Transit Cruise

Alaska GNSS-A 2024

Deformation of the seafloor is an important tectonic process, which can best be studied with marine geodetic techniques. The GNSS-Acoustic method is the technique chosen by a community workshop to investigate the following processes in Cascadia and Alaska: 1. Along-strike changes in coupling and relation to onshore deformation. A strong and widely spaced geodetic backbone offshore of existing on-land geodetic infrastructure, in regions not constrained by land stations could serve as the greatest return on investment for scientific and hazards understanding of megathrust subduction behavior. 2. Near-trench coupling and relation to tsunami earthquake(s) and down-dip behavior. While Alaska is the only of the two locales that has the known occurrence of a damaging tsunami earthquake (characterized by its outsized tsunami wave amplitude for earthquake magnitude) in 1946, it is understood that due to depth restrictions particularly in the 1946 rupture patch, much more of the near-trench environment off Cascadia can be evaluated using current instrument pool transponders. 3. Occurrence of shallow aseismic slip and its relation to earthquakes. The Cascadia subduction zone has clearly observable and large down-dip slow slip events, and an overall large near-trench exposure capable of observation with the geodetic instrument pool. 4. Postseismic time-dependent variations in coupling, including transients, afterslip, viscous relaxation, and recoupling. This was viewed as much more important in Alaska where recent large earthquakes allow for much greater potential for capturing discernable time-dependent variations in coupling behavior.