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Pennacchia, Francesco
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Pennacchia, Francesco
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- PublicationOpen AccessThe Effect of Conduit Walls Roughness on Volcanic Jets and Their Seismo‐Acoustic Radiation: An Experimental Investigation(2023-10-02)
; ; ; ; ; ; ; ; ; ; ; ; ; ;; To explore the effect of conduit roughness on volcanic jet dynamics and on the related seismo-acoustic radiation we performed a series of shock-tube experiments using pipes with variable inner surface fractal dimension D. Variable starting pressure produced subsonic to supersonic jets visualized using high-speed shadowgraph and recorded with an array of accelerometers and microphones. At all starting pressures, increasing D increases the energy transfer from the gas to the conduit walls, decreasing the jet exit velocity (Mach number) and, for supersonic cases, the related shock-cell spacing, and increasing the seismic to acoustic radiation amplitude ratio. The roughness-induced changes in jet velocity and turbulence affect the dominant sources of the jet noise and modulates the spectral properties of the acoustic signals. From our study we show that conduit wall roughness is an important and yet largely neglected factor in the dynamics of explosive volcanic eruptions and their monitored geophysical signals.87 10 - PublicationOpen AccessUncovering the eruptive patterns of the 2019 double paroxysm eruption crisis of Stromboli volcano(2021-07-09)
; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; In 2019, Stromboli volcano experienced one of the most violent eruptive crises in the last hundred years. Two paroxysmal explosions interrupted the 'normal' mild explosive activity during the tourist season. Here we integrate visual and field observations, textural and chemical data of eruptive products, and numerical simulations to analyze the eruptive patterns leading to the paroxysmal explosions. Heralded by 24 days of intensified normal activity and 45 min of lava outpouring, on 3 July a paroxysm ejected ~6 × 107 kg of bombs, lapilli and ash up to 6 km high, damaging the monitoring network and falling towards SW on the inhabited areas. Intensified activity continued until the less energetic, 28 August paroxysm, which dispersed tephra mainly towards NE. We argue that all paroxysms at Stromboli share a common pre-eruptive weeks-to months-long unrest phase, marking the perturbation of the magmatic system. Our analysis points to an urgent implementation of volcanic monitoring at Stromboli to detect such long-term precursors.1177 34