ALBERT

Description: The development of long-term hazard maps for pyroclastic density currents (PDC) at Campi Flegrei (CF) caldera is a challenging problem. The probability distributions for the spatial location of the next event producing a PDC, the size of the flow, and the temporal estimate for such an event in the future must be convolved to achieve the necessary assessments. This task is additionally complicated by the remarkable epistemic uncertainty on the eruptive record, affecting the time of past events, the location of vents as well as the PDCs areal extent estimates. As a consequence, with the aim of quantifying some of the main sources of uncertainty, we provided mean and percentile maps of PDC hazard levels. The hazard maps were produced combining a vent-opening probability map, statistical estimates concerning the eruptive scales and a Cox-type temporal model including self-excitement effects, based on the eruptive record of the last 15 ka. The results were obtained by using a Monte Carlo approach and adopting a simplified inundation model based on the “box model” integral approximation and tested with 2D transient numerical simulations of flow dynamics. Remarkable differences can be observed between the past activity in the eastern and western sectors of the caldera: the dependence between PDC scales and the caldera sector was implemented in the hazard maps. Conditional maps concerning PDC originating inside limited zones of the caldera, or PDC with a limited range of scales were also produced with the aim of providing hazard assessments for particular scenarios. Finally, the effect of assuming different time windows for the hazard estimates was explored, including also the possibility of the occurrence of multiple events in the same time window. The analysis allowed us to identify areas with elevated probabilities of flow invasion as a function of the time window considered.

Description: Published

Description: Puerto Varas (Chile)

Description: 6V. Pericolosità vulcanica e contributi alla stima del rischio

Description: We present two models using monitoring data in the production of volcanic eruption forecasts. The first model enhances the well-established failure forecast method introducing an SDE in its formulation. In particular, we developed new method for performing short-term eruption timing probability forecasts, when the eruption onset is well represented by a model of a significant rupture of materials. The method enhances the well-known failure forecast method equation. We allow random excursions from the classical solutions. This provides probabilistic forecasts instead of deterministic predictions, giving the user critical insight into a range of failure or eruption dates. Using the new method, we describe an assessment of failure time on present-day unrest signals at Campi Flegrei caldera (Italy) using either seismic count and ground deformation data. The new formulation enables the estimation on decade-long time windows of data, locally including the effects of variable dynamics. The second model establishes a simple method to update prior vent opening spatial maps. The prior reproduces the two-dimensional distribution of past vent distribution with a Gaussian Field. The likelihood relies on a one-dimensional variable characterizing the chance of material failure locally, based, for instance, on the horizontal ground deformation. In other terms, we introduce a new framework for performing short-term eruption spatial forecasts by assimilating monitoring signals into a prior (“background”) vent opening map. To describe the new approach, first we summarize the uncertainty affecting a vent opening map pdf of Campi Flegrei by defining an appropriate Gaussian random field that replicates it. Then we define a new interpolation method based on multiple points of central symmetry, and we apply it on discrete GPS data. Finally, we describe an application of the Bayes’ theorem that combines the prior vent opening map and the data-based likelihood product-wise. We provide examples based on either seismic count and interpolated ground deformation data collected in the Campi Flegrei volcanic area.

Description: Published

Description: San Francisco

Description: 6V. Pericolosità vulcanica e contributi alla stima del rischio

Description: The Campi Flegrei (CF) is an active volcanic area located in the Campanian Plain, along the Tyrrhenian margin of the Southern Appennines (Italy), dominated by the formation of a 12 km large, resurgent caldera. The nested Campi Flegrei caldera results from successive collapses related to the eruptions of the Campanian Ignimbrite (CI; 39.3±0.1 ka) and Neapolitan Yellow Tuffs (NYT; 14.9±0.4 ka). After the NYT eruption, volcanism was concentrated in three epochs of activity, alternating to periods of quiescence. The great majority of the eruptions have been explosive, variable in magnitude and also characterized by the generation of fallout, ash deposits and pyroclastic density currents (PDCs). We present here a methodology aimed at the construction of a probability map of PDC hazard of the CF area. At this stage, results are preliminary and will be improved by future research work. Nevertheless, first outcomes already provide numerous insights in the problem and contribute to define future research directions. In the study we had to cope with three different problems, related to different probability spaces: • constructing a probability map of the place of a new vent opening • giving a probability law to the area of invasion of a PDC from a fixed new vent • choosing a probability distribution for the uncertainty that affects the model itself To calculate the probabilistic simulations we used the R statistics software, and to plot the maps we used the ESRI platform.

