Months-long thousand-kilometre-scale wobbling before great subduction earthquakes.

Megathrust earthquakes are responsible for some of the most devastating natural disasters. To better understand the physical mechanisms of earthquake generation, subduction zones worldwide are continuously monitored with geophysical instrumentation. One key strategy is to install stations that record signals from Global Navigation Satellite Systems (GNSS), enabling us to track the non-steady surface motion of the subducting and overriding plates before, during and after the largest events.