Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

Melting rock - Researchers unlocked the secrets of "deep" earthquakes

03.02.2009
How do earthquakes occur at great depths?

This is the question being answered by scientists working with Dr. Timm John from the Institute of Mineralogy at the University of Münster, using an innovative combination of field and laboratory work with numerical computer simulations.

The researchers from Münster, Kiel and Oslo (Norway) present their results in the latest issue of the prestigious magazine Nature Geoscience.

The margins of the Earth's tectonic plates are characterized by a very high level of earthquake activity, which can originate at depths of just a few - or of several hundred - kilometres.

At places where converging plates override each another at their margins, earthquakes often occur at depths of more than 50 kilometres below the Earth's surface. "The mechanisms of 'shallow' earthquakes which occur at a depth of up to 50 kilometres are very well known," says John, "and they are attributable to failure in the tectonic plates displaying brittle behaviour. However, the causes of deeper earthquakes are still unclear today." As a rule, the behaviour of rocks under conditions at greater depth is ductile and not brittle. Conventional wisdom, however, says that here too brittle-like failure in the rock plays a role in connection with earthquakes.

During fieldwork in western Norway John and his colleagues from the Center for Physics of Geological Processes at the University of Oslo found shear zones in the rock they examined which are attributable to ductile deformation. In addition, there were earthquake fault zones present which the current state of research would interpret as brittle failure structures, but which, according to the scientists' latest insights, have other causes: "Our examinations showed that deeper earthquakes can in many cases be explained by shear heating of the rock," says John.

In such a case, the heating process which comes into being as a result of an initially very slow deformation of the rock along evolving shear zones leads to the rock becoming increasingly weaker and thus more deformable. In turn, this increasing deformation causes it to heat up. This process, which is self-amplifying, ultimately leads to the rock along a very thin zone becoming so hot that it begins to melt. The entire pent-up stress can then be released at seismic speed on this melted rock. The result is an earthquake.

"The simulations, which took into account the data gained in the field and in the laboratory, also showed," says John, "that the shear zones and the earthquake fault zones were formed by the same process. Very small differences in the rock properties decide whether a shear zone is formed or the deformation structure actually develops into an earthquake fault zone."

Dr. Christina Heimken | idw
Further information:
http://www.uni-muenster.de/Mineralogie/personen/john.html
http://www.nature.com/ngeo/journal/v2/n2/abs/ngeo419.html

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

NRL clarifies valley polarization for electronic and optoelectronic technologies

20.10.2017 | Interdisciplinary Research

Metallic nanoparticles will help to determine the percentage of volatile compounds

20.10.2017 | Materials Sciences

Shallow soils promote savannas in South America

20.10.2017 | Earth Sciences

VideoLinks
B2B-VideoLinks
More VideoLinks >>>