Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

Columbia research examines mega earthquake threats

11.08.2003


New use for seismic reflection data: revealing the most dangerous fault lines on Earth



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.

Jill Stoddard | EurekAlert!
Further information:
http://www.ldeo.columbia.edu
http://www.earth.columbia.edu

More articles from Earth Sciences:

nachricht Strength of tectonic plates may explain shape of the Tibetan Plateau, study finds
25.07.2017 | University of Illinois at Urbana-Champaign

nachricht NASA flights gauge summer sea ice melt in the Arctic
25.07.2017 | NASA/Goddard Space Flight Center

All articles from Earth Sciences >>>

The most recent press releases about innovation >>>

Die letzten 5 Focus-News des innovations-reports im Überblick:

Im Focus: Carbon Nanotubes Turn Electrical Current into Light-emitting Quasi-particles

Strong light-matter coupling in these semiconducting tubes may hold the key to electrically pumped lasers

Light-matter quasi-particles can be generated electrically in semiconducting carbon nanotubes. Material scientists and physicists from Heidelberg University...

Im Focus: Flexible proximity sensor creates smart surfaces

Fraunhofer IPA has developed a proximity sensor made from silicone and carbon nanotubes (CNT) which detects objects and determines their position. The materials and printing process used mean that the sensor is extremely flexible, economical and can be used for large surfaces. Industry and research partners can use and further develop this innovation straight away.

At first glance, the proximity sensor appears to be nothing special: a thin, elastic layer of silicone onto which black square surfaces are printed, but these...

Im Focus: 3-D scanning with water

3-D shape acquisition using water displacement as the shape sensor for the reconstruction of complex objects

A global team of computer scientists and engineers have developed an innovative technique that more completely reconstructs challenging 3D objects. An ancient...

Im Focus: Manipulating Electron Spins Without Loss of Information

Physicists have developed a new technique that uses electrical voltages to control the electron spin on a chip. The newly-developed method provides protection from spin decay, meaning that the contained information can be maintained and transmitted over comparatively large distances, as has been demonstrated by a team from the University of Basel’s Department of Physics and the Swiss Nanoscience Institute. The results have been published in Physical Review X.

For several years, researchers have been trying to use the spin of an electron to store and transmit information. The spin of each electron is always coupled...

Im Focus: The proton precisely weighted

What is the mass of a proton? Scientists from Germany and Japan successfully did an important step towards the most exact knowledge of this fundamental constant. By means of precision measurements on a single proton, they could improve the precision by a factor of three and also correct the existing value.

To determine the mass of a single proton still more accurate – a group of physicists led by Klaus Blaum and Sven Sturm of the Max Planck Institute for Nuclear...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

Event News

Closing the Sustainability Circle: Protection of Food with Biobased Materials

21.07.2017 | Event News

»We are bringing Additive Manufacturing to SMEs«

19.07.2017 | Event News

The technology with a feel for feelings

12.07.2017 | Event News

 
Latest News

NASA mission surfs through waves in space to understand space weather

25.07.2017 | Physics and Astronomy

Strength of tectonic plates may explain shape of the Tibetan Plateau, study finds

25.07.2017 | Earth Sciences

The dense vessel network regulates formation of thrombocytes in the bone marrow

25.07.2017 | Life Sciences

VideoLinks
B2B-VideoLinks
More VideoLinks >>>