Are the moon and tides capable of causing large earthquakes?

By David Jacobson, Temblor

Could the moon really be a key to unlocking when large earthquakes will occur?

Photo: Maxime Raynal
Photo: Maxime Raynal

In an article published today in Nature Geoscience, tidal reconstructions done by a team of Japanese scientists appear to show that large subduction zones are highly sensitive to changes from tidal stresses. By analyzing and simulating tides in the two weeks prior to large events (e.g. 2004 Sumatra, 2010 Chile, and 2011 Tohoku), they found that the earthquakes tended to occur at times of maximum stress.

As can be seen from the above image, the 2004 M=9.3 Sumatra earthquake occurred during a period of maximum tidal stress. In total, the Japanese team found that of the 12 largest earthquakes ever recorded, nine fell on or near days with full or new moons.
As can be seen from the above image, the 2004 M=9.3 Sumatra earthquake occurred during a period of maximum tidal shear stress. In total, the Japanese team found that of the 12 largest earthquakes ever recorded, nine fell on or near days with full or new moons. For comparison, 1 kPa is equivalent to 1.5 ounces/square inch. In other words, it is extremely small, but applied over an extremely large area.

 

The Japanese team, led by Dr. Satoshi Ide, is not predicting when earthquakes will occur. However they are suggesting when large magnitude earthquakes are slightly more likely to occur. They are quick to point out though that this study only applies to large magnitude earthquakes and that a relationship between tidal stress and smaller magnitude earthquakes remains “elusive.” Nonetheless, the large earthquakes they examined caused huge damage and resulted in significant loss of life.

The devastating 2001 Tohoku earthquake and ensuing tsunami caused billions of dollars of damage and the deaths of thousands. A new Japanese study suggests that tidal stresses could influence large magnitude subduction zone earthquakes. Photo from: SFDEM
The devastating 2011 Tohoku earthquake and ensuing tsunami caused billions of dollars of damage and the deaths of thousands. A new study suggests that tidal stresses could influence large magnitude earthquakes. Photo from SFDEM

 

While tidal influence on earthquakes has been debated since the 19th century, most scientists remain unconvinced. This is largely due to the difficulty in producing reliable data, as well as the fact that tides impart such as small amount of stress when compared to tectonic forces. However, this study is one of the the few to show a statistical link, and has already turned heads.

In an interview with USA Today, University of Washington seismologist Dr. John Vidale said, “Scientists will find this result, if confirmed, quite interesting.” However, just because scientists find something interesting does not mean they will jump on the bandwagon. Additionally, Vidale pointed out that because the likelihood of deadly earthquakes occurring on a weekly basis is so infinitesimal, this study won’t help with predictions.

Furthermore, even if a clear correlation is found, it is unlikely the information will be able to be used in a practical sense. Mark Quigley, University of Melbourne associate professor in active tectonics and geomorphology, and this author’s former supervisor, said in an interview that he doesn’t see any practical use “in the context of coastal seismic hazard and public safety,” especially when compared to building codes and tsunami evacuation plans. This is likely true as evacuating coastal regions during times of increased tidal stress is unlikely to catch on.

Despite this caveat, the new study does lend itself towards potentially opening a door in determining when and how subduction zone earthquakes occur. It is likely that from this work, greater attention will be given to tidal stresses when assessing when earthquakes occur. Now we just have to see if the theory stands the test of time.

Sources:
Nature Geoscience: Earthquake potential revealed by tidal influence on earthquake size–frequency statistics
Stein R. S., Tidal triggering caught in the act. Science, 2004, 305: 1248–1249 Link
Nature: Moon’s pull can trigger big earthquakes
USA Today
Stuff.co.nz

  • mlyd

    The Tuhoku Earthquake was in 2011, not 2001 as stated in the picture caption.