Stress Inversion in a Gelatin Box: Testing Eruptive Vent Location Forecasts With Analog Models.

Assessing volcanic hazard in regions of distributed volcanism is challenging because of the uncertain location of future vents. A statistical‐mechanical strategy to forecast such locations was recently proposed: here, we further develop and test it with analog models. We stress a gelatin block laterally and with surface excavations, 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. While the individual stress parameters remain unconstrained, we effectively retrieve their ratio and successfully forecast the arrival points of subsequent cracks. Plain Language Summary: In regions of distributed volcanism, eruption locations (vents) are scattered over a large area. Forecasting the new eruption locations over such regions is critically important, as many are densely populated. One of the main difficulties is dealing with few known past eruptions, that is, the data available to constrain forecast models are scarce. Thus, we develop a forecast strategy by applying extension or compression to blocks of gelatin with surface excavations and observing the propagation of air‐filled cracks. Such models, if properly scaled, are an analog for magma propagation in the Earth's crust. We use the surface arrival points of some observed cracks to retrieve the statistical distributions of a few parameters controlling the stress field. Next, we use such distributions to forecast the arrival points of other observed cracks. Although we could not retrieve all the stress parameters accurately, the forecasts we perform are reliable. Our strategy may help retrieving the state of stress in volcanic regions and forecast the location of future vents. Key Points: We stress a gelatin block by excavating its surface and imposing lateral strain, then observe air‐filled cracks trajectoriesWe numerically simulate the trajectories and retrieve the stress state of the gelatin, then we forecast new crack arrivals at the surfaceOur strategy correctly retrieves the ratio between lateral extension and excavation depth and leads to effective forecasts of eruptive vents [ABSTRACT FROM AUTHOR]