Slope instability induced by volcano-tectonics as an additional source of hazard in active volcanic areas: the case of Ischia island (Italy)

Abstract

Ischia is an active volcanic island in the Gulf of Naples whose history has been dominated by a caldera-forming eruption (ca. 55 ka) and resurgence phenomena that have affected the caldera floor and generated a net uplift of about 900 m since 33 ka. The results of new geomorphological, stratigraphical and textural investigations of the products of gravitational movements triggered by volcano-tectonic events have been combined with the information arising from a reinterpretation of historical chronicles on natural phenomena such as earthquakes, ground deformation, gravitational movements and volcanic eruptions. The combined interpretation of all these data shows that gravitational movements, coeval to volcanic activity and uplift events related to the long-lasting resurgence, have affected the highly fractured marginal portions of the most uplifted Mt. Epomeo blocks. Such movements, mostly occurring since 3 ka, include debris avalanches; large debris flows (lahars); smaller mass movements (rock falls, slumps, debris and rock slides, and small debris flows); and deep-seated gravitational slope deformation. The occurrence of submarine deposits linked with subaerial deposits of the most voluminous mass movements clearly shows that the debris avalanches impacted on the sea. The obtained results corroborate the hypothesis that the behaviour of the Ischia volcano is based on an intimate interplay among magmatism, resurgence dynamics, fault generation, seismicity, slope oversteepening and instability, and eruptions. They also highlight that volcano-tectonically triggered mass movements are a potentially hazardous phenomena that have to be taken into account in any attempt to assess volcanic and related hazards at Ischia. Furthermore, the largest mass movements could also flow into the sea, generating tsunami waves that could impact on the island's coast as well as on the neighbouring and densely inhabited coast of the Neapolitan area

Development and recent activity of the San Andrés landslide on El Hierro, Canary Islands, Spain

“…Terzaghi, 1950;Moon and Simpson, 2002;Baldi et al, 2008) and also show that repeating activity of DSGSDs or their parts is common in a variety of environments (Moro et al, 2007;Vilímek et al, 2007;Klimeš et al, 2009a;Klimeš et al, 2009b;Pánek et al, 2011;Crosta et al, 2004;2014). This also includes volcanic islands where continuous creep or repeating sliding activity of similar landslides has been described in other works (Pararas-Carayannis, 2002;Seta et al, 2011;Hunt et al, 2011). All of the above-mentioned findings suggest continuing development of the SAL in the future.…”

“…Nevertheless, some preceding works on volcanic islands have also highlighted the importance of structural conditions for landslide development. Carracedo et al (2009) stressed the importance of a wedge failure mechanism for their initiation, while Rodríguez-Losada et al (2009) mentioned the importance of structural weakened zones for large flank collapse and the location of debris avalanche source areas (Seta et al, 2011).…”

The Relationship between InSAR Coseismic Deformation and Earthquake-Induced Landslides Associated with the 2017 Mw 3.9 Ischia (Italy) Earthquake

“…The steep angles and the poor geotechnical properties of the outcropping lithologies have favored slope instabilities, resulting in shallow mass movements and large rock and debris avalanches. Indeed, slope instability-related deposits, mainly triggered by local seismic activity, are identified in and around the island [4,25,[27][28][29]. In particular, volcaniclastic deposits with variable thickness and strength cover the north-western flanks of Mt.…”

Fire resistance of the Mt. Epomeo Green Tuff, a widely-used building stone on Ischia Island (Italy)

“…Epomeo and Mt. Nuovo as a result of historic rock avalanches [Seta et al 2012;Della Seta et al 2015] ( Figure 1C-D).…”