Massive emissions of deep CO ₂ coupled to the 2009–2018 Central Italy earthquakes.

Summary. Scattered waves observed at the seismographs of the National Italy's seismic network have been used to investigate the intrinsic dissipation and scatt

Intrusions are a ubiquitous component of mountain chains and testify to the emplacement of magma at depth. Understanding the emplacement and growth mechanisms of intrusions, such as diapiric or dike-like ascent, is critical to constrain the evolution and structure of the crust. Petrological and geological data allow us to reconstruct magma pathways and long-term magma differentiation and assembly processes. However, our ability to detect and reconstruct the short-term dynamics related to active intrusive episodes in mountain chains is embryonic, lacking recognized geophysical signals. We analyze an anomalously deep seismic sequence (maximum magnitude 5) characterized by low-frequency bursts of earthquakes that occurred in 2013 in the Apennine chain in Italy. We provide seismic evidences of fluid involvement in the earthquake nucleation process and identify a thermal anomaly in aquifers where CO₂ of magmatic origin dissolves. We show that the intrusion of dike-like bodies in mountain chains may trigger earthquakes with magnitudes that may be relevant to seismic hazard assessment. These findings provide a new perspective on the emplacement mechanisms of intrusive bodies and the interpretation of the seismicity in mountain chains.

Summary. We investigated the intrinsic dissipation and scattering properties of the lithosphere under the Friuli region (northeastern Italy) using two hypothes

We find that the double‐difference relocated seismicity, which occurred over the last 30 years at Campi Flegrei, was triggered by the uprising of fluids preferentially concentrated along onshore and offshore NW striking preexisting caldera faults. Focal volumes of the 2005–2014 seismicity do not overlap that of the 1982–1984 period, when a major uplift of 1.8 m occurred in the central sector of the caldera. This indicates a transition from an elastic to a plastic behavior due to fluid saturation and heating of the rocks in the hydrothermal reservoir. The 2012–2014 deeper earthquakes are located in a low V_P/V_S zone at the western boundary of the hydrothermal reservoir, where a volume increase from a magmatic body at 3.5 km depth has been recognized. The progressive rheological change from elastic to plastic in the upper 4 km of the crust implies that a slow upward migration of magma may not necessarily be preceded by earthquakes or swarms.