Overview
- The study published in Science Advances on Saturday uses data from the CASIE21 oceanographic campaign to show the northern Cascadia subduction slab is fragmenting rather than failing in a single event.
- Researchers aboard the R/V Marcus G. Langseth used high-resolution seismic-reflection imaging and regional earthquake records to produce a detailed view of the slab and its faults.
- The team mapped an approximately 75-kilometre discontinuity near Vancouver Island with about a 5-kilometre vertical drop in the slab, and lead author Brandon Shuck says that section is close to detaching but not yet fully separated.
- The seismic record shows some segments remain active while detached pieces enter 'seismic silence,' a process that can create microplates and will change how seismic waves travel through the region.
- Because the tearing unfolds over millions of years, the discovery does not lower the short-term risk of megathrust earthquakes or tsunamis, but the new imaging gives scientists data to refine hazard and wave-propagation models and to guide follow-up mapping.