Ancient Clay Layer, 20 Million Years Old, Identified as Cause of 2011 Megaquake.

Scientists Uncover the Trigger for the 2011 Megaquake

According to TSN.ua: A groundbreaking research mission to the Japan Trench has pinpointed the cause of the devastating 2011 earthquake, which triggered a catastrophic tsunami and the Fukushima Daiichi nuclear disaster. In 2024, a team of geologists aboard the drilling vessel Chikyu set a Guinness World Record for the deepest scientific ocean drilling to reach this conclusion.

Core samples retrieved during the expedition revealed that the fault rupture occurred within a 25–30 meter layer of ancient clay. This clay formed roughly 20 million years ago from sediments that had accumulated on the ocean floor over an astonishing 130 million years. The tectonic plates in the region slipped by 50–70 meters along this weak layer, which was the primary mechanism behind the massive quake. This discovery provides crucial physical evidence from the actual fault zone, a rare and significant achievement in seismology.

Implications for Understanding Major Earthquakes

Researchers now believe similar clay layers could explain other megaquakes, including the 2004 event off the coast of Sumatra. These findings could fundamentally reshape our understanding of seismic processes and risks in active subduction zones around the world.

The analyzed data may significantly impact how scientists assess seismic hazards in regions with comparable geological conditions. This knowledge could, in turn, aid in refining early warning systems and mitigating risks associated with natural disasters. The research results may also form the foundation for new scientific studies focused on analyzing clay layers and their critical role in seismic activity.