University College Dublin
PhD Real-time determination of the properties of deep (remote) in situ earth fractures
Chris Bean, School of Geological Sciences, University College Dublin, Ireland
Sergei Lebedev, Dublin Institute for Advanced Studies, Dublin, Ireland
John McCloskey, School of Environmental Sciences, University of Ulster, Coleraine, N. Ireland
Project code MOD1
Fractures play critical roles in a wide range of earth science problems and have been very widely studied. However most studies of fracture properties are confined to observing fractures that are currently exposed on or are very close to the earth's surface while many earth processes that are of interest take place several hundred metres to kilometres beneath the surface. Forensic seismic measurements open a window to the determination of these in situ rock fracture properties, deep below the surface. As seismic waves pass through fractures they are modified in amplitude, frequency and propagation speed, leaving 'characteristic signatures' on the waves which pass through the fractures. Furthermore, temporal changes in these fracture properties can be used to determine important related parameters, such as the temporal evolution of stress and fluid flow in the earth (e.g. beneath volcanoes even prior to visible inflation, in CO2 sequestration reservoirs, in unstable land masses prior to land-slides etc.). A key determinable fracture parameter is its stiffness which can acts as a proxy for how fluids flow through the fracture and for fracture strength. However a key challenge is to better understand how fracture stiffness scales in space and to develop a methodology for remotely detecting fracture population stiffness and its temporal evolution, from seismic data. In this work we will address this problem by making field seismic measurements of wave propagation across fractures of different scale sizes from the sub-metre scale through to the 100s km scale. Field scale measurements will be undertaken in disused quarries, intermediate scale measurements in underground tunnels on Teide volcano Tenerife and the 100s km scale measurements using a new broadband seismic array ('Ireland array'), in collaboration with the Dublin Institute for Advanced Studies (DIAS). Field observations will be complemented by high-end computational simulations of seismic waves in fracture populations and fracture-fracture stress transfer interaction modelling in collaboration with the University of Ulster, at Coleraine. The impact will be an improved understanding of deep (remote) in situ fracture properties (and their time evolution) for a wide range of earth system applications.
To apply, please see http://www.ucd.ie/earth/graduatetraining/phdprogrammeinearthandnaturalsciences/applyingforaphdposition/
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