School of Earth and Environment

Katherine Willis Katherine Willis

Postgraduate Researcher

Email address:
Room: 8.153

Affiliation: Institute of Geophysics and Tectonics


I worked in the oil and gas industry before reading for an undergraduate Masters in geology at Cardiff University. I graduated in 2015. Currently I am a PhD student at the University of Leeds working with Prof. Greg Houseman in modelling strain localisation mechanisms in the crust.

I am a member of NERC’s Centre for the Observation and Modelling of Earthquakes and Tectonics, COMET, a collaboration between scientists in Leeds, Oxford, Cambridge, Bristol, UCL, Glasgow, and Reading, and a member of the Institute for Geophysics and Tectonics in the School of Earth and Environment at Leeds.

Outside academia I train in Japanese martial arts, (jiu jitsu, aikido and recently started in kenjutsu) and spend my weekends hill-walking. I am a field volunteer at Whixal Moss, the UK's third largest lowland peatbog, which is managed by Natural England.

My linked in profile can be viewed at:


MESci, Geology. Cardiff University.

HND Marine Engineering. South Tyneside College.


Geological Society

Research Interests

I am interested in the mechanisms of fault development and propagation, and sea-floor spreading.

Teaching Interests

I demonstrate for the following module.

SOEE2050: Deformation Porcesses

Project details

Project title

Mechanisms of strain localization in the crust.


Professor Greg Houseman, Professor Tim Wright, and Professor Andy Hooper

Start date

1 October 2015

Project outline

Deformation of the continents involves multiple processes whose effects are summarised by constitutive relations that describe how strain rate varies with stress. For most of these mechanisms we can talk about an effective viscosity, proportional to the local ratio of deviatoric stress to strain rate. The simplest idealisation of continuum deformation is the constant viscosity fluid, a model that has been important in various geological contexts from post-glacial uplift to channel flow in the lower crust. The viscous flow model arises directly from microscopic models for the diffusion of atomic species and dislocations, and thus the coefficient of viscosity may vary with temperature, pressure, grain size, and stress. Deformation, however, induces various feedback mechanisms which often can cause a local decrease in the viscosity coefficient. The work done in deformation can cause a reduction in grain size, an increase in dislocation density, and an increase in temperature. All of these feedback mechanisms can in principle lead to a localisation of deformation, typically manifested by the formation of viscous shear zones and faults.

Large displacement surface faults probably are closely related to ductile shear zones in the lower crust (Vauchez et al., 2012). The various feedback mechanisms identified above can promote localization and induce formation of a ductile shear zone initially established in response to heterogeneous variation in the strength parameter (e.g. Dayem et al., 2010) or presence of faults (e.g. Barr and Houseman, 1996). While earth materials are essentially visco-elastic on the time-frame of the earthquake cycle, the logically simplest formulation of visco-elasticity which permits the most general type of ductile deformation law is the Maxwell assumption that elastic and viscous strains are simply additive. Recent analyses of post-seismic relaxation show that the creep deformations evident on the post-seismic timescale are indeed compatible with estimated creep parameters for long-term deformation (Yamasaki and Houseman, 2012).

This project will obtain numerical solutions to viscous deformation problems incorporating these feedback systems in order to develop understanding of when and how shear zones are likely to develop in the lower crust and upper mantle. Where the principal deformation mechanism is crystalline plasticity, the development of a crystalline preferred orientation (CPO) is both an important consequence of the deformation and an important aspect of the feedback mechanism. Numerical solutions to this problem therefore require a mechanism for keeping track of the magnitude and orientation of the CPO, together with an anisotropic formulation of the viscous constitutive law. I am undertaking systematic numerical experimentation aimed at understanding the role and significance of the various feedback mechanisms that cause strain localization.