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Insights from direct shear experiments into the stability of thrust sheets buttressing the submarine flank of Kilauea volcano (Hawaii, USA)

Fiene Stoepke 1, Matt J. Ikari2, Julia K. Morgan3, Morelia Urlaub1,4

  • Affiliations:  1GEOMAR Helmholtz-Zentrum für Ozeanforschung Kiel, Kiel, Germany; 2Marum -- Zentrum für Marine Umweltwissenschaften der Universität Bremen, Bremen, Germany; 3Rice University, Department of Earth, Environmental and Planetary Sciences, Houston, United States; 4Institut für Geowissenschaften, Christian-Albrechts- Universität zu Kiel, Kiel, Germany 

  • Presentation type: Poster

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

  • Poster Board Number: 157

  • Programme No: 2.2.21

  • Theme 2 > Session 2

Abstract

The south flank of Kilauea volcano (Hawaii, USA) is mobile and is sliding seaward along a basal décollement at rates of at least ~10 cm/yr. The slip is accompanied by earthquakes and landslides. The Hilina Slump rides on top of the mobile flank but it has not yet failed catastrophically as is observed elsewhere on the islands. It is suggested that stacked thrust sheets at the toe of the submarine flank buttress and thereby stabilize the active slump. The mechanical properties of the slump and thrust sheets are poorly known, but could play a role in their deformation behaviors and stability of Kilauea's mobile flank. We performed direct shear experiments on samples collected from submarine exposures of the thrust sheets and the Hilina Slump to better understand the mechanical behavior of these two systems. Our results show that both velocity-weakening and velocity-strengthening frictional behavior are observed for the tested samples. The observed friction velocity dependence depends on the sliding velocity, with velocity-strengthening behavior occurring predominantly at low velocities. Intact samples are stronger and show more velocity-strengthening behavior, compared to powdered rocks which are weaker and show more velocity-weakening behavior. The powdered material is representative of pre-existing fault zones and thus, we can expect potentially unstable sliding behavior for the thrust sheets. Moreover, stick-slip behavior is observed for altered surface sediments of the Hilina Slump. Thus, material behavior across the submarine flank is very variable which might explain the occurrence of different types of deformation structures and slip behaviors at Kilauea.