(Press-News.org) Earthquake damage to buildings is mainly due to the existing shear waves which transfer their energy during an earthquake to the houses. These shear waves are significantly influenced by the underground and the topography of the surrounding area. Detailed knowledge of the landform and the near-surface underground structure is, therefore, an important prerequisite for a local seismic hazard assessment and for the evaluation of the ground-effect, which can strongly modify and increase local ground motion.
As described in the latest issue of Geophysical Journal International, a team of scientists from the GFZ German Research Center for Geosciences could show that it is possible to map complex shear wave velocity structures almost in real time by means of a newly developed tomgraphic approach.
The method is based on ambient seismic noise recordings and analyses. "We use small, hardly noticeable amplitude ground motions as well as anthropogenic ground vibrations", Marco Pilz, a scientist at GFZ, explains. "With the help of these small signals we can obtain detailed images of the shallow seismic velocity structure". In particular, images and velocity changes in the underground due to earthquakes and landslides can be obtained in almost real time.
"What is new about our method is the direct calculation of the shear wave velocity. Moreover, we are working on a local, small-scale level -- compared to many other studies", Marco Pilz continues.
This method has already been successfully applied: Many regions of Central Asia are threatened by landslides. Since the shear wave velocity usually drops significantly before a landslide slip this technique offers the chance to monitor changes in landslide prone areas almost in real time.
Further application can be used in earthquake research. The authors were able to map the detailed structure of a section of the Issyk-Ata fault, Kyrgyzstan, which runs along the southern border of the capital city, Bishkek, with a population of approx. 900.000 inhabitants. They showed that close to the surface of the mapped section a splitting into two different small fault branches can be observed. This can influence the pace of expansion or also an eventual halting of the propagation on the main fault.
Central Asia is extensively seismically endangered; the accompanying processes and risks are investigated by the Central-Asian Institute of Applied Geosciences (CAIAG) in Bishkek, a joint institution established by the GFZ and the Kyrgyz government.
Why do these earthquakes occur?
The Pamir and Tien Shan are the result of the crash of two continental plates: the collision of India and Eurasia causes the high mountain ranges. This process is still ongoing today and causes breaking of the Earths crust, of which earthquakes are the consequence.
A second group of GFZ-scientists has investigated together with colleagues from Tajikistan and CAIAG the tectonic process of collision in this region. They were, for the first time, able to image continental crust descending into the Earth's mantle. In the scientific journal Earth and Planetary Sciences Letters the scientists report that this subduction of continental crust has, to date, never been directly observed. To make their images, the scientists applied a special seismological method (so-called receiver function-analysis) on seismograms that had been collected in a two years long field experiment in the Tien Shan-Pamir-Hindu Kush area. Here, the collision of the Indian and Eurasian plates presents an extreme dimension.
"These extreme conditions cause the Eurasian lower crust to subduct into the Earth's mantle", explains Felix Schneider from the GFZ German Research Centre for Geosciences." Such a subduction can normally be observed during the collision of ocean crust with continental crust, as the ocean floors are heavier than continental rock."
Findings at the surface of metamorphic rocks that must have arisen from ultra-high pressures deep in the Earth's mantle also provide evidence for subduction of continental crust in the Pamir region. Furthermore, the question arises, how the occurrence of numerous earthquakes at unusual depths of down to 300 km in the upper mantel can be explained. Through the observation of the subducting part of the Eurasian lower crust, this puzzle could, however, be solved.
