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Strain and fault evolution during gravitational volcano collapse: experiments with different substrata geometries

Julia Knüppel1,  Sylvain Mayolle1, Matthias Rosenau2, and Morelia Urlaub1

  • Affiliations: 1GEOMAR Helmholtz Centre for Ocean Research Kiel, 24148 Kiel, Germany; 2 Helmholtz Centre Potsdam, German Research Centre for Geosciences, GFZ, 14473 Potsdam, Germany.

  • Presentation type: Poster

  • Presentation time: Tuesday 16:30 - 18:30, Room Poster Hall

  • Poster Board Number: 62

  • Programme No: 6.3.21

  • Theme 6 > Session 3

Abstract

Many volcanoes on Earth show evidence of gravitational collapse of their entire structure or a sector, at rates ranging from slow spreading and sagging of a few millimetres to centimetres per year to catastrophic collapse. While deformation at the surface of volcanoes can be observed using geodetic methods, its relation to structures inside the volcanic edifice and below, i.e. basement geometries is not systematically explored. This study uses analogue models composed of a ductile layer (the detachment) overlaid by a brittle layer (the basement) with different slope geometries and a cohesive conical edifice (the volcano) to experimentally investigate how the geometry of a volcano's basement controls surface deformation under gravitational loading. Therefore, we vary systematically the angle of an implemented basement slope, and the distance between a fixed slope and the volcano. We observe generally lower deformation rates with decreasing basement slope angle and increasing distance between volcano and slope. Transtensional faults develop mainly on the part of the edifice facing the basement slope. Grabens narrow from the peak toward the edifice base. The faults are activated in a stick-slip manner, with a decrease in activity frequency with time. From the strain field analysis, we see compressional structures at the summit, which are more likely activated after extensional deformation in the lower part of the edifice. Based on these new models, we discuss how the fault pattern on the analogue volcanic edifice and fault activation with time are perturbed by the basement parameters, i.e. slope inclination or distance to slope.