Abstract
Volcano-tectonic seismicity and ground movement are the most reliable precursors to eruptions after extended intervals of repose, as well as to flank eruptions from frequently-active volcanoes. Their behavior is consistent with elastic-brittle failure of the crust before a new pathway is opened to allow magma ascent. A modified physical model shows that precursory time series are governed by a parent relation between faulting and elastic deformation in extension, subject to independent constraints on the rate of crustal loading with time. The results yield deterministic criteria that can be incorporated into existing operational procedures for evaluating the probability of crustal failure and, hence, levels of alert during an emergency. They also suggest that the popular Failure Forecasting Method for forecasting eruptions is a particular form of the parent elastic-brittle model, and that magma transport and crustal fracturing during unrest tend towards conditions for minimizing rates of energy loss.
Highlights
Most of the world’s active volcanoes are not regularly monitored (Tilling, 1995; Sparks et al, 2012), especially those that have been in repose for centuries or more
We argue that the precursory time series are governed by a deterministic parent relation between seismicity and deformation, subject to independent constraints on how the crust is loaded with time
Exploring the interactions has generated an independent class of fracture models, most of which have focused on strong interactions immediately before bulk failure (Main, 1996, 2000; Molchan et al, 1997; Guarino et al, 1998; Amitrano et al, 2005; Girard et al, 2010)
Summary
Most of the world’s active volcanoes are not regularly monitored (Tilling, 1995; Sparks et al, 2012), especially those that have been in repose for centuries or more. When such volcanoes reawaken, short-term forecasts of eruption are normally based on data from rudimentary monitoring networks installed after the start of unrest. Because the parent relation is generic, it can be applied in the absence of information about previous unrest and offers the prospect of enhancing the reliability of forecasts by integrating deterministic estimates of eruption time with existing probabilistic evaluations. The physical basis for the parent relation is reviewed and updated, before it is used to propose new operational procedures for emergency forecasts of eruptions
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