WHAT CAN SUBDUCTION MARGIN LAND- AND SEA-SCAPES TELL US ABOUT THE SYSTEM’S PROCESSES AND ENERGY BUDGET?

The various manifestations of subduction zone topography reveal the interplay of surface, magmatic and deformation processes within subduction zones. While all subduction margins have uplifted mountains and transport sediment to the ocean floor, the patterns of sediment transport, uplift and erosion vary significantly. For example, the expression of deformation within an accretionary wedge at the trench depends on sufficient sediment delivery to the ocean floor. Additionally, the trapping of sediment within the forearc basin depends on subsurface deformation processes to produce basin subsidence.

Deformation and sediment transport processes respond to both punctuated and continuous events over repeated earthquake and eruption cycles to create long-term records of topography and mass fluxes within subduction zones. Consequently, the long term erosion and sedimentation record contains fingerprints of large short duration earthquakes, but they must be found among the dominant signals of inter-event processes. In contrast, very large volcanic eruptions and landslide events may perturb the system and obliterate the more subtle records of inter-event erosion and sedimentation.

A variety of assumptions and lack of constraints limit our understanding of processes at the full range of time scales required to understand the interplay of deformation, magmatic and surface processes. For example, constraints on the contribution of distributed plasticity in the accretionary wedge could better inform how topography is built and eroded in the interseismic part of earthquake cycles.

The landscape and deformation energy budget serves as a framework for investigating the relationships between processes that act across a wide range of temporal and spatial scales. Use of this framework can map how findings from individual studies can impact our understanding of the whole subduction system. The deformation budget for subduction zone systems includes energetic input and sinks. Mass flux within the land- and seascape and associated changes in system deformation highlight the interdependence of surface, magmatic and faulting processes. Future transformative insights may arise from considerations of how topographic and deformational energy is budgeted during punctuated large events and within inter-event periods.