###
M. Pilz, S. Parolai, D. Bindi, "Three-dimensional passive imaging of complex seismic fault systems: evidence of surface traces of the Issyk-Ata fault (Kyrgyzstan)", Geophysical Journal International, September 2013, 194(3), 1955-1965, doi:10.1093/gji/ggt214
Schneider, F. M.; Yuan, X.; Schurr, B.; Mechie, J.; Sippl, C.; Haberland, C.;
Minaev, V.; Oimahmadov, I.; Gadoev, M.; Radjabov, N.; Abdybachaev, U.;
Orunbaev, S.; Negmatullaev, S. (2013): "Seismic imaging of subducting continental lower crust beneath the Pamir", Earth and Planetary Science Letters, Volume 375, August 2013, S. 101-112, doi: 10.1016/j.epsl.2013.05.015
Pictures in printable resolution can be found here:
http://www.gfz-potsdam.de/portal/gfz/Public+Relations/Ressourcen-Images/130826_Hangrutsch
http://www.gfz-potsdam.de/portal/gfz/Public+Relations/Ressourcen-Images/130826_Subduktion_Pamir
Earthquakes and tectonics in Pamir Tien Shan
Real time observation of shear waves on the Earth's surface, first direct observation of subducting continental crust during the collision of two continents
2013-08-27
ELSE PRESS RELEASES FROM THIS DATE:
Computer test reveals high prevalence of attention disorders in stroke patients
2013-08-27
A majority of stroke patients have problems paying attention and could be helped by brain-training computer games, a new study suggests.
Researchers at Imperial College London found that problems such as difficulty filtering out distractions, difficulty following instructions, and reduced alertness are much more common in stroke patients than doctors realise.
Their study, published in Neurology, showed that brain scans and bedside tests can be used to diagnose these three types of attention problems, each of which could be addressed with computer games tailored for the ...
Existence of new element confirmed
2013-08-27
An international team of researchers, led by physicists from Lund University, have confirmed the existence of what is considered a new element with atomic number 115. The experiment was conducted at the GSI research facility in Germany. The results confirm earlier measurements performed by research groups in Russia.
"This was a very successful experiment and is one of the most important in the field in recent years", said Dirk Rudolph, Professor at the Division of Atomic Physics at Lund University.
Besides the observations of the new chemical element, the researchers ...
New energy model offers transparency to let others replicate findings
2013-08-27
Computer models are used to inform policy decisions about energy, but existing models are generally "black boxes" that don't show how they work, making it impossible for anyone to replicate their findings. Researchers from North Carolina State University have developed a new open-source model and are sharing the data they put into it, to allow anyone to check their work – an important advance given the environmental and economic impact of energy policy decisions.
"Most models show you the math behind how they work, but don't share the source code that is supposed to implement ...
An alga stressed by the light
2013-08-27
This news release is available in Spanish.
Gelidium corneum is a very common alga along the Basque coast. It grows at a depth of between 3 and 15 metres, and from September onwards can be seen out of the water. It gets broken up by storms and washed up on the beaches where it forms a red carpet. On some parts of the coast, above all in transparent water zones, the fronds of the algae have turned yellowish. The researchers have identified this change as a symptom of stress.
There are more sunny days during the summer which is when the algae are exposed to increased ...
Dating violence impedes victims' earnings
2013-08-27
EAST LANSING, Mich. — Dating violence in adolescence not only takes a physical and emotional toll on young women, it also leads to less education and lower earnings later in life, according to a first-of-its-kind study led by a Michigan State University researcher.
A young woman's educational performance may be hindered by her partner's actions, such as destroying books or homework or causing injuries that prevent her from going to school.
The findings, reported in the Journal of Interpersonal Violence, reinforce the need for programs and efforts to support victims' ...
Can toxicity of a DNA drug be predicted and minimized?
2013-08-27
New Rochelle, NY, August 26, 2013—New classes of therapeutic antisense oligonucleotides can have toxic effects on the liver. A novel machine learning-based approach used to predict the hepatotoxic potential of an antisense drug based on its chemical sequence is presented in Nucleic Acid Therapeutics, a peer-reviewed journal from Mary Ann Liebert, Inc. publishers. The article is available on the Nucleic Acid Therapeutics website.
Peter Hagedorn and coauthors from Santaris Pharma, Hørsholm, Denmark, and University of Copenhagen, Denmark, describe the use of machine learning ...
Anchoring ABL for a better fate
2013-08-27
Chronic Myelogenous Leukemia (CML) is a cancer of the white blood cells that is most commonly found in adults and in the elderly. Its incidence has been estimated to be 1 to 2 in 100,000 people. CML was the first cancer to be associated with a genetic abnormality, known as the Philadelphia Chromosome, which 95% of all CML patients carry in their cells.
