Yuval Boneh

Graduate Student ('12)

Research Interests

I am interested in the way rocks behave under different conditions and environments and how these affect our understanding of Earth structure and forces. In my studies I use rock deformation experiments to explore the underlining physics of rock deformation. Specifically, I investigated the friction and wear due to sliding along crustal faults and the microstructural evolution due to plastic deformation in the mantle.

Rotary shear apparatus stationed in Oklahoma University (PI – Ze’ev Reches ). In the picture are two blocks of Sierra White granite. UB – upper block and LB – lower block. ED – Eddy sensors. TC – Thermocouples

Wear and friction along faults

Earthquakes occur when the frictional strength of fault decreases, allowing a dynamic unstable slip over the fault plane. I am interested in investigating slip along faults and what enables frictional weakening. My focus was the process of generating fault gouge, i.e. wear-rate, and its evolution in respect to frictional strength. I used ‘wear-maps’ diagram, a tool to characterize wear and friction intensities under different mechanical conditions, to distinguish a transition between brittle to ductile deformation mechanism which correlates with the appearance of shiny slip surfaces.

Boneh, Sagy, Reches, “Frictional strength and wear rate of carbonate faults during high velocity steady state sliding”, EPSL (2013)

Boneh, Chang, Lockner, Reches, “Evolution of wear and friction along experimental faults”, Pure and Applied Geophysics (2014) 

Slip surface observations on Dover limestone samples. (A) low velocity experiments (~ 0.003 m/s), the slip surface is covered with gouge powder. (B) – intermediate velocity experiment (~ 0.05 m/s) the slip surface contain number of shinny patches. (C) high velocity (~0.5 m/s) experiment, the slip surface contain pervasive shiny surfaces

 Seismic anisotropy in the mantle

Griggs apparatus

Thin section of Aheim dunite showing the capsule delineate the sample (black)

Texture evolution for different pre-existing textures modeled using VPSC. Texture evolution is shown through as space of symmetry parameters – Point, Girdle, and Random

Currently, I focus on plastic deformation processes deep in the Earth’s mantle where deformation is accommodated by crystallographic defects. The deformation is detected by probing its anisotropic elastic properties (i.e., seismic anisotropy). I am investigating the effect that deformation history has on the texture evolution of mantle rocks (peridotite). The upper mantle is seismically anisotropic due to its crystals alignment with flow. Seismic waves passing through the upper mantle probe these crystallographic preferred orientation and are usually interpreted as the mantle’s flow direction. I use both experimental and numerical tools in order to assess how an initial condition of pre-existing texture affects the texture evolution. For the experiments I use Griggs rig apparatus with natural sample of Åheim dunite, pressure of 1 GPa and temperature of 1200°C under uniaxial compression. For the numerical models I use ViscoPlastic Self Consistent (VPSC) and D-Rex models to simulate texture evolution from various initial conditions and deformation geometries. My work points out that there is a transient stage of texture alignment where the elastic anisotropy does not represent the mantle kinematics. As such, modeling and interpreting mantle flow, specifically where mantle flow changes its direction, must consider this transient stage in which the seismic anisotropy does not reflect mantle flow.

Boneh and Skemer, The effect of deformation history on the evolution of olivine CPO”, EPSL (2014)

Boneh, Morales, Kaminski, Skemer, “Modeling olivine CPO evolution with complex deformation histories – Implications for the interpretation of seismic anisotropy in the mantle”, G-cubed (2015)