Construction and subduction of the Louisville Ridge, SW Pacific—insights from wide-angle seismic data modelling

The Louisville Ridge is a ca. 4000 km-long chain of seamounts in the SW Pacific that is currently being subducted at the Tonga-Kermadec trench. The Pacific Plate, on which the chain sits, is subducting obliquely beneath the Indo-Australian Plate. Combined with the oblique strike of the chain relative to the margin, this results in the southward migration of the ridge-trench intersection and leads to significant along-trench variation in forearc morphology as a result of tectonic erosion processes. To understand how the subduction of such large-scale plate topography controls forearc deformation, knowledge of the structure of the seamounts themselves and the crust upon which they lie, and how these seamounts are deformed prior to and on entering the trench is required. The TOTAL (Tonga Thrust earthquake Asperity at Louisville Ridge) project aimed to address these questions by undertaking a multidisciplinary geophysical study of the ridge-trench intersection and surrounding region, as part of which multichannel and wide-angle seismic, gravity and swath bathymetry data were acquired along a ∼750 km-long profile extending along the Louisville Ridge and into the adjacent Tonga forearc.