Statistical analysis suggests Moon can cause quakes

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The uncertainty of science: A careful statistical analysis of when major earthquakes occur has suggested they are more likely to be more powerful if they occur around the full and new moons when tidal forces are at their peak.

Satoshi Ide, a seismologist at the University of Tokyo, and his colleagues investigated three separate earthquake records covering Japan, California and the entire globe. For the 15 days leading up to each quake, the scientists assigned a number representing the relative tidal stress on that day, with 15 representing the highest. They found that large quakes such as those that hit Chile and Tohoku-Oki occurred near the time of maximum tidal strain — or during new and full moons when the Sun, Moon and Earth align.

For more than 10,000 earthquakes of around magnitude 5.5, the researchers found, an earthquake that began during a time of high tidal stress was more likely to grow to magnitude 8 or above.

As these results are based entirely on statistical evidence, not on any direct link between tidal forces and actual quakes, they are quite uncertain and unproven.


  • Localfluff

    It shouldn’t be too far fetched to make a theoretical justification too. That tidal forces of passing moons crack the surface of Europa and cause volcanoes on Io is pretty obvious.

  • Edward

    I have long suspected a connection. The Loma Prieta earthquake in 1989 (south of San Francisco) occurred about 5 PM, as the sun was setting, and the San Francisco earthquake in 1906 occurred aobut 5 AM, as the sun was rising. Solar tidal forces would have been “pulling apart” the San Andreas Fault in both cases.

    The moon was three days past full moon for the Loma Prieta quake, and three days before new moon for the San Francisco quake. Although it would seem, under this hypothesis, that Loma Prieta should have happened three days earlier, when the sun and moon lined up better for an even greater amount of tugging on the fault, I cannot help but wonder whether the combined tidal forces of the sun and the moon have an effect on slip faults that run generally north-south.

    Although statistics cannot determine cause for an observed effect, as Robert noted, it does show that the observation may be worth investigation.

  • Localfluff

    There seems to be well established ideas about this. Maybe it would help to study Moon quakes too.

  • Lee S

    I had a long online argument with a professor of geology and physics about this subject about 7-8 years ago, he refused to even consider the possibility, but as water levels contribute to slippage of faults, it seemed obvious to me that a higher tidal water level combined with a slightly higher gravity pull from the moon might contribute to a higher possibility of earthquakes… My admittedly fast and loose research indicated between 5 and 10% increase in likelyhood of a major quake at or around new moons ( IIRC )…
    The professor called me a woo spreader and said he would rate me F if he was my teacher… I may have to look him up again…

  • Lee S: Be very careful. The study cited here did not find that tidal forces caused more earthquakes. The study found that statistically the magnitude of quakes seems to increase during periods of strong tides.

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