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Geophysicists Discover How Rocks Produce Magnetic Pulses 72

KentuckyFC (1144503) writes "Since the 1960s, geophysicists have known that some earthquakes are preceded by ultra-low frequency magnetic pulses that increase in number until the quake takes place. But this process has always puzzled them: how can rocks produce magnetic pulses? Now a group of researchers has worked out what's going on. They say that rocks under pressure can become semiconductors that produce magnetic pulses under certain circumstances.

When igneous rocks form in the presence of water, they contain peroxy bonds with OH groups. Under great temperature and pressure, these bonds break down creating electron-holes pairs. The electrons become trapped at the site of the broken bonds but the holes are free to move through the crystal structure. The natural diffusion of these holes through the rock creates p and n regions just like those in doped semiconductors. And the boundary between these regions behaves like the p-n junction in a diode, allowing current to flow in one direction but not the other. At least not until the potential difference reaches a certain value when the boundary breaks down allowing a sudden increase in current. It is this sudden increase that generates a magnetic field. And the sheer scale of this process over a volume of hundreds of cubic meters ensures that these magnetic pulses have an extremely low frequency that can be detected on the surface. The new theory points to the possibility of predicting imminent earthquakes by triangulating the position of rocks under pressure by searching for the magnetic pulses they produce (although significantly more work needs to be done to characterize the process before then)."
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Geophysicists Discover How Rocks Produce Magnetic Pulses

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  • by ctrl-alt-canc ( 977108 ) on Wednesday June 04, 2014 @05:35PM (#47167881)
    IAAP (I am a physicist), and my work field concerns also geophysics. TFA is very suspicious for several reasons. I just list the simplest points to understand

    First, there are way too much self references: take for example the first sentence "Rocks, especially igneous rocks, behave as semiconduc- tors under certain conditions". They connect this sentence to four papers previously published by one of the authors (Freund). Nobody else in the scientific world ever verified that rocks are semiconductors ?!? This does not make a good start for the topic they are going to discuss.

    The authors claim that it is more than 50 years that the boundary between earthquakes and VLF emission has been established. Unfortunately this is not true: if it were, seismic network would be composed of radio receivers, they are way cheaper than seismometers. The existence of a connection between VLF emission and earthquakes is still an open question, and there are no conclusive proofs supporting it.
    What we know is that earthquakes are usually not associated to a simultaneous VLF emission, so a theory explaining how earthquake precursors can trigger a VLF emissions should also justify why earthquakes have no VLF emission as well.

    Figure 1 of TFA is a masterpiece of deception: please look at the value range in the graphs showing the computed and measured events: do you still think that the numerical predictions estimated by the authors and the field measurements can be defined "similar" ?!? They only share the same shape, when drawn on very different time and amplitude ranges!

    Summing up, I am afraid that this paper isn't going to be of any help with earthquake prediction...the next, please!

"Pascal is Pascal is Pascal is dog meat." -- M. Devine and P. Larson, Computer Science 340