Japanese Team Finds Full Moon May Up Earthquake Risk

Full moon above Greek village

A group of Japanese scientists found the world’s most destructive earthquakes occurred around a full or new moon. Researchers explained the tension exerted on the Earth’s crust by the moon is strong enough to trigger quakes.

Researchers reported they found a pattern in the incidence of the planet’s most devastating earthquakes. For instance, this is the case with the so-called “Boxing Day earthquake” in the Indian Ocean whose monster tsunamis killed more than 200,000 people.

The moon seems to be the culprit in an 8.8-magnitude earthquake in southern Chile six years ago, which killed 525 people, and in the 2011 earthquake in Japan which resulted in 15,800 casualties and a leakage at a Fukushima nuclear power plant.

Study authors explained that such large earthquakes occur when the small breakages in the fault lines turn into huge ruptures under the Moon’s strain.

The Findings Could Help with Better Prediction Models

Lead author of the study Satoshi Ide now hopes the findings would help humanity issue better prediction models for large earthquakes.

Japan is notorious for its intense seismic activity. According to Earthquaketrack.com, Japan saw 17 earthquakes in the last seven days, and 56 over the last month. In 2015, it had 673 earthquakes.

Prof Ide explained that small earthquakes occur on a daily basis worldwide too. But a tiny fraction of these quakes somehow morph into natural disasters. Scientists have tried for years to estimate the size of an earthquake by analyzing the initial rupture in the fault lines.

Prof Ide added that current models can only predict larger events “probabilistically.” But using extra data from the Moon’s tidal stress on quake-prone regions could greatly improve those models. The extra data can be especially useful in predicting extremely large earthquakes, according to Prof. Ide.

The Moon, the Sun, and Tides

Both the Sun and the Moon’s gravitational pull on the Earth can cause tidal stress. Ancient people have long known that the moon’s gravitational pull causes tides on Earth. But the strongest tide is the “spring tide,” which happens twice a month.

Spring tides occur in two scenarios: when a full moon is located on the other side of our planet, facing the Sun, or a new moon is located on the same side as the Sun. In these two instances, researchers explained, the moon’s gravitational tug combines with the Sun’s. This is why the ocean bulges more triggering the impressive tides.

However, the Japanese team believes that the same forces place an additional stress on the Earth’s crust too. But no study has been so far able to prove that.

No Link to Smaller Quakes

So, Prof. Ide’s team sifted through data on seismic activity two weeks prior to a major quake. They were not able to find an association between tidal stress and lower-magnitude quakes, but they did find a link with larger ones.

According to the findings, the world’s most devastating earthquakes happened when tidal stresses reached their highest point. Researchers concluded that the larger the tidal stress level, the higher the probability of a large earthquake is.

Scientists published their work this week in the journal Nature Geoscience.

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