Volcanic hazard assessment at the restless Campi Flegrei caldera

Abstract

Eruption forecasting and hazard assessments at the restless Campi Flegrei caldera, within the Neapolitan volcanic area, have been performed using stratigraphical, volcanological, structural and petrological data.On the basis of the reconstructed variation of eruption magnitude through time, we hypothesize that the most probable maximum expected event is a medium-magnitude explosive eruption, fed by trachytic magma. Such an eruption could likely occur in the north-eastern sector of the caldera floor that is under a tensile stress regime, when the ongoing deformation will generate mechanical failure of the rocks. A vent could open also in the western sector, at the intersection of two fault systems contemporaneously activated, as happened in the last eruption at Monte Nuovo. The eruption could likely be preceded by precursors apparent to the population, such as ground deformation, seismicity and increase in gas emissions. It will probably alternate between magmatic and phreatomagmatic phases with the generation of tephra fallout, and dilute and turbulent pyroclastic currents. During and/or after the eruption, the re-mobilization of ash by likely heavy rains, could probably generate mud flows.In order to perform a zoning of the territory in relation to the expected volcanic hazards, we have constructed a comprehensive hazard map. On this map are delimited (I) areas of variable probability of opening of a new vent, (II) areas which could be affected by variable load of fallout deposits, and (III) areas over which pyroclastic currents could flow. The areas in which a vent could likely open have been defined on the basis of the dynamics of the ongoing deformation of the caldera floor. To construct the fallout hazard map we have used the frequency of deposition of fallout beds thicker than 10 cm, the frequency of load on the ground by tephra fallout and the direction of dispersal axes of the deposits of the last 5 ka, and the limit load of collapse for the variable types of roof construction. The pyroclastic-current hazard map is based on the areal distribution and frequency of pyroclastic-current deposits of the last 5 ka.

The Effects of Vent Location, Event Scale, and Time Forecasts on Pyroclastic Density Current Hazard Maps at Campi Flegrei Caldera (Italy)

“…The distribution of this variable is based on the record of the areas of the PDC deposits that occurred in the last 15 kyr. This dataset includes 47 events and largely relies on the work of Orsi et al (2004), with a few modifications and updates made in order to account for the most recent research findings. Epistemic uncertainty affects such record too: the error of deposit boundaries is considered to vary between ∼150 and ∼1,000 m, with a mean value of ∼500 m (see Bevilacqua, 2016).…”

“…Three epochs of activity in the last 15 kyr included at least 70 explosive eruptions alternated with periods of quiescence of several millennia (Rosi et al, 1983;Orsi et al, 2004). During this period, which is typically considered representative for hazard assessment studies, past eruptive vents opened in the central part of the caldera as well as at its boundaries, with individual events spanning a large range of eruptive scales including large explosive eruptions characterized by tephra volumes over 1 km 3 .…”

“…In the literature it is possible to find several studies aimed at solving the PDC hazard mapping problem in the CF area. For instance, first hazard maps of the zones potentially affected in the future have been produced by relying on the distribution of invaded areas by PDC associated with some of the main past events or specific eruptive scales (Lirer et al, 2001;Alberico et al, 2002;Orsi et al, 2004). A quantitative hazard map was constructed by using a dynamic flow model, with variable eruptive scales and uniform vent opening probability in an area centered on the town of Pozzuoli (Rossano et al, 2004).…”

Magma chamber evolution prior to the Campanian Ignimbrite and Neapolitan Yellow Tuff eruptions (Campi Flegrei, Italy)

“…The onset of Fig. 1 Geological and structural sketch map of the Southern Campanian Plain (modified after Orsi et al 2004) volcanism in the area is unknown. The oldest dated volcanic unit yielded an age of about 60 ka and is related to volcanism extending beyond the limits of the present caldera.…”

Fluid Vents, Flank Instability, and Seafloor Processes along the Submarine Slopes of the Somma-Vesuvius Volcano, Eastern Tyrrhenian Margin

“…The pattern of volcanic centers has been interpreted as the result of magma ascent along an E-W lithospheric discontinuity separating the central sector from the southern sector of the Tyrrhenian basin (e.g., [10] and references therein). Volcanic activity in the area emplaced throughout a range of eruptive mechanisms, including magmatic, phreatomagmatic, and caldera forming eruptions ( [11], and references therein). Volcanic products of the last ca.…”