Off the coast of British Columbia, Washington, Oregon, and Northern California, lies one of the world’s greatest impending earthquake hazards: The Cascadia Subduction Zone. While scientists have long known that Cascadia is capable of producing powerful earthquakes, there has been far less certainty about how much of the shallow part of the fault is locked and accumulating strain. 

In a recent study titled “Near full locking on the shallow megathrust of the central Cascadia subduction zone revealed by GNSS-Acoustic,” Cascadia CoPes Hub researcher David A. Schmidt and colleagues used global navigation satellite system-acoustic (GNNS-A) technology to make the first direct measurements of horizontal movement on the seafloor along the central Cascadia margin. 

Reporting from an array of GNNS-A sites, their observations revealed that the shallow megathrust is primarily locked offshore of central Cascadia. This discovery suggests that a future earthquake has the potential to rupture along the shallow subduction zone interface. Such a rupture could cause increased tsunami risk due to the uplift of the seafloor or due to the greater ground shaking which would cause a submarine slope failure. 

These results highlight the importance of updating earthquake and tsunami hazard models to reflect the potential for shallow fault rupture. Including this data will help improve preparedness and risk mitigation for communities throughout the Pacific Northwest. To learn more click here.