Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

Sediment layer may forecast greatest earthquakes

01.02.2006


Researchers at Yale and the University of Washington report that great earthquakes, like the 2004 Sumatra earthquake, may be caused by the build up of sediment on top of subduction zones, suggesting a new way to forecast these most severe earthquakes.



Subduction zones are the boundaries where two tectonic plates collide -- one plate pushes over and one pushes under the other. The most severe earthquakes in recent history -- in Indonesia in 2004, Alaska in 1964, Chile in 1960 and the Pacific Northwest in 1700 -- occurred at subduction zone faults. In the United States, there are subduction zones along the Aleutian margin of Alaska and the Cascadia margin bordering the west coast of the Pacific Northwest.

"Seismologists have long known that the motion of the plates at subduction zones can be smooth and steady in some areas, and sticky and unsteady in other areas," said Mark Brandon, professor of geology and geophysics at Yale and senior author on the paper appearing in the February issue of the journal Geology.


Earth plates move, and earthquakes ensue in these subduction zones, but some quakes are far more damaging than others. Doctoral student Christopher W. Fuller and associate professor Sean D. Willett at the University of Washington, along with Brandon at Yale, believe they have found a key to identifying specific areas within a subduction zone that will produce the most severe damage when they rupture.

The Earth’s surface is laced with about 32,000 miles of subduction zones, and the motion along the margins of the zones averages a slip of about two inches per year. However, where the margins stick and then rip apart into earthquakes, displacements have been as much as 65 feet, over many hundreds of miles, in a matter of only tens of minutes, according to Brandon.

The team used computer simulations to determine how the upper plate deformed above a subduction zone fault. "The leading edge of the overriding plate will continually deform, much like snow in front of a snow plow blade," according to Brandon. "As one plate moves under another and the upper plate deforms, it breaks up adhesion on the subduction fault and reduces its ability to generate greater earthquakes."

Past research has shown that as a subducting plate slides beneath an upper plate, stress builds where the plates meet and stick, and the upper plate warp creates a wedge and a bowl-shaped depression, called a forearc basin. Beneath the sea, this basin fills with sediment that empties from nearby rivers. It appears that the most severe subduction zone earthquakes occur in areas where such sediment-filled basins are found.

These current simulations showed, however, that when sediment was deposited on top of the overriding plate, it reinforced the edge of the plate and caused it to "stick," directly above where the earthquake would happen so that it no longer deformed internally. The researchers speculate that this allows the subduction zone to remain at rest for longer periods of time and thus to "stick," making it more prone to earthquake events.

"This phenomenon is analogous to a mayonnaise jar in the refrigerator. The lid opens easily if you use it every day. But if you open the jar infrequently, adhesion will make it difficult to open," said Brandon. "A sharp tap on a counter breaks the adhesion and the lid opens with a quick spin. In the Earth, the earthquake marks the break down of adhesion on the subduction zone."

"Over millions of years, the sediment typically piles to great depths, from a half-mile to nearly two miles, and in rare cases it might reach three miles deep," said Fuller, the lead author on the paper. "The increased weight of the sediment stops deformation from occurring."

This modeling could have implications for forecasting areas within a subduction zone, such as Cascadia, great earthquakes are the most likely to occur. But the work is not applicable to every subduction zone because each has different characteristics. "You have to understand the nature of basins and how they work in each area before you can use them as an interpretive tool," Fuller said.

Janet Rettig Emanuel | EurekAlert!
Further information:
http://www.yale.edu

More articles from Earth Sciences:

nachricht Climate change weakens Walker circulation
20.10.2017 | MARUM - Zentrum für Marine Umweltwissenschaften an der Universität Bremen

nachricht Shallow soils promote savannas in South America
20.10.2017 | Senckenberg Forschungsinstitut und Naturmuseen

All articles from Earth Sciences >>>

The most recent press releases about innovation >>>

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

Im Focus: Neutron star merger directly observed for the first time

University of Maryland researchers contribute to historic detection of gravitational waves and light created by event

On August 17, 2017, at 12:41:04 UTC, scientists made the first direct observation of a merger between two neutron stars--the dense, collapsed cores that remain...

Im Focus: Breaking: the first light from two neutron stars merging

Seven new papers describe the first-ever detection of light from a gravitational wave source. The event, caused by two neutron stars colliding and merging together, was dubbed GW170817 because it sent ripples through space-time that reached Earth on 2017 August 17. Around the world, hundreds of excited astronomers mobilized quickly and were able to observe the event using numerous telescopes, providing a wealth of new data.

Previous detections of gravitational waves have all involved the merger of two black holes, a feat that won the 2017 Nobel Prize in Physics earlier this month....

Im Focus: Smart sensors for efficient processes

Material defects in end products can quickly result in failures in many areas of industry, and have a massive impact on the safe use of their products. This is why, in the field of quality assurance, intelligent, nondestructive sensor systems play a key role. They allow testing components and parts in a rapid and cost-efficient manner without destroying the actual product or changing its surface. Experts from the Fraunhofer IZFP in Saarbrücken will be presenting two exhibits at the Blechexpo in Stuttgart from 7–10 November 2017 that allow fast, reliable, and automated characterization of materials and detection of defects (Hall 5, Booth 5306).

When quality testing uses time-consuming destructive test methods, it can result in enormous costs due to damaging or destroying the products. And given that...

Im Focus: Cold molecules on collision course

Using a new cooling technique MPQ scientists succeed at observing collisions in a dense beam of cold and slow dipolar molecules.

How do chemical reactions proceed at extremely low temperatures? The answer requires the investigation of molecular samples that are cold, dense, and slow at...

Im Focus: Shrinking the proton again!

Scientists from the Max Planck Institute of Quantum Optics, using high precision laser spectroscopy of atomic hydrogen, confirm the surprisingly small value of the proton radius determined from muonic hydrogen.

It was one of the breakthroughs of the year 2010: Laser spectroscopy of muonic hydrogen resulted in a value for the proton charge radius that was significantly...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

Event News

ASEAN Member States discuss the future role of renewable energy

17.10.2017 | Event News

World Health Summit 2017: International experts set the course for the future of Global Health

10.10.2017 | Event News

Climate Engineering Conference 2017 Opens in Berlin

10.10.2017 | Event News

 
Latest News

Terahertz spectroscopy goes nano

20.10.2017 | Information Technology

Strange but true: Turning a material upside down can sometimes make it softer

20.10.2017 | Materials Sciences

NRL clarifies valley polarization for electronic and optoelectronic technologies

20.10.2017 | Interdisciplinary Research

VideoLinks
B2B-VideoLinks
More VideoLinks >>>