The Recent Aspects of Volcanic and Seismic Activity in Japan
Toshiyasu Nagao, Director of Earthquake Prediction Research Center, Tokai University
by Toshiyasu Nagao
The characteristics of the Japanese archipelago and its volcanoes
Japan is the only major economic power in the world prone to both volcanic and seismic activities. Home to only 0.25% of the world’s land area, Japan has 7% of the world’s active volcanoes. Moreover, about 10% of all earthquakes occur in and around Japan. These are the reasons why Japan is very scenic and has many hot springs.
One should consider the volcanic and seismic activity during the twentieth century, particularly during the postwar high growth period, as extremely low. In contrast, in the second half of the current century we will see a number of volcanoes erupting every year. The catalyst of this change was clearly the 2011 Great East Japan Earthquake, which completely changed Japan’s subterranean condition. Many researchers believe that the current seismic activity signals a return to Japan’s original state. In the next ten years, there will be a number of volcanic eruptions of significant scale.
The effect of the 2011 Earthquake could last for decades
The 2011 Great East Japan Earthquake had a great effect on Japan’s crust. The crust of the Japanese Archipelago is complexly interlaced like a jigsaw puzzle, so even if just the Tohoku region is displaced, it is wrong to think things end there. In the near future, it is likely that there will be a magnitude 8 earthquake accompanied by a 10 meter tsunami in the sea region off Aomori and the Boso-Oki Peninsula, an area that was not destroyed by the 2011 disaster.
It is also likely that there will be an “Outer-Rise” earthquake on the east side of the Japan Trench, the same area of origin as the 2011 earthquake. This earthquake will be accompanied by a 10-meter tsunami. In fact, just as the 1896 Meiji Sanriku Earthquake caused the 1933 outer-rise Showa Sanriku Earthquake, the effects of great earthquakes last not just years, but decades. We should live under the assumption that there will likely be a large-scale earthquake in the Tokyo area or the Nankai Trough of Southeast Japan.
Current geological conditions resemble 9th century Japan
We are currently living in an extremely active period of volcanic and seismic activity. In addition, many researchers believe that Japan’s current geological condition resembles that of the ninth century.
Let’s do a quick review of the events of the ninth century. Mt Fuji erupted in 864. Five years later,in 869, the Great Jogan Earthquake struck Japan. This earthquake is considered to be the previous Great East Japan Earthquake. It has also been revealed that there was a huge tsunami that surged inland in 869 just as there was in 2011. Nine years later, in 878, a huge earthquake occurred in the Kanto area. This was followed by another earthquake in 887.
As I mentioned earlier, it seems possible that after 1100 years the Japanese Archipelago has re-entered a period of extreme seismic activity.
If we assume that Japan’s current condition is like that of the ninth century and we calculate 2011+9=2020, then we arrive at the possibility that Japan will be visited by a large earthquake at exactly the same time as the 2020 Olympics. Hypothetically, if there was a large earthquake in the Tokyo area in 2019, then it would become necessary to put effort into reconstruction rather than hosting the Olympic Games. It seems that these types of hypotheses will be an important topic of discussion for the Japanese government and the city of Tokyo.
New progress in earthquake prediction
Following the Great East Japan Earthquake, the field of earthquake prediction was subject to strong criticism. However, recently there have been big changes occurring in this field. In general, I think most people believe earthquake prediction is the work of seismologists, but in fact short-term predictions are a part of “Physics of Brittle Fracture” or “Statistical Physics.” A seismologist’s primary tool of measurement is the seismograph, but the seismograph is an observation tool that only moves after an earthquake has started. In order to make short-term predictions, it is necessary to have an observation tool that moves before an earthquake occurs.
Great progress is being made in earthquake prediction research around the world. Researchers agree that seismological and geodetic methods are effective for long- and mid-term prediction (one year to several decades in the future), and that electromagnetic methods (including satellite observation) and geochemial methods (including groundwater level changes) are promising for short-term prediction (several months to several hours prior to an earthquake).
Even in the realm of seismology, applying statistical analysis to observations such as shifts in earthquake activity patterns is producing results. At the Tokai University Earthquake Prediction Research Center where I work, we have discovered a new algorithm for monitoring earthquake activity named the “down-under meteorological map.” This is an easy to understand, weather report-like visualization that shows seismic activity. In order to forecast the weather, it is necessary to understand the current general weather outlook, including atmospheric pressure, etc. Similarly, in order to predict seismic activity or volcanic eruptions it is also necessary to first understand what is currently happening under the earth’s surface.
Following the 1995 Great Hanshin Earthquake, Japan constructed the world’s most advanced observation network, making it possible to catch even incredibly small seismic activity. The down-under meteorological map presents those seismicity changes in a way that is easy to understand.
Southeast Asia and South America also experience a lot of earthquakes and volcanic eruptions, but many of the countries in these regions do not have sufficient observation networks due to a lack of researchers and funds. From this point of view, I think that Japan should utilize its unique position as the country with the highest potential to contribute to observation activities by creating a “Pacific Rim Earthquake and Volcano Monitoring Organization.”
Toshiyasu Nagao is a professor of Geophysics and the Director of Earthquake Prediction Research Center in Tokai University.
(translation: Megan Dick)
Originally published at ignition.co.
