The subsurface beneath volcanoes typically hosts a complex architecture of magma-bearing features and faults. Triggering interactions between these structures, where they are observable, have been implicated in the initiation of eruptive or intrusive sequences. In this thesis, I present several case studies demonstrating the ubiquity of long-range or system-wide interactions between these features and the role of these interactions in contributing to volcanic processes. In Chapter 2, I analyze a seismic swarm at mantle depths beneath Pahala, Hawai‘i and identify it as the manifestation of magma propagation through a sill network. Structural connections between the sill complex and surface volcanoes, coupled with observations of correlated dynamics in the mantle and at the surface, indicate that eruptive dynamics at Kilauea may be informed over short timescales by processes occurring within a complex, laterally distributed magma system that extends to mantle depths. In Chapter 3, I calculate moment tensors for earthquakes in the Pahala Sill Complex and show that their source mechanisms reflect fluid propagation in a flexurally induced stress field. The mechanism of seismogenesis in the sill complex suggests that a feedback loop between permeability-increasing ruptures and continuing magma propagation could serve as a mechanism that enables surges in magma supply to the surface. In Chapter 4, I study seismicity and deformation measurements at Mauna Loa’s summit spanning the ten years leading up to its 2022 eruption. I show that the patterns of seismicity and deformation at the summit can be explained as the result of stress interactions between a magma chamber expanding in volume and a receiver fault plane in the volcano’s northwest flank. In Chapter 5, I demonstrate that stress-based volcanotectonic interactions propagated over long distances during the 2025 intrusive sequence at the Christiana-Santorini-Kolumbo volcano complex in the Aegean Sea. The results suggest that a collection of sufficiently densely emplaced critically stressed magmatic and tectonic features can sustain volcanotectonic activity over distances far longer than the lengthscale of any individual feature. I additionally present preliminary results identifying correlations in seismic activity between Hawaiian volcanoes that are spaced over 100 km apart. Together, the results presented in this work present a framework for identifying the structures and processes underlying the initiation and sustenance of volcanotectonic unrest.
John D. Wilding (Tue,) studied this question.