Long period quakes linked to Mefite D'Ansanto (Italy) mantellic CO2 emissions.

Mefite D’Ansanto is a remarkable mantle origin CO2 emissions system, and the understanding of the relative source mechanisms is one of the fundamental aspects for the comprehension of the evolution of the southern Apennines active dynamics. Moreover, due to its lively activity in a nearly quiet place, Mefite also represents a natural laboratory for the investigation of hydrothermal system dynamics. The seismic wavefield sourced by these CO2 emissions is complex, characterized by a background stationary hydrothermal tremor, with intermittent superposition wavetrains of variable duration. Here we focus on the transient signals generated by the emissions, which show a spectral content in 0.7–7.0 Hz and a peculiar waveform, described here for the first time. Due to their similarities with Long Period earthquakes occurring in volcanic/hydrothermal systems, we classify them as LP quakes and investigate their propagation and source processes. The Mefite LPs appear to be a mixture of P- and surface waves, generated at a depth slightly greater than that of the hydrothermal tremor and likely associated with bubbling mechanisms.