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 Giant see-saw of monsoon rains detected
26.09.2016 | Potsdam-Institut für Klimafolgenforschung

nachricht A new 3D viewer for improved digital geoscience mapping
20.09.2016 | Uni Research

All articles from Earth Sciences >>>

The most recent press releases about innovation >>>

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

Im Focus: First quantum photonic circuit with electrically driven light source

Optical quantum computers can revolutionize computer technology. A team of researchers led by scientists from Münster University and KIT now succeeded in putting a quantum optical experimental set-up onto a chip. In doing so, they have met one of the requirements for making it possible to use photonic circuits for optical quantum computers.

Optical quantum computers are what people are pinning their hopes on for tomorrow’s computer technology – whether for tap-proof data encryption, ultrafast...

Im Focus: OLED microdisplays in data glasses for improved human-machine interaction

The Fraunhofer Institute for Organic Electronics, Electron Beam and Plasma Technology FEP has been developing various applications for OLED microdisplays based on organic semiconductors. By integrating the capabilities of an image sensor directly into the microdisplay, eye movements can be recorded by the smart glasses and utilized for guidance and control functions, as one example. The new design will be debuted at Augmented World Expo Europe (AWE) in Berlin at Booth B25, October 18th – 19th.

“Augmented-reality” and “wearables” have become terms we encounter almost daily. Both can make daily life a little simpler and provide valuable assistance for...

Im Focus: Artificial Intelligence Helps in the Discovery of New Materials

With the help of artificial intelligence, chemists from the University of Basel in Switzerland have computed the characteristics of about two million crystals made up of four chemical elements. The researchers were able to identify 90 previously unknown thermodynamically stable crystals that can be regarded as new materials. They report on their findings in the scientific journal Physical Review Letters.

Elpasolite is a glassy, transparent, shiny and soft mineral with a cubic crystal structure. First discovered in El Paso County (Colorado, USA), it can also be...

Im Focus: Complex hardmetal tools out of the 3D printer

For the first time, Fraunhofer IKTS shows additively manufactured hardmetal tools at WorldPM 2016 in Hamburg. Mechanical, chemical as well as a high heat resistance and extreme hardness are required from tools that are used in mechanical and automotive engineering or in plastics and building materials industry. Researchers at the Fraunhofer Institute for Ceramic Technologies and Systems IKTS in Dresden managed the production of complex hardmetal tools via 3D printing in a quality that are in no way inferior to conventionally produced high-performance tools.

Fraunhofer IKTS counts decades of proven expertise in the development of hardmetals. To date, reliable cutting, drilling, pressing and stamping tools made of...

Im Focus: Launch of New Industry Working Group for Process Control in Laser Material Processing

At AKL’16, the International Laser Technology Congress held in May this year, interest in the topic of process control was greater than expected. Appropriately, the event was also used to launch the Industry Working Group for Process Control in Laser Material Processing. The group provides a forum for representatives from industry and research to initiate pre-competitive projects and discuss issues such as standards, potential cost savings and feasibility.

In the age of industry 4.0, laser technology is firmly established within manufacturing. A wide variety of laser techniques – from USP ablation and additive...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

Event News

Laser use for neurosurgery and biofabrication - LaserForum 2016 focuses on medical technology

27.09.2016 | Event News

Experts from industry and academia discuss the future mobile telecommunications standard 5G

23.09.2016 | Event News

ICPE in Graz for the seventh time

20.09.2016 | Event News

 
Latest News

New switch decides between genome repair and death of cells

27.09.2016 | Life Sciences

Nanotechnology for energy materials: Electrodes like leaf veins

27.09.2016 | Physics and Astronomy

‘Missing link’ found in the development of bioelectronic medicines

27.09.2016 | Life Sciences

VideoLinks
B2B-VideoLinks
More VideoLinks >>>