Fracture density analysis at Stromboli Volcano, Italy: implications to flank stability

T Alcock,F Vagnon,P Benson,S Vinciguerra

doi:10.1088/1755-1315/833/1/012086

Abstract

Stromboli volcano has experienced four sector collapses over the past 13,000 years, resulting in the formation of the Sciara del Fuoco (SDF); a horseshoe-shaped flank collapse scarp where episodes of instability are continuously observed and recorded. A NE / SW striking rift zone across the SDF and the western sector of the island is inferred to be a potential weakness zone for further instability episodes. This study reports new data of fracture density using remote sensing imagery, across within and outside the rift zone, to identify areas of damage that could reduce the edifice strength and promote fracturing. Pleiades satellite data of 0.5 m resolution was processed to highlight 23635 distinct linear features, determine fracture density across the island, and identify key areas of macro-scale weakness on the volcano. These data suggest that the SW sector of the island, including the summit area and the slopes of SDF, have an average fracture density between 1.18 – 2.73 × 10−5m−2 in contrast to the rest of the volcano that has an average fracture density of 4.56 × 10−6m−2. Analysis was also conducted on the orientation of fracture strikes across the volcanic edifice by analysing fracture data specifically associated with areas of intrusions and fissures: the NW / SE rift zone and the SDF. Preliminary results show that the average fracture strike ranged from between 030 – 047 NE/SW and thus broadly parallel to the inferred rift axis.

Highlights

Stromboli is the north easternmost island of the Aeolian archipelago in the Tyrrhenian Sea
A fracture density analysis has been performed on the island of Stromboli using remote sensing (Pleiades 0.5m resolution satellite data) to assess the nature and localisation of fracturing processes related to regional tectonics and the continuous eruptive activity
Fracture density assessment around the Sciara del Fuoco (SDF) is a useful method to determine the main points of weakness where sheet intrusions, previously mapped by Tibaldi et al, [4], have influenced the stability of the slope subsequently leading to flank collapse events

Summary

Introduction

Stromboli is the north easternmost island of the Aeolian archipelago in the Tyrrhenian Sea. Over the last 13 ka the island has experienced multiple phases of eruptive activity and subsequent sector collapses This has resulted in the formation of multiple steep depressions (flank collapse scarps) around the island such as the well-known Sciara del Fuoco (SDF) on the NW side of the volcano. Field investigation carried out by Tibaldi et al.,[4] presents 109 sheet intrusions mapped around the Stromboli edifice, striking mostly NE and becoming more abundant toward the rift axis. They concluded that the presence of the rift zone controlled the NE/SW emplacement of sheets across the volcano. Using high resolution satellite data, this investigation aims to systematically investigate this hypothesis by quantifying the extent to which the rift zone and areas of intrusive events have influenced the location, direction and density of fractures across the volcano

Methods

Results

Conclusion