Imaging the internal workings of Axial Seamount on the Juan de Fuca Ridge.

Understanding the internal dynamics of volcanoes has been a long-standing goal of earth sciences, with much progress made over the past several decades. During this time, the systematic monitoring of a volcano was best done subaerially (e.g., Hawaii), while detailed imaging of magma chamber structure using seismic reflection and refraction surveys was best done in a marine setting (e.g., East Pacific Rise)-but not in the same place. Recent advances could break this mismatch: (1) Mapping and monitoring techniques have been adapted to the marine environment and applied at Axial Seamount, which is now monitored in real-time through the OOI Observatory; (2) Improved seismic acquisition technologies and imaging techniques now make it possible to image, in unprecedented detail, complex magma chamber structure and fluid pathways/fractures in the oceanic crust. In combination, these breakthroughs represent an unprecedented opportunity to make a transformative jump in our understanding of the internal workings of Axial Seamount specifically and, more generally, of volcanoes worldwide.

In this presentation, we will review observations of key structures imaged on existing 2D seismic transects using state-of-the-art wavefield-based imaging techniques. We will also present preliminary results from a recently acquired 3-D seismic survey over the volcanic edifice (the NSF-funded AXIAL 3D expedition, MGL1905). These structures include two elongated shallow magma reservoirs overlying a narrower feeding conduit of vertically stacked melt lenses; a subsiding caldera and a network of fractures, uniquely imaged here, that might facilitate transport of magmatic and hydrothermal fluids and help relieve stress buildup within the volcanic edifice.