A simple two-state model interprets temporal modulations in eruptive activity and enhances multivolcano hazard quantification

Abstract

Volcanic activity typically switches between high-activity states with many eruptions and low-activity states with few or no eruptions. We present a simple two-regime physics-informed statistical model that allows interpreting temporal modulations in eruptive activity. The model enhances comprehension and comparison of different volcanic systems and enables homogeneous integration into multivolcano hazard assessments that account for potential changes in volcanic regimes. The model satisfactorily fits the eruptive history of the three active volcanoes in the Neapolitan area, Italy (Mt. Vesuvius, Campi Flegrei, and Ischia) which encompass a wide range of volcanic behaviors. We find that these volcanoes have appreciably different processes for triggering and ending high-activity periods connected to different dominant volcanic processes controlling their eruptive activity, with different characteristic times and activity rates (expressed as number of eruptions per time interval). Presently, all three volcanoes are judged to be in a low-activity state, with decreasing probability of eruptions for Mt. Vesuvius, Ischia, and Campi Flegrei, respectively.

Assessing long-term tephra fallout hazard in Southern Italy from Neapolitan volcanoes

“…Translated into the volcanic context, we implemented the PVHA related to a set S of volcanoes by calculating the mean annual frequency with which a certain hazardous phenomenon quantified by the intensity measure z (tephra load at the ground, in our case) exceeds the threshold Z at a geographical location x during a given exposure time window ∆T . Following Martinéz and Selva et al (2022), we quantify by:…”

“…Ischia has one eruption size class defined as Large, representing the Cretaio Tephra (ca. 60 CE; Orsi et al, 1992Orsi et al, , 1996 which is the largest explosive eruption that occurred in the last 3 kyr beside other 33 eruptions of lower intensity (de Vita et al, 2010;Selva et al, 2019Selva et al, , 2022Primerano et al, 2021). The parameters related to all eruption size classes are reported in A1.…”

“…Cornell, 1968). In volcanology, this is complicated by the fact that volcanic systems may be very different to each other and may experience different phases of activity, complicating the potential homogeneous integration of different volcanoes in the same hazard quantification (Selva et al, 2022). To this end, some studies applied methodologies to rank multiple volcanoes according to their hazards (e.g.…”

“…A breakthrough study in providing the estimation of the present state of the Neapolitan volcanoes has been proposed by Selva et al (2022) through the development of a simple physics-based statistical model that satisfactorily fits the eruptive history of all the Neapolitan volcanoes, accounting for potential changes in their eruptive regime. The model is compatible with existing data (including isolated events and long repose periods) and accounts for two activity regimes (high-low) able to describe the temporal modulations in eruptive activity.…”

“…In this work, by merging the model of Selva et al (2022) into the new PVHA workflow developed by Martinéz Montesinos et al ( 2022), we provide a prototypical methodology for long-term tephra fallout hazard assessment on a large-scale domain (Southern Italy) at 3 km resolution, combining the impacts of the three active Neapolitan volcanoes. Since the statistical evaluation of the fallout hazard requires to take into account a wide spectrum of different volcanic scenarios, we explored the intrinsic variability of the explosive eruptions performing a large number of numerical simulations of tephra dispersion from each volcano, considering the wind patterns over the last 30 years.…”