In active volcanic systems, the elevated pressurization of fluids and the movement of melt materials have an enormous influence on the stress-state of rocks and their mechanical behavior. We use seismic ambient noise to evaluate the static seismic velocity variations related to long-term volcanic deformation, and the dynamic changes associated with the 2017 Casamicciola earthquake (Mw 3.9), in the active volcanic complex of the Ischia Island (Italy). Our study reveals a significant dynamic velocity reduction mostly related to the near-surface damage, with a permanent drop near the red zone, that we posit to be related to the documented landslides and the subsidence observed immediately after the earthquake. We also report a positive long-term linear trend of velocity variations, sensitive to a generalized contraction of the Ischia Caldera that we revealed with geodetic modeling. Our results suggest a depressurization of the shallow hydrothermal system, through degassing along faults or sills.

The use of seismic catalogs enhanced through advanced detection techniques improves the understanding of earthquake processes by illuminating the geometry and mechanics of fault systems. In this study, we performed accurate hypocentral locations, source parameters estimation and stress release modelling from deep catalogs of microseismic sequences nucleating in the complex normal fault system of the Southern Apennines (Italy). The application of advanced location techniques resulted in the relocation of ~ 30% of the earthquakes in the enhanced catalogs, with relocated hypocenters clearly identifying local patches on kilometer-scale structures that feature consistent orientation with the main faults of the area. When mapping the stress change on the fault plane, the inter-event distance compared to the size of the events suggests that the dominant triggering mechanism within the sequences is static stress transfer. The distribution of events is not isotropic but dominantly aligned along the dip direction. These slip-dominated lineations could be associated with striations related to fault roughness and could map the boundary between locked and creeping domains in Apulian platform and basement.

We use a newly updated GPS dataset and the GPS Imaging technique to show that the relief of the Apennines Mountain chain in Italy is currently increasing along its entire length by 1-2 mm/yr. We image positive uplift along the entire length of the Apennine crest including the northern Apennines, Calabria and northern Sicily. The maximum uplift rate is aligned with the topographic drainage divide, the greatest elevations and the zone of horizontal extension accommodating east-northeast translation of the Adriatic microplate relative to the Tyrrhenian Basin. Uplift occurs in a 100 - 150 km wide zone with a profile similar to the long wavelength topography, but not to shorter wavelength topography generated by active faulting and erosion. A zone of lower amplitude uplift aligns with the restive volcanic fields and high geothermal potential west of the Apennines, e.g., at Campi Flegrei, Alban Hills, and Monte Amiata-Larderello. Several factors including consistency of the geodetic rate with geologic uplift rates, and incompatibility with transient hydrological or earthquake cycle effects imply that it is a long-lived feature. Uplift occurs despite that the expected consequence of extension is crustal thinning and subsidence, suggesting a causal relationship between gravitational forces and active extension. Anomalies in gravity and upper mantle seismic velocity suggest that elevation gain is driven by forces originating in the mantle. We use these observations to address the hypothesis that these forces result from upward flow of asthenosphere beneath the Apennines, although the spatial and temporal scale of the mantle circulation is unclear.