Episode notes
16 Feb 2026
Scientists drilled into the subduction zone off the coast of Japan to investigate the cause of the devastating 2011 tsunami. They discovered a layer of pelagic clay, which may explain why the earthquake rupture travelled so shallowly, displacing a large amount of water and generating the massive tsunami. This finding could improve tsunami prediction for regions like the Pacific Ring of Fire.
The 2011 Japan earthquake caused a devastating tsunami due to a unique geological feature: a 328ft thick layer of soft, slippery pelagic clay. This clay layer acted as a lubricant, allowing tectonic forces to slip easily and lift the ocean floor by 131-200ft, generating a massive tsunami. The discovery of this weak layer raises concerns about the potential for similar shallow, tsunami-generating ruptures in other subduction zones worldwide.