A small-scale stalled intrusive episode (micro-dyke) at Mt. Etna: the November 15, 2022 case

Abstract At active volcanoes, magmatic intrusions may not always reach the surface and may instead stall inside the edifice. Here, we investigate a stalled intrusion at Mt. Etna, Italy, using geophysical data (tilt, seismicity and volcanic tremor). On November 15, 2022, tilt changes and a shallow seismic swarm accompanied a small-scale intrusive episode that did not lead to the opening of eruptive fissures. The intrusion caused ground deformation that was only detected by the permanent clinometric network. The tilt data were consistent with the intrusion of a dyke of dimensions 600 × 150 (m) located in the summit area at a depth of 2.0 (km) below the surface. Through a Coulomb stress analysis, we determined that this intrusion activated the highly fractured South Rift zone, giving rise to a seismic swarm and causing volcanic tremor fluctuations. We found a notable temporal correlation between the main phases of the ongoing intrusion and the occurrence of the seismicity. The volcanic tremor fluctuations synchronized with the opening and stopping phases of the intrusion, recording the highest peaks in amplitude when the dyke propagation slowed down. Therefore, we determined that the November 2022 magmatic process was an aborted intrusion limited by magma supply, which occurred at the contact between the volcanic pile and the sedimentary basement. Similar events, detected exclusively by high-precision instruments, namely tiltmeters and strainmeters, are rare at Mt. Etna, and their detection is important to improve the forecasting of eruptions.