Nav: Home

Scientists simulate Earth's middle crust to understand earthquakes

September 28, 2015

Researchers have for the first time been able to measure a material's resistance to fracturing from various types of tectonic motions in the Earth's middle crust, a discovery that may lead to better understanding of how large earthquakes and slower moving events interact.

The University of Texas Institute for Geophysics (UTIG), research unit of the Jackson School of Geosciences, spearheaded the discovery. The study was published in the September edition of Nature Geoscience.

Scientists conducted the research using Carbopol, a gel-like substance that can simulate the characteristics of rock formations in the Earth's middle crust because it is simultaneously brittle and malleable.

Researchers performed shear tests on the Carbopol, where a portion of the material is pulled one direction and a portion is pulled in the opposite direction. This is similar to what happens to rock formations in the middle crust during earthquakes or slow-slip events, a type of tectonic movement that resembles an earthquake but happens over a much longer period of time.

Previously, nearly all research into such movements of the Earth's crusts was done by measuring tectonic movement using GPS readings and linking these findings with friction laws. Those observations did not address how rock behaves when it softens under heat and pressure.

"It is not really clear how slow-slip events interact with earthquakes, whether they can trigger earthquakes or it's the other way around - that earthquakes trigger slow-slip events," said Jacqueline Reber, the study's lead author who performed this research as postdoctoral fellow at UTIG, and who is now an assistant professor at Iowa State University.

The research also adds insight into middle crust strain transients, temporary stress on surrounding rock that's caused by tectonic motion.

"By understanding the mechanics of strain transients a little bit better, we eventually hope to get better insight into how they relate to big, catastrophic earthquakes."

Unlike slow slips events, earthquakes - or stick-slip events - occur when surfaces quickly alternate between sticking to each other and sliding over each other.

"While earlier studies focused mostly on frictional behavior as an explanation for strain transients we focus in our work on the impact of rheology (how a material flows under stress), especially when it is semi-brittle," said Reber.

The semi-brittle middle crust can be compared to a candy bar made of nuts and caramel. The nuts represent the brittle rock. The caramel represents the ductile rock.

Researchers exposed Carbopol, in which the ratio between brittle and ductile parts determines how much stress it can take before being permanently deformed or breaking, to forces created by a simple spring-powered shearing apparatus. Lower yield stress induced the Carbonol to imitate hotter, more viscous rock from deeper in the Earth's crust by making it more ductile; at higher yield stress it imitated cooler, more brittle rock.

The tests showed viscous deformation and constant creep movement at lower yield stress and slip-stick behavior at higher yield stress. This highlights the importance of a material's often complex properties for determining the manner and speed it will respond to stress.
-end-
The research team included Reber, Luc L. Lavier, an associate professor in the Jackson School's Department of Geological Sciences and a UTIG research scientist, and Nicholas W. Hayman, a UTIG research scientist.

Funding came from UTIG and Petrobras, a Brazilian energy corporation.

University of Texas at Austin

Related Stress Articles:

Stress in the powerhouse of the cell
University of Freiburg researchers discover a new principle -- how cells protect themselves from mitochondrial defects.
Measuring stress around cells
Tissues and organs in the human body are shaped through forces generated by cells, that push and pull, to ''sculpt'' biological structures.
Cellular stress at the movies
For the first time, biological imaging experts have used a custom fluorescence microscope and a novel antibody tagging tool to watch living cells undergoing stress.
Maternal stress at conception linked to children's stress response at age 11
A new study published in the Journal of Developmental Origins of Health and Disease finds that mothers' stress levels at the moment they conceive their children are linked to the way children respond to life challenges at age 11.
A new way to see stress -- using supercomputers
Supercomputer simulations show that at the atomic level, material stress doesn't behave symmetrically.
Beware of evening stress
Stressful events in the evening release less of the body's stress hormones than those that happen in the morning, suggesting possible vulnerability to stress in the evening.
How plants cope with stress
With climate change comes drought, and with drought comes higher salt concentrations in the soil.
Gene which decreases risk of social network-related stress, increases finance-related stress risk
Researchers have discovered that the same gene which increases your risk of depression following financial stress as you grow older also reduces your chance of depression associated with friendship and relationships stresses when young- your social network.
Innate stress
A team of researchers from the Higher School of Economics and the RAS Vavilov Institute of General Genetics has been able to statistically monitor the impact of the monoamine oxidase A gene (MAOA) on the subjective evaluation of well-being among men.
Is a stress shot on the horizon?
Rats immunized weekly for three weeks with beneficial bacteria showed increased levels of anti-inflammatory proteins in the brain, more resilience to the physical effects of stress, and less anxiety-like behavior.
More Stress News and Stress Current Events

Best Science Podcasts 2019

We have hand picked the best science podcasts for 2019. Sit back and enjoy new science podcasts updated daily from your favorite science news services and scientists.
Now Playing: TED Radio Hour

Rethinking Anger
Anger is universal and complex: it can be quiet, festering, justified, vengeful, and destructive. This hour, TED speakers explore the many sides of anger, why we need it, and who's allowed to feel it. Guests include psychologists Ryan Martin and Russell Kolts, writer Soraya Chemaly, former talk radio host Lisa Fritsch, and business professor Dan Moshavi.
Now Playing: Science for the People

#538 Nobels and Astrophysics
This week we start with this year's physics Nobel Prize awarded to Jim Peebles, Michel Mayor, and Didier Queloz and finish with a discussion of the Nobel Prizes as a way to award and highlight important science. Are they still relevant? When science breakthroughs are built on the backs of hundreds -- and sometimes thousands -- of people's hard work, how do you pick just three to highlight? Join host Rachelle Saunders and astrophysicist, author, and science communicator Ethan Siegel for their chat about astrophysics and Nobel Prizes.