The warning issued by the Japan Seismological Service was for a severe earthquake of at least magnitude 7 in the Nankai Slope, saying that the probability of it occurring is very high. This naturally caused concern, recalls the German public broadcaster ZDF. A week later, the government lifted the warning, but fears of a major disaster remained. Back in 2013, a team specializing in disaster prevention calculated that a 9.1-magnitude earthquake in the Nankai Basin could trigger a tsunami that would exceed a height of ten meters in minutes. In this situation, up to 323,000 people could die, and over two million buildings could be destroyed.
But how likely are earthquakes of this magnitude to become more frequent, which regions would be affected, and how could people be protected from them? ZDF seeks the answers from seismologist Frederik Tillmann.
What are "megaearthquakes" and how common are they?
For the experts, the term “megaearthquake” no, Professor Frederik Tillmann from the German Georesearch Center in Potsdam points out to the German public law media. He clarifies that large and severe earthquakes are defined as earthquakes with a force above the seventh degree. In this particular case, the Japanese authorities had warned of a “megaquake” of the eighth or ninth degree.
On average, the world has one earthquake of magnitude eight per year, although there are also years in which this type of tremors are two or three, says the seismologist Tillman. Ninth degree tremors are much rarer – the last of its kind was in 2011 in Japan, in the Tohoku region. The subsequent tsunami, which also damaged the nuclear plant in Fukushima, caused particularly great damage. Over 22,000 people died.
Can earthquakes be predicted?
The professor from Potsdam explains to ZDF that a distinction must be made between prediction and forecast. The first term describes a very accurate prediction of an earthquake with details of the time of occurrence, location and intensity, the second term describes a probability based on external circumstances, for example the frequency of smaller tremors.
And while the “prediction” of earthquakes is impossible, predictions can be made, Tillman says. And the fact that Japan has pre-emptively warned about the possibility of a “mega-earthquake” may also be justified by historical observations, he believes. “The earthquake in the Tohoku region had a strong foreshock. And probably in addition to this, the warning has now been given that after a major earthquake in the Nankai valley, a “mega-earthquake“ may occur.
Which regions besides Japan are particularly vulnerable?
„Earthquakes with a magnitude of nine only occur on huge structural faults where one plate slides under another,” Frederik Tillmann explains to ZDF. Most of these areas are at the edges between oceans and continents – for example along the Pacific Ring of Fire in Japan or in the Andes region. However, there are similar structures under the Himalayas.
At the same time, Tillman warns that the possible consequences of an earthquake do not depend only on magnitude. “And an earthquake of the seventh degree can be extremely deadly if, for example, it happens in the immediate vicinity of a city where the buildings are not sufficiently protected against tremors“, says the seismologist.
Could Europe be affected by a “mega-earthquake”?
In Europe, stronger earthquakes are most likely in Italy, Greece and Turkey. The two earthquakes in Turkey on February 6, 2023, in which more than 50,000 people died during the tremors or from their consequences, were, for example, of magnitude 7.7 and 7.6 - recalls ZDF. And in Germany, tremors of the third, fourth and fifth degree are very rarely observed – although stronger earthquakes are not excluded in principle.
Where would the consequences be particularly catastrophic?
„The poorer the country and the greater the corruption, the more severe the potential consequences of earthquakes would be,” explains Tillman, pointing out that the answer to this question is complicated – it depends on how earthquake risks are approached in the respective countries.
„Italy, for example, is a country that has financial opportunities and is aware of the threat of earthquakes,” says the expert. “However, there are constant earthquakes with severe consequences, as there are many old buildings there, which are extremely expensive to modernize.“ According to Tillman, a magnitude eight earthquake inland could be more dangerous than a magnitude nine earthquake on the coast – depending on how prepared the country is for a tsunami and how much time it has for evacuation.
ZDF recalls that the deadliest earthquake of this millennium was of a relatively small magnitude of the seventh degree. It hit Haiti on January 12, 2010 and devastated the capital Port-au-Prince. The death toll reached 316,000.
How can it be countered?
According to seismologist Tillman, quoted by ZDF, there are mainly two effective countermeasures. The first of them is the construction of well-fortified buildings – if there are relevant building codes that are controlled and observed. The second important measure is the tsunami warning system. “People should know in advance how they should behave and how to quickly leave the coastal region.“
As indicated by the data of Japanese media, the warning of the local authorities definitely played a serious role in increasing the sensitivity and preparedness of the population. Because Japan is periodically affected by various natural disasters – earthquakes, typhoons and torrential rains, it is logical that disaster prevention occupies an important place, writes the “Sumikai“ site.
Good preparation is important
For this purpose, a number of institutions in the country are constantly developing new ideas for better preparation and response to disasters. But a central factor in protecting against them is the civilian population itself – only if it takes the dangers seriously and implements protective measures can lives be saved and damage reduced. As indicated by the data of an up-to-date survey – over 80 percent of the population on the southern coast of the country, for whom the warning of a "mega-earthquake" was valid, took it seriously. And 50 percent stated that they had undertaken preparations in case of an earthquake.