PRESS-NEWS.org - Press Release Distribution
PRESS RELEASES DISTRIBUTION

Earthquake lights linked to rift environments, subvertical faults

2014-01-02
(Press-News.org) Contact information: Nan Broadbent
press@seismosoc.org
408-431-9885
Seismological Society of America
Earthquake lights linked to rift environments, subvertical faults

SAN FRANCISCO – Rare earthquake lights are more likely to occur on or near rift environments, where subvertical faults allow stress-induced electrical currents to flow rapidly to the surface, according to a new study published in the Jan./Feb. issue of Seismological Research Letters.

From the early days of seismology, the luminous phenomena associated with some earthquakes have intrigued scholars. Earthquake lights (EQL) appear before or during earthquakes, but rarely after.

EQL take a variety of forms, including spheres of light floating through the air. Seconds before the 2009 L'Aquila, Italy earthquake struck, pedestrians saw 10-centimeter high flames of light flickering above the stone-paved Francesco Crispi Avenue in the town's historical city center. On Nov. 12, 1988, a bright purple-pink globe of light moved through the sky along the St. Lawrence River near the city of Quebec, 11 days before a powerful quake. And in 1906, about 100 km northwest of San Francisco, a couple saw streams of light running along the ground two nights preceding that region's great earthquake.

Continental rift environments now appear to be the common factor associated with EQL. In a detailed study of 65 documented EQL cases since 1600 A.D., 85 percent appeared spatially on or near rifts, and 97 percent appeared adjacent to subvertical faults (a rift, a graben, strike-slip or transform fault). Intraplate faults are associated with just 5 percent of Earth's seismic activity, but 97 percent of documented cases of earthquake lights.

"The numbers are striking and unexpected," said Robert Thériault, a geologist with the Ministère des Ressources Naturelles of Québec, who, along with colleagues, culled centuries of literature references, limiting the cases in this study to 65 of the best-documented events in the Americas and Europe.

"We don't know quite yet why more earthquake light events are related to rift environments than other types of faults," said Thériault, "but unlike other faults that may dip at a 30-35 degree angle, such as in subduction zones, subvertical faults characterize the rift environments in these cases."

Two of the 65 EQL events are associated with subduction zones, but Thériault suggests there may be an unknown subvertical fault present. "We may not know the fault distribution beneath the ground," said Thériault. "We have some idea of surface structures, but sedimentary layers or water may obscure the underlying fault structure."

While the 65 earthquakes ranged in magnitude, from M 3.6 to 9.2, 80 percent were greater than M 5.0. The EQL varied in shape and extent, though most commonly appeared as globular luminous masses, either stationary or moving, as atmospheric illuminations or as flame-like luminosities issuing from the ground.

Timing and distance to the epicenter vary widely. Most EQL are seen before and/or during an earthquake, but rarely after, suggesting to the authors that the processes responsible for EQL formation are related to a rapid build-up of stress prior to fault rupture and rapid local stress changes during the propagation of the seismic waves. Stress-activated mobile electronic charge carriers, termed positive holes, flow swiftly along stress gradients. Upon reaching the surface, they ionize air molecules and generate the observed luminosities.

Eyewitness reports and security cameras captured a large number of light flashes during the 2007 Pisco, Peru M 8.0 earthquake. Together with seismic records obtained on a local university campus, the automatic security camera records allow for an exact timing and location of light flashes that illuminated a large portion of the night sky. The light flashes identified as EQL coincided with the passage of the seismic waves.

Thériault likes the account of a local L'Aquila resident, who, after seeing flashes of light from inside his home two hours before the main shock, rushed his family outside to safety.

"It's one of the very few documented accounts of someone acting on the presence of earthquake lights," said Thériault. "Earthquake lights as a pre-earthquake phenomenon, in combination with other types of parameters that vary prior to seismic activity, may one day help forecast the approach of a major quake," said Thériault.



INFORMATION:



ELSE PRESS RELEASES FROM THIS DATE:

Longmanshen fault zone still hazardous, suggest new reports

2014-01-02
Longmanshen fault zone still hazardous, suggest new reports Seismological Research Letters publishes special issue on 2013 Lushan, China earthquake SAN FRANCISCO – The 60-kilometer segment of the fault northeast of the 2013 Lushan rupture is the place ...

Jumping DNA in the brain may be a cause of schizophrenia

2014-01-02
Jumping DNA in the brain may be a cause of schizophrenia Stretches of DNA called retrotransposons, often dubbed "junk DNA", might play an important role in schizophrenia. In a study published today in the journal Neuron, a Japanese team revealed that LINE-1 retrotransposons are abnormally ...