The Philadelphia Chromosome is formed by exchanges of material belonging to two distinct chromosomes, number 9 and number 22. To form the Philadelphia Chromosome, these two chromosomes break at very specific places, disrupting ...
Tennessee high school students publish in top science journal
2013-08-27
KNOXVILLE—Two Tennessee high school students have now done what many scientists strive for: publishing their research in a top science journal.
Dalton Chaffee and Hayes Griffin worked with mentor R. Tucker Gilman, a former postdoctoral research fellow at the National Institute for Mathematical and Biological Synthesis (NIMBioS) at the University of Tennessee, Knoxville, to study mate choice.
Their work was published this week in the journal Evolution.
The students began their research between their junior and senior years at Bearden High School in Knoxville. They wanted ...
Stem cells may do best with a little help from their friends
2013-08-27
Like volunteers handing out cups of energy drinks to marathon runners, specially engineered "helper cells" transplanted along with stem cells can dole out growth factors to increase the stem cells' endurance, at least briefly, Johns Hopkins researchers report. Their study, published in the September issue of Experimental Neurology, is believed to be the first to test the helper-cell tactic, which they hope will someday help to overcome a major barrier to successful stem cell transplants.
"One of the bottlenecks with stem cell therapy is the survival of cells once they're ...
Hybrid screening strategy emerges for colorectal cancer
2013-08-27
A strategy that combines two effective colorectal cancer screening methods, fecal immunological test and colonoscopy, may improve prevention and detection of colorectal cancer and reduce costs, according to a new study in Clinical Gastroenterology and Hepatology (CGH), the official clinical practice journal of the American Gastroenterological Association.
The study used a simulation model to test a hybrid screening strategy consisting of annual or biennial fecal immunological test at younger ages (50 to 65 years of age), combined with a single colonoscopy when the patient ...
LAST 30 PRESS RELEASES:
KAIST Develops Retinal Therapy to Restore Lost Vision
Adipocyte-hepatocyte signaling mechanism uncovered in endoplasmic reticulum stress response
Mammals were adapting from life in the trees to living on the ground before dinosaur-killing asteroid
Low LDL cholesterol levels linked to reduced risk of dementia
Thickening of the eye’s retina associated with greater risk and severity of postoperative delirium in older patients
Almost one in ten people surveyed report having been harmed by the NHS in the last three years
Enhancing light control with complex frequency excitations
New research finds novel drug target for acute myeloid leukemia, bringing hope for cancer patients
New insight into factors associated with a common disease among dogs and humans
Illuminating single atoms for sustainable propylene production
New study finds Rocky Mountain snow contamination
Study examines lactation in critically ill patients
UVA Engineering Dean Jennifer West earns AIMBE’s 2025 Pierre Galletti Award
Doubling down on metasurfaces
New Cedars-Sinai study shows how specialized diet can improve gut disorders
Making moves and hitting the breaks: Owl journeys surprise researchers in western Montana
PKU Scientists simulate the origin and evolution of the North Atlantic Oscillation
ICRAFT breakthrough: Unlocking A20’s dual role in cancer immunotherapy
How VR technology is changing the game for Alzheimer’s disease
A borrowed bacterial gene allowed some marine diatoms to live on a seaweed diet
Balance between two competing nerve proteins deters symptoms of autism in mice
Use of antifungals in agriculture may increase resistance in an infectious yeast
Awareness grows of cancer risk from alcohol consumption, survey finds
The experts that can outsmart optical illusions
Pregnancy may reduce long COVID risk
Scientists uncover novel immune mechanism in wheat tandem kinase
Three University of Virginia Engineering faculty elected as AAAS Fellows
Unintentional drug overdoses take a toll across the U.S. unequally, study finds
A step toward plant-based gelatin
ECMWF unveils groundbreaking ML tool for enhanced fire prediction
[Press-News.org] Earthquakes and tectonics in Pamir Tien ShanReal time observation of shear waves on the Earth's surface, first direct observation of subducting continental crust during the collision of two continents