An international team of geophysicists published on September 24, 2025 in the journal Science Advances the first clear images of a subduction zone in the midst of disappearing, off Vancouver Island, Canada. Using sound waves, the group reconstructed a 75-kilometer fracture that splits the Juan de Fuca plate.
The Juan de Fuca plate sinks slowly beneath the North American plate in the Cascadia subduction zone, one of the structures where the planet's largest-magnitude earthquakes and tsunamis occur. For Mexico the case is not foreign: Mexico's Pacific coast also rests on a subduction zone, where the Cocos plate slides beneath the North American plate, and the fossil microplates off Baja California are remnants of the ancient Farallon plate. The country concentrates much of its seismicity in that coastal strip. According to the Columbia Climate School, the study offers an explanation of how those fragments form: dying subduction zones disintegrate progressively.
The work is based on the CASIE21 campaign, carried out in 2021, which sent sound waves to the ocean floor and recorded them on a 15-kilometer hydrophone cable to reconstruct the hidden structures. The profiles also reveal a block that dropped nearly 5 kilometers. Seismic activity is uneven along the fracture: there are stretches with tremors and others unusually silent, which the authors interpret as segments that have already separated completely. Brandon Shuck, a geologist at Louisiana State University and lead author, told Investigación y Desarrollo: "This is the first time we have a clear image of a subduction zone in the midst of disappearing." On the mechanism, he described "a train slowly derailing, car by car."
The authors caution that the fragmentation occurs over millions of years and does not significantly change Cascadia's seismic risk in the short term: the region retains the capacity to produce large-magnitude earthquakes and tsunamis. The open question is whether a large rupture crosses those internal divisions or stops at them, a datum that feeds propagation models.
This article was written with the assistance of artificial intelligence from verified sources and reviewed by a human editor before publication.
