Moon’s Gravitational Pull Can Influence Quakes

First Posted: Sep 14, 2016 05:40 AM EDT
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The Moon's gravitational pull is responsible for tides on Earth, but a new research suggests this force may also have a role in triggering big earthquakes. Tides happen as the Moon and the Sun gravitationally pull the rotating Earth. Many researches have been conducted to ascertain if this gravitational force affect Earth's tectonic faults. But a research team at the University of Tokyo looked into the relationship between the recent big earthquakes in Japan, Chile, and Indonesia and tidal changes during syzygies, or full or new Moon.

The team, led by seismologist Satoshi Ide, published their findings in the journal Nature Geoscience. "Large quakes are more probable during periods of high tidal stress," they noted. The team looked into the change and size in tidal stress during the magnitude 9.3 earthquake in Sumatra, Indonesia in 2004; the magnitude 8.8 quake in Maule, Chile in 2010; and the magnitude 9.0 in Tohoku, Japan in 2011.

The seismologists found a correlation between the destructive quakes and periods of high tidal stress changes. They also said that nine out of the 12 biggest earthquakes recorded occurred near or during syzygies. But the underlying mechanism in the correlation was unknown, they added.

According to the team, deep within subduction zones, tectonic movements react and are "highly sensitive" to tidal stress. They assume that intense tidal stress increases the probability of earthquakes and tectonic deformation in these zones. 

However, the researchers said the increased tidal stress is "not obvious" in small quakes. But "knowledge of the tidal stress state in seismic regions can be used to improve probabilistic earthquake forecasting, especially for extremely large earthquakes" the Japanese team said.

The study has received mixed reactions from several seismologists around the world. John Vidale at the University of Washington in Seattle said the findings were "interesting," though predictions from these correlations could be "rather unhelpful." Meanwhile, Honn Kao at the Geological Survey of Canada said the study was an "innovative way to address the issue [whether tides cause earthquakes]."

Last July, a study from the U.S. Geological Survey led by seismologist Nicholas J. van der Elst suggested that the earthquakes in San Andreas fault in California have been caused by gravitational pull of the Moon and the Sun. It explained that daily tides could trigger small quakes, while larger and faster ones happen when the Moon is in the same direction of the fault.

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