Naked Science Forum
Non Life Sciences => Geology, Palaeontology & Archaeology => Topic started by: Kurt Schallitz on 28/09/2009 08:30:05
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Kurt Schallitz asked the Naked Scientists:
Hi Scientists,
It's Kurt from California. I'm just getting caught up on my podcasts (http://www.thenakedscientists.com/HTML/podcasts/) and doing a marathon of Naked Scientists. It's like a little piece of heaven.
Anyhow, I was listening to the idea of weather patterns (typhoons) causing slow earthquakes. This led me to make a connection with something we in California have always called "Earthquake Weather".
Those of us who have lived here for sometime usually can look outside and very often make the statement of "Looks like earthquake weather." Usually this is at times when there are storms in the area. Big storms are fairly rare around here in San Francisco Bay. I was curious if there was perhaps something to this notion after all.
As a skeptic I've always assumed it was just confirmation bias - someone says "Hey looks like earthquake weather today" perhaps 20 times a year and only recalls the one time when an earthquake does occur.
However, after listening to your podcast (http://www.thenakedscientists.com/HTML/podcasts/), I'm curious if perhaps there really is
something to a high / low pressure system causing pressure changes on the many, many faults in this area and actually causing minor quakes.
Great Podcasts (http://www.thenakedscientists.com/HTML/podcasts/) - keep them coming!
Kurt Schallitz
What do you think?
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The science for the connection is VERY shaky. The pressure of the atmosphere is many, many magnitudes lower than the pressure that causes earthquakes.
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I've heard of some hypothesis that put the causality the other way around, largely based upon piezoelectric effects.
That there will be some degree of piezoelectric factor is almost certain, but as to whether that factor has any significance is totally open to debate.
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I am unfamiliar with piezoelectric factors and had to look it up...
Now having examined the meaning a tad I can still say I do not fully understand it.. but know that it is where certain materials can generate electric potential through temperature changes.
So I am familiar with th original phrase about "Earthquake weather." and now understand the reference.... So I am understanding that crystals and certain ceramics including bones have the potential to create electricity during temperature changes I am assuming that includes the changes in atmospheric pressures as well as inner core changes also. Is that correct and if not how far off am?
So there have been many times here in Northern California where I have experienced what we feel is Earthquake weather and it is usually not exactly sultry but also very quiet and the air seems different..... very weird.. We experienced this right before the 7.2 several years ago here in upper Northern Califorina!
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The air seems heavier thicker if you know what I mean.. could this be explained by barometric atmospheric pressure change?
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Hmm... where did you find the reference to temperature change in connection with piezoelectricity?
It's actually stress in the material that generates the electric charge i.e. by bending or striking it. This is how many cigarette and gas lighters work: the trigger draws back a small sprung hammer which, when released, strikes a piece of piezo crystal, most probably quartz, which then generates the electricity for the spark. The opposite effect works too, so it's possible to apply electricity to a piezo crystal and make it move: this principle is often used in high-power high-frequency loudspeaker drivers as the crystal can be made to vibrate by applying a signal to it.
Anyway, the possible link between the piezoelectric effect and earthquakes then, is through the stresses in the rock that are built up and released during earthquakes. However, most of any piezoelectric effect is likely to occur during a quake, and not before it. Although a lot of stress will have built up, up to the point of the quake, it would have been over a long period of time and most of the charge generated will have leaked back to earth. When the quake does occur though, you'll get a lot of rock moving against other rock, striking and bending, and then releasing it, so that's when any piezoelectric effect is likely to be at its greatest. This doesn't quite rule out precursor effects, but they would require a pretty fast and sudden build up of stress immediately before the quake, and I don't know if this has been witnessed or even how plausible it is.
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http://en.wikipedia.org/wiki/Piezoelectricity
Discovery and early research
The pyroelectric effect, where a material generates an electric potential in response to a temperature change, was studied by Carolus Linnaeus and Franz Aepinus in the mid-18th century. Drawing on this knowledge, both René Just Haüy and Antoine César Becquerel posited a relationship between mechanical stress and electric charge; however, experiments by both proved inconclusive.
The first demonstration of the direct piezoelectric effect was in 1880 by the brothers Pierre Curie and Jacques Curie. They combined their knowledge of pyroelectricity with their understanding of the underlying crystal structures that gave rise to pyroelectricity to predict crystal behavior, and demonstrated the effect using crystals of tourmaline, quartz, topaz, cane sugar, and Rochelle salt (sodium potassium tartrate tetrahydrate). Quartz and Rochelle salt exhibited the most piezoelectricity.
A piezoelectric disk generates a voltage when deformed (change in shape is greatly exaggerated)
The Curies, however, did not predict the converse piezoelectric effect. The converse effect was mathematically deduced from fundamental thermodynamic principles by Gabriel Lippmann in 1881.[2] The Curies immediately confirmed the existence of the converse effect, and went on to obtain quantitative proof of the complete reversibility of electro-elasto-mechanical deformations in piezoelectric crystals.
For the next few decades, piezoelectricity remained something of a laboratory curiosity. More work was done to explore and define the crystal structures that exhibited piezoelectricity. This culminated in 1910 with the publication of Woldemar Voigt's Lehrbuch der Kristallphysik (textbook on crystal physics), which described the 20 natural crystal classes capable of piezoelectricity, and rigorously defined the piezoelectric constants using tensor analysis.
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Ah right - you threw me there by referring to the pyroelectric effect, not the piezoelectric effect.
I guess that does suggest a theoretical link between weather and earthquakes though i.e. high weather temperatures could induce a pyroelectric effect in the rocks, the electricity from which then induces additional piezoelectric stresses that might take the total stress above the earthquake threshold.