Large dyke intrusion and small eruption: The December 24, 2018 Mt. Etna eruption imaged by Sentinel‐1 data

Abstract

On December 24th, Mt. Etna volcano underwent a seismic crisis beneath the summit and upper southern flank of the volcano, accompanied by significant ash emission. Eruptive fissures opened at the base of summit craters, propagating SE‐wards. This lateral eruption lasted until December 27th. Despite the small eruption, seismic swarm and ground deformation were very strong. Sentinel‐1 interferograms show a wide and intense ground deformation with some additional features related to volcano‐tectonic structures. We inverted DInSAR data to characterise the magma intrusion. The resulting model indicates that a large dyke intruded but aborted its upraise at about the sea level; however, this big intrusion stretched the edifice, promoting the opening of the eruptive fissures fed by a shallower small dyke, and activating also several faults. This model highlights that a big intrusion beneath a structurally complex volcano represents a main issue even if the eruption is aborted.

Structural Mapping of Dike-Induced Faulting in Harrat Lunayyir (Saudi Arabia) by Using High Resolution Drone Imagery

“…One of the main questions concerning the 2009 dike intrusion addresses the reason why the dike didn't reach the surface and cause an eruption. Several processes might have prevented further upward dike propagation, e.g., dike depressurization along with compression near its top induced by the graben normal faulting (Xu et al, 2016), reduction in dike overpressure due to magma degassing, a too low regional spreading rate (<1 cm/yr), magma drainage from the preexisting fracture network (see e.g., Bonforte et al, 2019), a stress barrier due to a stiff basaltic layer (Abdelfattah et al, 2017), or other crustal heterogeneities above the propagating dike (Al Shehri and Gudmundsson, 2018).…”

Dyke intrusion and stress-induced collapse of volcano flanks: The example of the 2018 event at Mt. Etna (Sicily, Italy)

“…Etna and transient changes of velocities highlight how the volcano reacts to intense episode of deformation associated with dyke intrusion. Seismic swarm accompanied the intrusion of a N-NW oriented shallow dyke 30 which splays from the summit area down to few kilometres below the sea level, on the top of the high velocity intrusive complex. The shallow portion of the volcano structure, comprising the central high V P plexus, is characterized by broad low V P /V S anomalies, which we interpret as gas-filled volumes.…”

“…During the dyke intrusion, deformation spread over the eastern flank 30 . We observe distinctive time-change of velocity associated with the magmatic intrusion.…”

“…Red stars are M L ≥ 4.0 earthquakes and yellow star is the December 26 M W = 4.9 earthquake. The box indicates the extent of the intrusive dyke [from30 ]. Dashed red lines mark the compressional structure within the sedimentary cover, as retrieved from V P anomalies.…”

Balance Between Deformation and Seismic Energy Release: The Dec 2018 ‘Double-Dike’ Intrusion at Mt. Etna

“…In fact, the more an intrusion extends laterally, the greater the risk that the eruptive fissure and lava flows may approach small towns and villages. Similarly to the 2002 eruption, the intrusive process triggered an acceleration of the eastward sliding of the unstable eastern sector of the volcano (Bonforte et al, 2019). Following the eruptive period, this marked sliding was also accommodated by fault slip that on 26 December culminated with the M L 4.8 earthquake along the Fiandaca fault in the low Eastern flank (Alparone et al, 2020;Giampiccolo et al, 2020).…”