High resolution monitoring of active faulting at the instable flank of Mt. Etna

Etna-Creep monitors fault displacement at localized site along active faults on the instable SE flank of Mt. Etna. Currently two instruments are installed across the Macchia Fault in the S. Leonardello - Macchia Graben System close to the coastline. Creepmeters can capture fault creep, slow slip events as well as triggered slip events from near field or far field sources, and allow us to detect signals of volcano-tectonic interactions. Our instruments monitor continuous slip with a resolution of 1 micrometer and a sampling rate of 2/min. These installations complement the GEOSEA array (https://www.geomar.de/en/news/article/geosea-array-records-sliding-of-mount-etnas-southeastern-flank) offshore Catania and strongly link research on flank instability processes onshore with the offshore GEOMAR activities. Installed in 2022, these instruments already recorded several triggered slip events, characterised also by sudden acceleration episodes of slip. This dataset enables us to study how extensional faulting at the SE flank of Mt. Etna contributes to the slow sliding of the flank into the Ionian Sea. With the high temporal resolution of this network, we also retrieve information about potential triggering sources reflected in the stress regime change allowing the unclamping of the monitored fault. Dynamic triggering caused a slip event on the Macchia fault during the passage of surface waves during the February 6th 2023, M7.8 Kahramanmaras earthquake in Turkey. Additional slip events were triggered after an earthquake offshore Catania (M4.5) and by other earthquakes in the Mediterranean. Shallow micro-seismicity along the Acicatena fault, located close to the monitored fault, is synchronous with events at the monitored Macchia fault showing elastic unclamping with no permanent slip. These events demonstrate the susceptibility of the extensional fault system to external perturbation (i.e. triggering). With Etna-Creep we hope to be able to better understand the contribution of these faults to the SE-ward motion of the Etna’s eastern flank as well as its driving processes, but also insights into the basic process of tectonic loading on earthquake faults.