Roses are red -- why some petunias are blue

2014-01-02
Roses are red -- why some petunias are blue Researchers have uncovered the secret recipe to making some petunias such a rare shade of blue. The findings may help to explain and manipulate the color of other ornamental flowers, not to mention the taste of fruits and wine, say ...

Plant used in Chinese medicine fights chronic pain

2014-01-02
Plant used in Chinese medicine fights chronic pain A plant used for centuries as a pain reliever in Chinese medicine may be just what the doctor ordered, especially when it comes to chronic pain. A key pain-relieving ingredient is a compound known as dehydrocorybulbine (DHCB) ...

JCI early table of contents for Jan. 2, 2014

2014-01-02
JCI early table of contents for Jan. 2, 2014 Opioid tolerance and pain hypersensitivity associated with mTOR activation Currently, opioids are the standard treatment for chronic pain. Patients on opioids for long periods of time become desensitized to ...

Opioid tolerance and pain hypersensitivity associated with mTOR activation

2014-01-02
Opioid tolerance and pain hypersensitivity associated with mTOR activation Currently, opioids are the standard treatment for chronic pain. Patients on opioids for long periods of time become desensitized to these drugs or become paradoxically hypersensitive ...

Doxorubicin-associated mitochondrial iron accumulation promotes cardiotoxicity

2014-01-02
Doxorubicin-associated mitochondrial iron accumulation promotes cardiotoxicity Doxorubicin is a widely used as a component of chemotherapy regimes; however, the use of doxorubicin is associated with severe cardiotoxicity. It is unclear exactly how doxorubicin ...

Biologists discover solution to problem limiting development of human stem cell therapies

2014-01-02
Biologists discover solution to problem limiting development of human stem cell therapies Biologists at UC San Diego have discovered an effective strategy that could prevent the human immune system from rejecting the grafts derived from human embryonic ...

Study on pregnancy and alcohol fails to take psychological factors into account

2014-01-02
Study on pregnancy and alcohol fails to take psychological factors into account "It is OK to drink a little bit of alcohol during pregnancy" or "a pregnant woman should not touch alcohol at all during her pregnancy". These statements represent the ...

Brain training works, but just for the practiced task, say Oregon researchers

2014-01-02
Brain training works, but just for the practiced task, say Oregon researchers Revealing pattern of changes detected in brain using MRI as 'trained' subjects show improved self-control EUGENE, Ore. -- Search for "brain training" on the Web. You'll find online exercises, ...

LAST 30 PRESS RELEASES:

Are lifetimes of big appliances really shrinking?

Pink skies

Monkeys are world’s best yodellers - new research

Key differences between visual- and memory-led Alzheimer’s discovered

% weight loss targets in obesity management – is this the wrong objective?

An app can change how you see yourself at work

NYC speed cameras take six months to change driver behavior, effects vary by neighborhood, new study reveals

New research shows that propaganda is on the rise in China

Even the richest Americans face shorter lifespans than their European counterparts, study finds

Novel genes linked to rare childhood diarrhea

New computer model reveals how Bronze Age Scandinavians could have crossed the sea

Novel point-of-care technology delivers accurate HIV results in minutes

Researchers reveal key brain differences to explain why Ritalin helps improve focus in some more than others

Study finds nearly five-fold increase in hospitalizations for common cause of stroke

Study reveals how alcohol abuse damages cognition

Medicinal cannabis is linked to long-term benefits in health-related quality of life

Microplastics detected in cat placentas and fetuses during early pregnancy

Ancient amphibians as big as alligators died in mass mortality event in Triassic Wyoming

Scientists uncover the first clear evidence of air sacs in the fossilized bones of alvarezsaurian dinosaurs: the "hollow bones" which help modern day birds to fly

Alcohol makes male flies sexy

TB patients globally often incur "catastrophic costs" of up to $11,329 USD, despite many countries offering free treatment, with predominant drivers of cost being hospitalization and loss of income

Study links teen girls’ screen time to sleep disruptions and depression

Scientists unveil starfish-inspired wearable tech for heart monitoring

Footprints reveal prehistoric Scottish lagoons were stomping grounds for giant Jurassic dinosaurs

AI effectively predicts dementia risk in American Indian/Alaska Native elders

First guideline on newborn screening for cystic fibrosis calls for changes in practice to improve outcomes

Existing international law can help secure peace and security in outer space, study shows

Pinning down the process of West Nile virus transmission

UTA-backed research tackles health challenges across ages

In pancreatic cancer, a race against time

[Press-News.org] Earthquake lights linked to rift environments, subvertical faults