Anticipating the timing of major earthquakes and which fault segments present the greatest hazard has long been a challenge in subduction zone science. At the largest spatial scale, deformation throughout the subduction system is coupled in space and time, and novel geodetic and seismologic observations made possible by the emergence of offshore instrumentation is poised to help us unravel these connections. At the smallest spatial scale, deformation processes control how rocks respond to the boundary conditions, whether by faulting or distributed flow, and how faults slip, whether by seismogenic slip, aseismic creep, or intermediate behaviors.

Understanding these processes requires new laboratory experiments designed to determine the properties of complex rocks that experience complex histories and investigations of rocks exhumed from fossil systems to ground-truth these measurements and observations. Finally, relating the processes by which rocks deform locally to the spatial and temporal evolution of the system requires numerical models validated by structural images from active source seismic, MT, bathymetric data, and modern surface techniques (LiDAR, paleoseismology).

​

The SZ4D Faulting and Earthquakes Cycles Working Group focuses their effort around four central questions that define the limits of what we know about when, where, and why large earthquakes occur.