Sliding episodes during the 2002–2003 Stromboli lava effusion: Insights from seismic, volcanic, and statistical data analysis

Abstract

[1] Repeated phenomena of flank instability accompanied the 28 December 2002 to 21 July 2003 eruption of Stromboli volcano. The major episodes were two tsunamigenic landslides on 30 December 2002, 2 d after the volcano unrest. After 30 December, sliding processes remodeled the area affected by slope instability. We propose analyses of 565 sliding episodes taking place from December 2002 to February 2003. We try to shed light on their main seismic features and links with the ongoing seismic and volcanic activity using variogram analysis as well. A characterization of the seismic signals in the time and frequency domains is presented for 185 sliding episodes. Their frequency content is between 1 Hz and 7 Hz. On the basis of the dominant peaks and shape of the spectrum, we identify three subclasses of signals, one of which has significant energy below 2 Hz. Low-frequency signatures were also found in the seismic records of the landslides of 30 December, which affected the aerial and submarine northwestern flank of the volcano. Accordingly, we surmise that spectral analysis might provide evidence of sliding phenomena with submarine runouts. We find no evidence of sliding processes induced by earthquakes. Additionally, a negative statistical correlation between sliding episodes and explosion quakes is highlighted by variogram analysis. Variograms indicate a persistent behavior, memory, of the flank instability from 5 to 10 d. We interpret the climax in the occurrence rate of the sliding processes between 24 and 29 January 2003 as the result of favorable conditions to slope instability due to the emplacement of NW-SE aligned, dike-fed vents located near the scarp of the landslide area. Afterward, the stabilizing effect of the lava flows over the northwestern flank of the volcano limited erosive phenomena to the unstable, loose slope not covered by lava.

Shifts in the eruptive styles at Stromboli in 2010–2014 revealed by ground-based InSAR data

“…Ground deformation at Stromboli, Italy, due to conduit processes may be difficult to detect and possibly related to strong explosions 8 9 10 or syn-effusive deflations 11 . Both the 2002–2003 and 2007 flank eruptions completely drained the shallow storage system, as testified by the funnel-like vertical failure of the summit crater terrace associated with this eruption 11 12 13 14 15 16 17 18 and to the lowering of the VLP source location 19 . The complete absence of strombolian activity is considered further evidence of the drainage of the shallower part of the Stromboli storage system 19 .…”

Multi-parametric study of an eruptive phase comprising unrest, major explosions, crater failure, pyroclastic density currents and lava flows: Stromboli volcano, 1 December 2020–30 June 2021

“…These collapses can be triggered by: 1) dike intrusion and magma fingering in between the loose breccia comprising the cinder cone (Acocella and Tibaldi, 2005;Calvari et al, 2016); 2) magmastatic pressure increase when the magma level within the conduit increases (Di Traglia et al, 2018); or 3) by powerful major explosions such as the 16 November 2020 event (Calvari et al, 2021). In addition, the opening of eruptive fissures and/or vents along the SdF slope can result in instabilities of portions of the slope (Calvari et al, 2005(Calvari et al, , 2010, increasing the number of landslides (Martini et al, 2007;Falsaperla et al, 2006Falsaperla et al, , 2008. The drainage of the shallow conduit may produce summit collapses and graben (Neri and Lanzafame, 2009) changing the capacity of the shallow feeder conduit and resulting in a greater number of major explosions and increased output rate (Coppola et al, 2012;Calvari et al, 2014;Civico et al, 2021).…”

First muography of Stromboli volcano

“…The frequency of occurrence of “major explosions” and effusive phases due to overflows from the summit craters increased. The changes of the eruptive activity occurred at Stromboli from April 2007 to December 2012 is interpreted as the effect of “a wider and hotter uppermost conduit, initiated by movements that occurred in the Sciara del Fuoco after the 2002 landslide events 50,51 that followed the graben-like collapses that occurred during the 2007 eruption, which involved the entire summit crater zone” 52 .…”