INGV reported that the mean amplitude of volcanic tremor at Etna had been increasing.
Notably, the increase since mid-August had reached significant values by 6 September and were comparable to those values recorded just before the December 2018 eruption, and higher than those observed before the eruptive episodes during May-July 2019.
Inclement weather prevented visual observations of the summit craters, though mountain guides reported characteristic sounds of Strombolian activity at the Bocca Nuova crater on 6 September.
A sudden increase in volcanic tremor amplitude was recorded at 0449 on 9 September, and by 0536 Strombolian activity at Northeast Crater (NEC) was visible.
At 1050 volcanic tremor amplitude again increased, with signals localized beneath NEC.
Diffuse ash plumes rose from the crater and dissipated near the summit.
Source: Sezione di Catania - Osservatorio Etneo (INGV)