Understanding the processes controlling landslides, earthquakes, volcanic eruptions and tsunamis requires utilizing natural experiments and integrated models to identify and isolate controlling factors. Subduction zone hazards often occur as a
cascading series of events, requiring a system wide and integrative approach to understand. How do climate and tectonics interact to determine the susceptibility to landslides? What is the relative importance of magma supply and crustal faulting in controlling eruptive frequency? Are the size and location of earthquakes affected by structural boundaries? How do cascading sequences of events impact
subduction zone hazards? These and other geohazard questions can be addressed by studying behaviors across subduction zones. We invite contributions that use the power of comparison across multiple subduction zones to develop new insights. SZ4D is a community-driven initiative for a long-term, interdisciplinary research program to define the limits and possibilities of predicting geohazards. Observational, theoretical and laboratory studies comparing the SZ4D focus areas of Cascadia, Alaska and Chile are particularly welcome.