The chance of experiencing a megaquake along the Nankai Trough has alarmingly increased to approximately 80% within the next 30 years, according to Japan's government earthquake investigation panel. This recalculation, made every January, reflects the country's growing concerns about seismic activities after notable recent earthquakes.
Traditionally, the probability of such catastrophic events has swayed between 70% and 80% since 2018. Nevertheless, with new data emphasizing the reality of seismic activity, experts stress the need for sustained vigilance. Naoshi Hirata, the panel's chairman and professor emeritus at the University of Tokyo, pointedly noted, "It is difficult to predict when it might subside," indicating the uncertainty of the region's seismic future.
Japan's earthquake vulnerabilities have been underscored by the recent occurrence of M6.0-level quakes, including one on January 1, 2024, which have left the government and researchers concerned about the potential for larger tremors. Earlier this week, the Japan Meteorological Agency issued its second-ever Nankai Trough Extra Information following a magnitude 6.6 tremor noticed off the coast of Miyazaki Prefecture.
While this recent earthquake struck beneath the western edge of the predicted epicenter for a Nankai Trough megaquake, officials determined there was no immediate threat requiring special alerts. Earlier this month, the government had already issued advisories following another significant earthquake of magnitude 7.1, underscoring the urgency of monitoring seismic activities closely.
The Nankai Trough, located off Japan's Pacific coast, is notorious for its potential to produce major earthquakes, where the Eurasian and Philippine Sea tectonic plates meet. Japan has long braced for the consequences of such powerful earthquakes, with predictions outlining severe shaking and devastating tsunamis affecting vast coastal regions.
Looking back through history, the estimates for the likelihood of Nankai Trough megaquakes have seen significant hikes. Notably, the possibility was pegged at 60% to 70% back in 2013, rising to 70% by 2014, and then reaching its previous high of 70% to 80% just six years ago. The updated estimates indicate continuous exposure to quake-prone circumstances, as the committee notes this likelihood will only rise if no substantial quake occurs.
The recent temblor off the coast of Miyazaki, which measured at 6.6 on the Richter scale, was characterized as part of the region's seismic activity. The tremor hit at 9:19 p.m. local time and reached depths of about 36 kilometers. Reports from the Japan Meteorological Agency indicated areas experiencing intensity levels of 5 on its scale, compelling the agency to issue and later lift tsunami advisories after observing 20-centimeter waves.
These recent events have drawn the attention of experts like Yamashita Yusuke from Kyoto University, specializing in seismic activities around Nankai Trough. He stated, "The seismic energy released by Monday's quake was about half of the one (in August)," reassuring concerns over its immediate threat level. At the same time, Yamashita urged caution, acknowledging the tremor's proximity to high-risk areas where major quakes could strike. His insights underline how interconnected the current seismic events are with the historical precedent of larger strikes.
The Japan Meteorological Agency has actively encouraged citizens to remain alert, highlighting the possibility of future strong tremors as they analyze seismic trends intensively. Coverage surrounding the recent quakes emphasizes the pattern of unsettling activity leading many to ponder when the next significant quake will strike.
With the continually shifting tectonic plates and ever-present seismic energy, the question remains: Can Japan effectively prepare for and mitigate the aftermath of another devastating megaquake? For now, the need for preparedness and heightened awareness among residents is more important than ever, as agencies like the Japan Meteorological Agency continue to study these phenomena closely.