Experimental Characterisation of Slip Properties in Similar and Dissimilar Volcanic and Sedimentary Rocks during Flank Motion at Mount Etna (Italy)
Jackie E Kendrick1, Yan Lavallée
1, Wojciech Rozanski
1, Angela Castagna
2, Michael John Heap
3, Sergio Vinciguerra
4,5, Takehiro Hirose
6 and Donald B Dingwell
7, (1)University of Liverpool, Liverpool, United Kingdom, (2)University of Leicester, Leicester, United Kingdom, (3)Université de Strasbourg, CNRS, Institut Terre et Environnement de Strasbourg, Strasbourg, France, (4)University of Turin, Earth Sciences, Turin, Italy, (5)British Geological Survey Keyworth, Nottinghamshire, United Kingdom, (6)JAMSTEC Japan Agency for Marine-Earth Science and Technology, Kochi Institute for Core Sample Research, Nankoku, Japan, (7)Ludwig Maximilian University of Munich, Earth and Environmental Sciences, Munich, Germany
Contact First Author: Jackie E Kendrick; jackie.kendrick@lmu.de
Previously Published Material: They will be presented in-part at EGU2015
English Abstract:
The edifice of Mount Etna (Italy) is structurally unstable, exhibiting near-continuous ESE sliding along a set of faults that results from interplay between regional tectonics, gravity instability and magma intrusion. Ground deformation and seismic monitoring reveal large-scale flank motion at variable rates. However, the mechanisms controlling this faulting remain poorly constrained. Examination of the fault zones reveals a range of rock types along the different fault segments: fresh and altered basalt, sandstone, clay and limestone. Here, we experimentally investigate the frictional properties of these rocks using rotary shear tests on similar and dissimilar rocks, to better understand episodes of slow flank motion as well as potential rapid and catastrophic sector collapse events.
Experiments were performed at velocities up to 1.2 m/s and at normal stresses up to 1.5 MPa, commensurate with depths of the contacts in the Etna edifice. Friction experiments on solid rocks show a wide range of mechanical behaviour. At high velocity (>0.6 m/s) volcanic rocks tend to melt whereas the clay and limestone do not; rather they decarbonate, which prevents the rock from achieving the temperature required for melting. Experiments on dissimilar rocks clearly show that shear resistance on the slip zone is intermediate between the shear resistances of each component rock individually. Host rock composition affects the composition and viscosity of the resultant frictional melt, which causes fault weakening or strengthening depending on the combination of host rock samples. Friction experiments on clay gouge show the strong rate-weakening dependence of slip in this material as well as the release of carbon dioxide. The range of lithologies encountered by the fault system at Etna serve to complicate the model for flank instability, but these results provide important insights to realistic slip behaviour.
