Researchers suggest earthquake lightning may be due to cracks forming in Earth's surface

Mar 07, 2014 by Bob Yirka report
Credit: Jim Conacher

(Phys.org) —A team of four researchers from several universities in the U.S. has given a presentation at this year's American Physical Society meeting, outlining a theory they are developing to help explain a phenomenon known as earthquake lightning.

People have been telling tales of seeing in a cloudless sky just prior to (and sometimes during) earthquakes for several hundred years, though many have ascribed such tales to drinking or hysterics. More recently, however, some have proven it exists by capturing it on video. In this new effort the research team has reported that they may have found its source. Moving material creates , they report, when cracks form. As an example, they found that filling a plastic tub with flour and tilting it back and forth till cracks develop, results in a spike in voltage. Though they are at a loss when trying to explain how or why it happens, they report also that it is very easily repeatable and can happen with many other types of materials as well. They suggest the same sort of thing happens with earthquakes around . The material in the ground is moved back and forth until eventually a crack develops. When that happens, a surge of voltage is unleashed into the atmosphere, creating what observes describe as lightning.

What's perhaps most strange, or interesting about the phenomenon, is that there is no known explanation for it. It doesn't appear to be simple friction, as it occurs with other materials when they separate rather than rub, such as with Scotch tape as it is unreeled, or with Mint Life Savers when they're broken.

The team plans to continue experimenting with various materials, hoping to eventually find an explanation for how such voltage spikes occur, which might help explain why earthquakes don't always generate lightning or why clear sky lightning isn't always followed by an earthquake. Figuring it out, they add, could perhaps lead to a new kind of system (by measuring voltage spikes in the atmosphere) or in developing other applications such as in ceramics to predict impending problems such as a turbine blade about to shatter.

Explore further: New insights into the one-in-a-million lightning called 'ball lightning'

More information: Abstract: S17.00007 : Unexplained voltage signals from granular materials: meetings.aps.org/Meeting/MAR14/Event/214444

via BBC

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tadchem
5 / 5 (4) Mar 07, 2014
I saw earthquake lights in the Sylmar quake (San Fernando Valley, CA, 9 Feb 1971). I was in Santa Susana at the time, and had a great view of the Simi Hills, which lit up all over with what looked like a corona discharge that coincided with the peak of the shaking. I always felt piezoelectric effects had a role.
Bonia
Mar 07, 2014
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nkalanaga
5 / 5 (2) Mar 07, 2014
Bonia: It may BE ball lightning. Not long ago, Phys.org had a story on ball lightning saying it seemed to be caused by vaporized silicon oxides from rocks. In that case, discharges due to earthquakes could well cause it.

http://phys.org/n...deo.html
Caliban
5 / 5 (3) Mar 07, 2014
Piezoelectrics, frictional static electrics, perhaps even magnetic decoupling/reconnection --I suspect any or all, depending on the minerals and type + depth of the fracturing and slipping. All of these factors differ from one site to another, thus, it is no surprise that the observed phenomena differ.
adave
not rated yet Mar 08, 2014
Ball lightning and earthquake lights look to be the same thing. The history of both events occur at fault lines. One article thought they had to be vertical. In my family, ball lightning was observed in 1918 near the Waverly arch in eastern Kentucky with a history of unexplained lights. The area is all sanstone and pizoelectric. We treat the balls like they are solid objects. If you move a dielectric vertically through an electric field nothing is disturbed. So ball lights can look like they are moving horizontally through walls, windows and air because they are projected from underneath. A standing wave produced by a discharge in a fault could cause a ball of plasma to expand and be stable. If this discharge uses the magnetic field of the earth it can couple to the magnetosphere and even solar storms. 5khz is a wavelength on the order of a faultline. See http://en.wikiped..._(radio) Ball discharges should lie in a band not including the equator or the poles.
adave
not rated yet Mar 08, 2014
http://phys.org/n...deo.html article reports vlf fluctuations of 100 hz. Whistler frequencies are 1hz to 5khz. If there is a chain of ball discharges as a standing wave then the next one would be kilometers away and could be 55,000 feet in altitude.
cantdrive85
4.5 / 5 (2) Mar 08, 2014
There are a number of other electrical phenomena associated with earthquakes, the sum of the whole suggests this is more than just rocks rubbing together...
http://www.scient...eund.pdf
Caliban
not rated yet Mar 08, 2014
Thanks for the link, cd85.

Especially important were the notes regarding what conditions were excluded experimentally during research, and what this meant in terms of lost data, and therefore understanding, of the processes involved.