Volcanic crises are often associated with magmatic intrusions or pressurization of magma chambers of various shapes. These volumetric sources deform the country rocks, changing their density, and cause uplift. Both the net mass of intruding magmatic fluids and these deformation effects contribute to surface gravity changes. Thus, to estimate the intrusion mass from gravity changes the deformation effects must be accounted for. We develop analytical solutions and computer codes for the gravity changes caused by triaxial sources of expansion. This establishes coupled solutions for joint inversions of deformation and gravity changes. Such inversions can constrain both the intrusion mass and the deformation source parameters more accurately.
Simulating magma propagation pathways requires both a well-calibrated model for the stress state of the volcano and models for dike advance within such a stress field. With the purpose of establishing a framework for calculating computationally efficient and flexible shallow magma propagation scenarios, we develop three-dimensional models for the stress state of volcanoes with complex topographies and edifice histories as well as a new simplified three-dimensional model of dike propagation using the stress state of the volcano as input. Next, we combine all these models to calculate shallow dike propagation scenarios for complex caldera settings. The resulting synthetic magma pathways and eruptive vent locations broadly reproduce the variability observed in natural calderas.
Volcanism in continental rifts is generally observed to shift over time from the inside of the basin to its flanks and conversely, but the controls on these switches are still unclear. Here we use numerical simulations of dike propagation to test the hypothesis that the spatio-temporal evolution of rift volcanism is controlled by the crustal stresses produced during the development of the rift basin. We find that the progressive deepening of a rift is accompanied by a developing stress barrier under the basin, which deflects ascending dikes, causing an early shift of volcanism from the inside to the flanks. The intensification of the barrier due to further deepening of the basin promotes the formation of lower crustal sill-like structures that can stack under the rift, shallowing the depth of magma injection, eventually causing a late stage of in-rift axial volcanism.
Assessing volcanic hazard in regions of distributed volcanism is challenging because of the uncertain location of future vents. A statistical-mechanical strategy to forecast future vent locations was recently proposed. Here we further develop and test that strategy with analog models. We stress a gelatin block in controlled conditions and observe air-filled crack trajectories. We use the observed surface arrivals to sample the distributions of parameters describing the stress state of the gelatin block, combining deterministic crack trajectory simulations with a Monte Carlo approach. We find the algorithm retrieves the stress imposed on the gelatin and successfully forecasts the arrival points of subsequent cracks in the same experimental setups. We discuss how the approach may be used to gain insight on the stress state of regions of distributed volcanism.