Gravity sensors might offer earlier warning of earthquakes

earthquake
Ruins from the 1906 San Francisco earthquake, remembered as one of the worst natural disasters in United States history. Credit: Public Domain

(Phys.org)—A team of researchers from France, the U.S. and Italy has found evidence from the Tohoku-Oki earthquake that sensors that measure changes in gravity might offer a way to warn people of impending disaster faster than traditional methods. In their paper published in the journal Nature Communications, the group describes how they analyzed data from gravity sensors near the epicenter of the Tohoku-Oki quake back in 2011 and found that it was possible to isolate gravitational changes due to the earthquake from the noise of other events.

Current earthquake warning systems rely on a network of seismic —they listen for P-waves below the ground which are generated by an earthquake and send a signal to an alarm if they are heard. Such a system offers those in the vicinity of a quake from a few seconds to perhaps a minute to take safety measures. In this new effort, the researches wondered if it might be possible to detect subtle changes in near the epicenter of a quake to offer those in harm's way a little more time to prepare for it—because waves travel at the speed of light.

Prior research has shown that there are subtle changes in gravitational pull around the epicenter of a quake, due to changes in the density of the rock in the area. But until now, it was not clear if such changes could be picked out from all the other background noise. To find out, the researchers pulled data from gravimeter sensors located approximately 500 kilometers from the epicenter of the Tohoku-Oki quake and compared what they found in the record with data from five in the same area. They noted also that it took 65 seconds for the P-waves to reach the seismic stations. To find out if the quake data would stand out amongst the noise of other natural events (such as the changing tides) the team looked at measurements taken over the 60 days prior to the quake and then at the data from the day before, the day of, and the day after the quake. In looking at the data, the researchers found that they were able to "see" a small blip—one that stood out enough to confirm a quake had occurred.

More research will have to be done before it can be proven that a network of gravity sensors would truly offer people more time to prepare for a (depending on how close they are to the ), but the results from this initial study seem promising.


Explore further

Homing in on a potential pre-quake signal

More information: Jean-Paul Montagner et al. Prompt gravity signal induced by the 2011 Tohoku-Oki earthquake, Nature Communications (2016). DOI: 10.1038/ncomms13349

Abstract
Transient gravity changes are expected to occur at all distances during an earthquake rupture, even before the arrival of seismic waves. Here we report on the search of such a prompt gravity signal in data recorded by a superconducting gravimeter and broadband seismometers during the 2011 Mw 9.0 Tohoku-Oki earthquake. During the earthquake rupture, a signal exceeding the background noise is observed with a statistical significance higher than 99% and an amplitude of a fraction of μGal, consistent in sign and order of magnitude with theoretical predictions from a first-order model. While prompt gravity signal detection with state-of-the-art gravimeters and seismometers is challenged by background seismic noise, its robust detection with gravity gradiometers under development could open new directions in earthquake seismology, and overcome fundamental limitations of current earthquake early-warning systems imposed by the propagation speed of seismic waves.

Journal information: Nature Communications

© 2016 Phys.org

Citation: Gravity sensors might offer earlier warning of earthquakes (2016, November 23) retrieved 18 July 2019 from https://phys.org/news/2016-11-gravity-sensors-earlier-earthquakes.html
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Nov 24, 2016
If there is a desire to actually predict large earthquakes rather than just react, such as what is proposed above, then we may need to keep a close eye on the Sun.
http://www.suspic...hquakes/

Nov 24, 2016
^ Indeed cantdrive85, I've been following Ben and company for quite some time now, due to being heavily interested in all the significant ways our planet is electromagnetically connected to the Sun and the entire solar system. What this article actually does however, is provide even more confirmation that Gravity is actually electrical in nature, rather than relying on mass to be it's driving force, which would be completely expected if it could fluctuate at all. This is especially significant due to earthquakes coinciding with the fluctuations in question, coupled with what the S0s know about the Sun's magnetic influence playing a huge role in predicting them. When you also factor in the spikes in static electricity that occur immediately prior to earthquakes, then the discussion becomes even more tilted in the direction of electromagnetism.