Description: Published

Description: Vienna (Austria)

Description: 6V. Pericolosità vulcanica e contributi alla stima del rischio

Description: We present two models using precursory information in the production of volcanic eruption forecasts. The first model enhances the well-established failure forecast method introducing an SDE in its formulation. The second model establishes a simple method to update prior spatial maps. The prior reproduce the two-dimensional distribution of past activity with a Gaussian Field. The likelihood relies on a one-dimensional variable characterizing the chance of material failure locally, based on the horizontal ground deformation.

Description: Published

Description: Valencia

Description: 6V. Pericolosità vulcanica e contributi alla stima del rischio

Description: Lo studio Bevilacqua et al. (2017) ha ottenuto diversi risultati sulle stime di pericolosità da PDC: 1) la statistica della scala eruttiva negli ultimi 15 ka indica che in passato sia stata significativamente maggiore nel settore orientale della caldera (a est di E14°12'). Questo ha effetti significativi sulla pericolosità da PDC, con una riduzione ad ovest, ed un aumento ad est. Mappe basate su scenari fissi sono pure disponibili, ma rappresentano una semplificazione rispetto alle stime di pericolosità complete. Gli scenari a scale eruttive fissate possono infatti corrispondere ad eventi poco probabili. Il 95% della scala eruttiva è pari a ~39±11 km2 nel settore occidentale e ~169±18 km2 in quello orientale. Grazie allo studio Bevilacqua et al. (2016) sono disponibili delle stime temporali, basate sulla statistica del record passato. Le stime tengono conto degli effetti di clustering nei dati, che sono significativi. La frequenza eruttiva è diversa fra i due settori, con una maggiore frequenza nel settore orientale. L'interpretazione di Monte Nuovo con inizio di una epoca eruttiva ha effetti significativi sulla pericolosità da PDC a 10 anni, con una riduzione sostanziale nel caso contrario. Stime di pericolosità a 50 anni sono pure disponibili, anche considerando l'effetto di eruzioni multiple. Mappe che assumono il punto di origine del PDC in una specifica porzione della caldera sono disponibili. Esse costituiscono scenari con probabilità anche significativa. Le mappe localizzate permettono di testare rapidamente vincoli sulla posizione ottenibili coi dati di monitoraggio. Le stime sulla posizione della bocca eruttiva, i.e. il punto di origine dei PDC dovrebbero essere migliorate, includendo gli effetti di precursori sismici e deformazione. In particolare: 1) sono disponibili nuovi dati sulla storia della deformazione negli ultimi 15 ka che possono permettere di indagare maggiormente il legame fra deformazione e posizione delle bocche passate (i.e. Bevilacqua et al. 2017). 2) è in studio un meccanismo di aggiornamento short-term delle mappe in seguito all'osservazione di nuovi dati sismici, che combini: - un modello fisico sulla distanza fra epicentro e potenziale nuova bocca eruttiva, - la stima della probabilità che uno sciame sia un precursore eruttivo - la sensibilità delle stime rispetto alla memoria del sistema dei dati osservati in precedenza. 3) La portabilità ed il confronto delle mappe probabilistiche e dell'incertezza ad esse associata potrebbe essere aumentata, formalizzandone una rappresentazione comune tramite campi Gaussiani. Questo richiede uno studio ulteriore delle proprietà di correlazione spaziale fra punti diversi della caldera, e può facilitare la formulazione di un meccanismo robusto di aggiornamento short-term.

Description: Unpublished

Description: Napoli

Description: 6V. Pericolosità vulcanica e contributi alla stima del rischio