Japan’s First-Ever Megaquake Warning Follows 7.1-Magnitude Tremor
In the wake of a powerful 7.1-magnitude earthquake that struck southern Japan on Thursday, August 8, the Japan Meteorological Agency has issued its first-ever “megaquake advisory.” This unprecedented alert has heightened concerns about the potential for a significant seismic event along the Nankai Trough, a notorious subduction zone along Japan’s southwest Pacific coast.
What the megaquake advisory entails
The advisory warns that the likelihood of strong shaking and large tsunamis is currently higher than normal along the Nankai Trough. This subduction zone, where tectonic plates collide and one slides beneath the other, is a known hotspot for seismic activity. However, the advisory does not guarantee that a major earthquake will occur within a specific timeframe.
Understanding the Nankai Trough
The Nankai Trough, an underwater subduction zone stretching nearly 900 kilometers, is where the Eurasian Plate meets the Philippine Sea Plate. The latter is being forced under the former, building up tectonic stress that can potentially unleash a “megaquake” with a magnitude exceeding 8. Historically, the trough has produced large earthquakes approximately every 100 to 150 years. These seismic events often occur in pairs, with the second quake typically following within two years. The last such pair of earthquakes struck in 1944 and 1946.
Thursday’s 7.1-magnitude earthquake occurred in close proximity to the Nankai Trough, raising fears that a larger, more devastating quake could follow.
When could the next megaquake strike?
Japan’s Earthquake Research Committee has estimated a 70% probability that a magnitude 8-9 megaquake will hit the Nankai Trough within the next 30 years. Such an event could send tremors from central Shizuoka, approximately 150 kilometers south of Tokyo, to southwestern Miyazaki. The potential consequences are dire: tsunami waves as high as 98 feet could reach Japan’s Pacific coasts within minutes of the quake.
A government report from 2013 estimated that a major earthquake along the Nankai Trough could affect a third of Japan’s territory, impacting nearly half of the country’s population of over 120 million. The economic damage could exceed $1.5 trillion, accounting for more than a third of Japan’s annual GDP.
Can earthquakes be predicted?
Despite advances in technology, accurately predicting earthquakes remains elusive. Effective prediction would require a precursory signal from within the Earth that consistently indicates an impending large quake. Currently, no equipment exists that can reliably detect such signals, making earthquake prediction an ongoing challenge for scientists.
Japan’s megaquake advisory serves as a stark reminder of the nation’s vulnerability to seismic events and underscores the importance of preparedness in the face of natural disasters.
