How often do megathrust earthquakes occur?
The recurrence time varies from subduction zone to subduction zone. In the Cascadia subduction zone 13 megathrust events have been identified in the last 6000 years, an average one every 500 to 600 years. However, they have not happened regularly. Some have been as close together as 200 years and some have been as far apart as 800 years. The last one was 300 years ago.
