Anticipating abrupt shifts in temporal evolution of probability of eruption

International audience; Estimating the probability of eruption by jointly accounting for different sources of monitoring parameters overtime is a key component for volcano risk management. In the present study, we are interested in the transition froma state of low-to-moderate probability value and to the one of high probability value: the latter value generallysupports the call for evacuation. By using the data of MESIMEX exercise at the Vesuvius volcano, we investigatedthe potential for time-varying indicators related to the correlation structure or to the variability of the probabilitytime series for detecting in advance this critical transition. We found that changes in the power spectra and inthe standard deviation estimated over a rolling time window both present an abrupt increase, which marks theapproaching shift. Our numerical experiments revealed that the transition from an eruption probability of 10-15%to >70% could be identified up 3 hours in advance. This additional lead time could be useful to place different keyservices (e.g., emergency services for vulnerable groups, commandeering additional transportation means, etc.) ona higher level of alert before the actual call for evacuation.