On the Complex Topography of Marine Volcanoes and Its Control on the Spatial and Magnitude Distribution of Surface Displacement

Marine volcanoes exhibit significant topographic relief, as they extend from deep below sea level to thousands of meters above. These volcanoes often have complex, asymmetric topographies due to the submersion of their flanks, yet deformation models often approximate this topographic surface as flat and overlook its effect in modeling approaches. This limiting perspective may lead to inaccurate assessments of deformation sources and potential hazards. In this study, we investigate the effect of complete marine volcano topography on deformation modeling. We comprehensively characterize volcano shape by applying a geomorphometric parameterization of natural asymmetry and steepness to describe marine volcanoes. Then, by building upon an existing analytical solution for triangular dislocations, we account for complete edifice topography (from the submarine base to the subaerial peak) and discretized source geometries to be solved in a full-space modeling domain. We demonstrate that models with complex topographies deviate to a greater extent from flat surface models, resulting in significant underestimations of both magnitude (up to 18% and 57% for vertical and horizontal, respectively) and spatial distribution of resultant displacement. In addition, we show that geomorphometric parameterization can provide a first-order approximation of deviation from a model with no topography. In the case of island volcanoes, the resultant displacement field is not confined to the onshore area but can extend beyond the coastline to the submarine edifice. This is particularly important as technology advances and submarine monitoring becomes feasible. Our approach enhances our understanding of volcano deformation scenarios and provides a tool for optimizing GNSS network design.