Ground deformation reveals the scale-invariant conduit dynamics driving explosive basaltic eruptions.

The mild activity of basaltic volcanoes is punctuated by violent explosive eruptions that occur without obvious precursors. Modelling the source processes of these sudden blasts is challenging. Here, we use two decades of ground deformation (tilt) records from Stromboli volcano to shed light, with unprecedented detail, on the short-term (minute-scale) conduit processes that drive such violent volcanic eruptions. We find that explosive eruptions, with source parameters spanning seven orders of magnitude, all share a common pre-blast ground inflation trend. We explain this exponential inflation using a model in which pressure build-up is caused by the rapid expansion of volatile-rich magma rising from depth into a shallow (<400 m) resident magma conduit. We show that the duration and amplitude of this inflation trend scales with the eruption magnitude, indicating that the explosive dynamics obey the same (scale-invariant) conduit process. This scale-invariance of pre-explosion ground deformation may usher in a new era of short-term eruption forecasting.

The LVD signals during the early-mid stages of the L'Aquila seismic sequence and the radon signature of some aftershocks of moderate magnitude.

The L'Aquila seismic swarm culminated with the mainshock of April 6, 2009 (ML = 5.9). Here, we report and analyze the Large Volume Detector (LVD, used in neutrinos research) low energy traces (∼0.8 MeV), collected during the early-mid stages of the seismic sequence, together with the data of a radon monitoring experiment. The peaks of LVD traces do not correlate with the evolution and magnitude of earthquakes, including major aftershocks. Conversely, our radon measurements obtained by utilizing three automatic stations deployed along the regional NW-SE faulting system, seem to be, in one case, more efficient. In fact, the timeseries collected on the NW-SE Paganica fracture recorded marked variations and peaks that occurred during and prior moderate aftershocks (with ML > 3). The Paganica monitoring station (PGN) seems to better responds to active seismicity due to the fact that the radon detector was placed directly within the bedrock of an active fault. It is suggested that future networks for radon monitoring of active seismicity should preferentially implement this setting.

Developments in real-time radon monitoring at Stromboli volcano.

We present the results of one year of continuous radon monitoring at Stromboli volcano collected at two automated real-time stations. These were deployed on the NE flank (at 520 m a.s.l.) and within the summit area (900 m a.s.l.). Higher daily emissions at the lower station approached 4,200 Bq/m³, with bulk averages around 1,800 (±980) Bq/m³; whereas the summit station reached peak values of 23,000 Bq/m³ and bulk averages of 12,500 Bq/m³ (±4,000). Negative correlations are observed between radon emissions, soil temperature and, to a lesser extent, atmospheric pressure. In contrast, increases in radon concentrations were observed during periods of higher rainfall conditions. Therefore, trends in radon concentrations may be decoupled from those of other geochemical parameters (CO2 fluxes and CO2/SO2 plume ratios) during periods of heavy to moderate rainfalls. Multiple Linear Regression statistics (including the effects of soil temperature, atmospheric pressure and tidal forces) led us to compute the residuals given by the difference of measured and calculated ²²²Rn concentrations. The cross-check between the daily measured radon activities and the absolute variations in radon residuals, for the data collected at the summit station, give us the opportunity to suggest a methodological approach that can be used in the attempt of predicting some major changes in volcanic activity.