Yesterday, March 16took place a earthquake in japan of magnitude 7.4. It was barely five days after the eleventh anniversary of the earthquake that caused the nuclear disaster of Fukushima. In fact, it was triggered practically in the same neighborhood. This inevitably leads to thinking about the possibility that there is a earthquake season, as is the case with tornadoes or hurricanes. If there were, it would be easier to keep people who live in the most tremor-prone areas alert. However, it’s not that easy. There is no fixed time on the calendaralthough, according to a study published in Science in 2021, in some places, there could be some months with more predisposition.
The study was conducted in Taiwan, where there is a very marked rainy season and a much drier one. It is precisely in the latter that it seems that the drop in groundwater levels could somehow push some kind of earthquake season.
Japan also has a Rainy seasonknown as Tsuyu. However, the differences are not so marked. Therefore, the fact that the last earthquake in Japan took place almost at the same time as that of 2011 seems to be just a coincidence.
Japan earthquake history
The largest earthquake ever recorded in Japan was precisely that of Fukushima in 2011. With a magnitude 9.1 and an intense tsunami behind, left around 9,000 dead and more than 12,000 missing. It was a real tragedy that also included the release of radioactive material from its nuclear power plant.
To see the next magnitude earthquake, we must travel far into the past, to 1707. On October 28 of that year, an earthquake of magnitude 8.6 occurred which affected the southwest of the islands of Honshu and Shikoku and the southeast of Kyūshū. More than 5,000 people died and the material damage was incalculable.
Since then and until this last earthquake in Japan, there has been many more tremors. And the truth is that there doesn’t seem to be a marked season, since they took place in very different months. The most important took place in September 1923, January 1995, March 2001, July 2007, June 2008, August 2009, February 2010, March 2011, January and October 2013, November 2014, May and November 2015 and April and November 2016.
The latter, who for the moment has left 4 dead and 194 injuredhappened a few days before the great disaster of 2011. But, given what has been seen, it seems only a coincidence.
The study published in 2021 analyzed the dates on which major taiwan earthquakes. This country has a very intense rainy season, which takes place from May to September. On the other hand, between October and April, there is what is called the dry season. And that’s where it seems to focus the most earthquakes.
They came to this conclusion after collecting rainfall and seismic data in the country for several centuries. The oldest came from written historical records, while the most recent also included satellite data. This allowed them to have information on the storage of underground water.
They observed that the large variation in precipitation between one half of the year and the other causes a sharp drop in water levels below the ground. Coincidentally (or perhaps causally), the seismic activity coincided precisely with this fall, with a peak of earthquakes in February, March and April. They also observed that at this time the upper layers of the dry earth were rising, which could be related to this curious earthquake season.
However, these data need to be studied much more thoroughly. It is not certain that we can speak of a season as marked as those of tornadoes or hurricanes. In fact, they only observed this correlation in the western part of Taiwan. If you can’t even extrapolate to the rest of the countryeven less should it be used to analyze earthquakes in Japan.
Earthquakes cannot be predicted
There are many false myths about earthquakes. For example, it is often said that many small earthquakes avoid a large one because ground stresses are relieved. And also the opposite: that many small ones are the prelude to a great tremor.
It may or may not happen. There are no factors that can predict an earthquake beyond the ground. There is also no earthquake season where you have to be more careful. Yes, there are more prone places, because they are on subduction zones. These are points where one lithospheric plate sinks under another. The stresses caused by friction between its edges are what can give rise to earthquakes. And Japan stands on the Ring of Firewhich is one of the largest subduction zones in the world.
Too Taiwan it is on this same belt, responsible for significant seismic and volcanic events. But that also doesn’t mean the 2021 study can be extrapolated to the Earthquakes in Japan.
Therefore, while it would be good to have a specific time of the year when the Japanese could be vigilant, given their country’s circumstances and the scientific evidence, it is better that they be so all of the time. year. In fact, it is one of the best prepared countries to withstand an earthquake. It is not for less, given its history.