, commonly used to image geological structures and explore for oil and gas. Recently published in the journal Nature, new use of reflection data may prove crucial to understanding the potential for mega earthquakes.

Mladen Nedimovic, the lead author and a scientist at the Lamont-Doherty Earth Observatory, a member of the Earth Institute at Columbia University, examined reflection data collected on the northern Cascadia margin off the coast of Vancouver Island. Cascadia margin is an area where the north Pacific seafloor is being pushed under the continental margin of North America. Locations where oceanic plates are underthrusting the continents are known as subduction zones. Within subduction zones are enormous faults called megathrusts, the places where the two tectonic plates meet and interface one another. Megathrusts are the source of the largest and most devastating earthquakes on Earth.

From the reflection data, Nedimovic and his coauthors mapped the locked zone on the megathrust along the northern Cascadia margin, which hosts the populous cities of Vancouver and Seattle. Locked zones, where geological structures beneath the surface are tightly interfaced, build up enormous pressure as the Earth shifts. In 1700, the pressure beneath the Cascadia margin was released, resulting in a magnitude 9 earthquake that devastated the region. A magnitude 9 earthquake releases over 1000 times more energy than was released during the magnitude 6.8 Nisqually earthquake that shook Seattle two years ago.

Currently, dislocation and thermal modeling are used for mapping locked zones, however, both methods rely on many assumptions about Earth's structure that may limit their accuracy. In fact, for the northern Cascadia margin, estimates of the locked zone using these techniques indicate that a 36-mile (~60 km) swath of land from the subduction trench toward Vancouver Island is locked. Nedimovic's reflection analysis shows that it is more likely to be a 56-mile (~90 km) swath, extending the zone some 20 miles (~30 km) closer to land. If this is accurate, rapidly growing inland cities face a greater threat from megathrust earthquake hazards than previously anticipated. The occurrence rate for great earthquakes on the Cascadia megathrust is approximately every 200 to 800 years. We are currently within the timeframe where another large earthquake is expected, with the last earthquake having occurred over 300 years ago.

Seismic and aseismic slip occurs on different parts of a megathrust, at different depths, temperatures, and pressures, and due to different types of rock deformation. Brittle rock failure affects a narrow zone around the thrust where seismic slip is observed, and plastic deformation affects a much wider area above the thrust where the slip is slow and aseismic. Seismic reflection imaging reveals the variations in structures along the megathrust and can be used for detailed mapping of locked and slow-slipping zones.

"Deep seismic reflection images from Alaska, Chile, and Japan show a similar broad reflection band above the megathrust in the region of stable sliding and thin thrust reflections further seaward where the megathrust is locked, suggesting that reflection imaging may be a globally important predictive tool for determining the maximum expected rupture area in great subduction earthquakes," said Nedimovic. " Mega earthquakes have been instrumentally recorded for all three regions making them potential targets for a future investigation to confirm the reflection method and improve characterization of megathrust seismic hazards in the study area."

The northern Cascadia margin study was funded by the National Earthquake Hazards Reduction Program of the United States Geological Survey and by the Geological Survey of Canada. Mladen Nedimovic and his collaborators are submitting a proposal to National Science Foundation to carry out a megathrust seismic hazards characterization study along the southern Alaska margin.

###

KEY

Subduction zone--the zone of convergence of two tectonic plates, one of which overrides the other

Megathrust--where two tectonic plates in a subduction zone meet and interface with one another

Locked zone--part of the subduction thrust where geological structures beneath the surface are tightly interfaced and rupture in large to great earthquakes

###

The Lamont-Doherty Earth Observatory, a member of The Earth Institute at Columbia University, is one of the world's leading research centers examining the planet from its core to its atmosphere, across every continent and every ocean. From global climate change to earthquakes, volcanoes, environmental hazards and beyond, Observatory scientists provide the basic knowledge of Earth systems needed to inform the future health and habitability of our planet. For more information, visit www.ldeo.columbia.edu.

The Earth Institute at Columbia University is the world's pioneer academic center for mobilizing the sciences and public policy in pursuit of a sustainable future, especially for the world's poor. Its director is international economist Jeffrey D. Sachs. More than 800 scientists with strength in Earth science, ecology, health, social science or engineering are working together to reduce poverty, hunger, disease and environmental degradation. The Institute brings their creative knowledge to bear through teaching, research and outreach in dozens of countries around the world. In all it does, the Earth Institute remains mindful of the staggering disparities between rich and poor nations and the tremendous impact that global-scale problems – from the AIDS pandemic to climate change to extreme poverty in much of the developing world – will have on all nations. For more information, visit http://www.earth.columbia.edu.


Story Source:

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


Cite This Page:

The Earth Institute At Columbia University. "Columbia Research Examines Mega Earthquake Threats." ScienceDaily. ScienceDaily, 11 August 2003. <www.sciencedaily.com/releases/2003/08/030811065935.htm>.
The Earth Institute At Columbia University. (2003, August 11). Columbia Research Examines Mega Earthquake Threats. ScienceDaily. Retrieved April 20, 2014 from www.sciencedaily.com/releases/2003/08/030811065935.htm
The Earth Institute At Columbia University. "Columbia Research Examines Mega Earthquake Threats." ScienceDaily. www.sciencedaily.com/releases/2003/08/030811065935.htm (accessed April 20, 2014).

Share This



More Earth & Climate News

Sunday, April 20, 2014

Featured Research

from universities, journals, and other organizations


Featured Videos

from AP, Reuters, AFP, and other news services

Drought Concerns May Hurt Lake Tourism

Drought Concerns May Hurt Lake Tourism

AP (Apr. 18, 2014) Operators of recreational businesses on western reservoirs worry that ongoing drought concerns will keep boaters and other visitors from flocking to the popular summer attractions. (April 18) Video provided by AP
Powered by NewsLook.com
Man Claims He Found Loch Ness Monster With... Apple Maps?

Man Claims He Found Loch Ness Monster With... Apple Maps?

Newsy (Apr. 18, 2014) Andy Dixon showed the Daily Mail a screenshot of what he believes to be the mythical beast swimming just below the lake's surface. Video provided by Newsy
Powered by NewsLook.com
First Ever 'Female Penis' Discovered In Animal Kingdom

First Ever 'Female Penis' Discovered In Animal Kingdom

Newsy (Apr. 18, 2014) Not only are these newly discovered bugs' sex organs reversed, but they also mate for up to 70 hours. Video provided by Newsy
Powered by NewsLook.com
Ark. Man Finds 6-Carat Diamond At State Park

Ark. Man Finds 6-Carat Diamond At State Park

Newsy (Apr. 18, 2014) An Arkansas man has found a nearly 6.2-carat diamond, which he dubbed "The Limitless Diamond," at the Crater of Diamonds State Park. 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