Japan, one of the most earthquake-prone countries on Earth, issued its first-ever "warning of a possible mega-earthquake" last week. This followed a powerful 7.1 magnitude earthquake that struck off the southeastern coast of the southern main island of Kyushu.
While the quake caused no casualties or significant damage, the warning triggered widespread fear and concern among the population, especially given experts' warnings that a 9.1 magnitude earthquake in the Nankai Trough could trigger a deadly tsunami within minutes.
The Japan Meteorological Agency (JMA) concluded that the August 8 earthquake, which occurred at the western edge of the Nankai Trough, increased the likelihood of another large earthquake. There is a 70-80% probability of an 8 or 9 magnitude earthquake associated with the Nankai Trough within the next 30 years, and this probability is now "higher than normal" after the recent earthquake, according to the JMA.
The Nankai Trough is an underwater trench that stretches from Hyuganada, in the waters off the southeastern coast of Kyushu, to Suruga Bay in central Japan. It extends for about 800 kilometers along the Pacific coast. The Philippine Sea plate there is slowly pulling the Eurasian plate downward and causing it to periodically snap back, which can result in a mega-earthquake and tsunami, the JMA explained. The last Nankai Trough earthquake off Shikoku in 1946 had a preliminary magnitude of 8.0 and killed over 1,300 people.
As early as 2013, a government disaster prevention panel said a 9.1 magnitude earthquake in the Nankai Trough could trigger a tsunami over 10 meters high within minutes, killing up to 323,000 people, destroying more than 2 million buildings, and causing over $1.5 trillion in economic damage to large swaths of Japan's Pacific coast.
However, experts have not yet detected any anomalous seismic or tectonic activity that would indicate an imminent mega-earthquake.
Blogs
