Using novel, integrated approaches to measure volcanic rock properties
Abstract
What is the scale and extent of heterogeneity in volcanic systems? What influence does this heterogeneity have on permeability, on strength and on elastic properties across scales? And, how can we carefully quantify these parameters, and understand their importance with regard to volcanic deformation and eruptive activity? In volcanic regions, rock properties are often simplified or estimated due to the lack of data, thus making it instructive to provide a more comprehensive catalogue on the different mechanical behaviours of such materials. Here, I will examine how novel, integrated experimental approaches can be utilised to re-calibrate and inform current models in an attempt to tackle this knowledge gap.
Our recent work combining analytical-experimental-kinetic approaches has shed light on material characteristics, and new trends and relationships have been quantified. Volcanic rocks have a complex porosity-permeability relationship dictated by: (1) vesiculation textures (2) compacting, shearing textures; (3) contracting, fractured textures; or (4) any combination of these. Moreover, the sensitivity of these materials (notwithstanding anisotropy) to the effects of confinement differ due to the preferential sealing of fractures, having implications for permeability with depth and for defining failure envelope. Both tensile (UTS) and compressive (UCS) strength, the UTS:UCS ratio and Young's modulus not only co-vary with increasing porosity and permeability, but also with prolonged stressing (i.e., weakening at lower strain-rates), highlighting the importance of considering timescale when quoting material properties. Strength is also sensitive to cyclic deformation and is temperature-dependent owing to several factors; expansion or contraction of constituent phases, healing, breakdown of minerals or phase transitions. To our benefit heterogeneities provide the locus for strain localisation during deformation, creating signals audible on a laboratory (acoustic emissions) and volcanic (seismicity) scale allowing us to probe hidden structures and monitor velocity changes caused by damage accumulation. Our experimental work emphasises the critical role of heterogeneities for understanding process-specific rock properties and modelling hazards.- Publication:
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AGU Fall Meeting Abstracts
- Pub Date:
- December 2018
- Bibcode:
- 2018AGUFM.V23E0124K
- Keywords:
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- 1207 Transient deformation;
- GEODESY AND GRAVITYDE: 1236 Rheology of the lithosphere and mantle;
- GEODESY AND GRAVITYDE: 8445 Experimental volcanism;
- VOLCANOLOGYDE: 8485 Remote sensing of volcanoes;
- VOLCANOLOGY