Nov 24, 2016
^^^^^^^Complete and utter drivel! The Sun causes earthquakes! Yeah, right. This idiot Davidson's rubbish was the subject of a long running thread on ISF a while back: (http://www.intern...quakes).
A bit of statistical analysis shows that it is complete rubbish. No better than the crap you see from tabloid psychics. I made an earthquake prediction in that thread, based on days when I had bacon for breakfast. Guess what? I got it right! Difference is, I didn't post my amazing hypothesis on a crank science website, claiming that the eating of bacon for breakfast was responsible for earthquakes. However, it is as valid as this rubbish.

Nov 24, 2016
When you also factor in the spikes in static electricity that occur immediately prior to earthquakes, then the discussion becomes even more tilted in the direction of electromagnetism.


Err, no. Ever heard of spreading centres? Like the mid-Atlantic ridge? Tectonic plates? Plates are pushed apart by the spreading centres. Oceanic crust is denser than continental crust. When the two meet, something has to give. The denser oceanic plate dives below the continental crust, such as along the west coast of South America. This causes earthquakes. As the plate continues to dive down, it melts. That causes volcanoes.
As was explained in high school science, for those that paid attention. No woo needed to explain something that is perfectly well understood.
http://platetecto...t.co.uk/


Nov 24, 2016

Oceanic crust is denser than continental crust. When the two meet, something has to give. The denser oceanic plate dives below the continental crust, such as along the west coast of South America. This causes earthquakes. As was explained in high school science, for those that paid attention. No woo needed to explain something that is perfectly well understood.

Gotta love the excitable internet pom pom waving that some people do, and this guy just loves to tell people they're wrong. Putting all of that bravado aside however, a lot of what we've been taught in high school (for us who were paying attention) was simply the best guess scientists at the time had, and many of these theories were unproven. While plate tectonics might be happening at some level, no one has dug that far down to prove it's responsible for all earthquakes and volcanoes. It's indisputable that fault lines exist, but there's a lot of fluid present within those faults that can conduct electricity.

Nov 24, 2016
Another few good questions concerning plate tectonics would be: If one entire plate is shifting under another plate, then why is there an epicenter to the quake? Shouldn't the whole plate rumble and not one specific radius? Why does the quake appear focused? Why would gravity fluctuate if it's something as simple as kinetic vibration? Lastly, and most importantly, what progress towards quake prediction have the mainstream scientists made? What makes jonesdave so certain of his correctness?

Nov 25, 2016
This comment has been removed by a moderator.

Nov 25, 2016
@Peon,
While plate tectonics might be happening at some level.......


Yep, a measured level in some cases:
http://web.pdx.ed...1994.pdf
http://onlinelibr...780/full
And there are other similar papers for different plates, as mentioned here:
http://expansion....011.net/
Try reading and, more importantly, understanding them.

As for why earthquakes don't happen all along the fault - that would involve you actually having to educate yourself in the subject. There is plenty of stuff out there; read it. For somebody who believes in electrical woo from the Sun causing earthquakes however, that seems unlikely to happen.

Thankfully, nobody takes Sun caused earthquakes seriously. Nobody that matters, anyway.

Nov 25, 2016
This comment has been removed by a moderator.

Nov 27, 2016
Those were great links and provided a good read, although none of them stated their findings were 100% indicative that plate shifting had anything to do with earthquakes. Rather it seemed, they only managed to verify subduction while proving many other claims were not valid, and never ended up predicting or verifying the causes of any quakes. Here are some great quotes:

1st link:
Although not conclusive in itself, our measurement of corivergence between Christmas Island and Cocos Island and West Java provides a constraint on possible mechanisms of subduction occurring on this section of the Java Trench.


2nd link:
No significant variations are detected for the baselines within the Australia plate.


3rd link:
As with Wegener's Continental Drift, time will tell, but for now, Plate Tectonics is the best planetary tectonic theory available to science.


Scientific research should always be respected, so make sure you respect the Heliophysicists as well.

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