Recent research has revealed that a significant section of the Kuril Trench off the coast of Hokkaido is accumulating strain to a concerning degree. This area, where the oceanic and continental plates are strongly locked together, could potentially generate a magnitude 9-class earthquake, similar to past megathrust quakes.
A research team comprising Tohoku University, Hokkaido University, and the Japan Agency for Marine-Earth Science and Technology (JAMSTEC) has been conducting seafloor crustal movement observations since 2019. Their findings indicate that the boundary between the oceanic and continental plates has an area of intense locking, where strain is continuously accumulating. Given that the last massive earthquake along this trench occurred in the 17th century, roughly 400 years ago, experts are urging people to be prepared for potential tremors and tsunamis.
According to Japan’s Earthquake Research Committee, the probability of a magnitude 8.8 or greater earthquake occurring in this region within the next 30 years is estimated to be between 7% and 40%. This underscores the need for continuous monitoring and disaster preparedness.
Seafloor GPS Observations Confirm Strain Accumulation
Since 2019, the research group has been utilizing seabed GPS observation points to measure the movement of the tectonic plates along the Kuril Trench. The results indicate that the oceanic plate is shifting approximately 8 cm per year toward the continent. At the same time, GPS points placed on the continental plate near the subduction zone are also moving at a similar rate, confirming the presence of a strongly locked zone where strain is building up.
If the same rate of plate locking has continued over the past 400 years, the accumulated strain could now be equivalent to the amount of movement that occurred during the last megaquake in the 17th century. This suggests that the potential for a large-scale seismic event is increasing.
The Potential for a Megaquake and Tsunami
The Kuril Trench has been known to generate large tsunamis in the past. Tsunami sediment research suggests that the 17th-century earthquake triggered significant coastal flooding. If a similar event were to occur today, it could lead to devastating tsunamis along the coasts of Hokkaido and beyond.
In comparison to past observations conducted only on land, seabed GPS technology now allows for a more precise understanding of how strain accumulates in the offshore region near the trench axis. If the locked section of the plate boundary suddenly slips, it could generate a tsunami similar to the one caused by the 2011 Tohoku earthquake.
Future Research and Disaster Preparedness
To gain a more detailed understanding of tectonic movements, the research team plans to expand its observation network to include the offshore area near Tokachi, Hokkaido. By continuing these observations, scientists aim to improve earthquake prediction models and enhance early warning systems.
Assistant Professor Fumiaki Tomita from Tohoku University’s International Research Institute of Disaster Science emphasized the importance of preparedness: "As we approach the 14th anniversary of the 2011 Great East Japan Earthquake, memories of that disaster are fading. However, we must remain aware that a similar event could occur in the future and take necessary precautions."
With growing evidence of strain accumulation along the Kuril Trench, experts stress the need for vigilance. Residents of Hokkaido and surrounding areas are advised to stay informed and be prepared for potential seismic activity and tsunamis.
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