[Eoas-seminar] Geophysics Job Talk Today @ 3:30 PM

eoas-seminar at lists.fsu.edu eoas-seminar at lists.fsu.edu
Tue Feb 16 10:04:53 EST 2021


Title: The steady-state and transient strength of rocks: Recent advances and future directions


The brittle and viscous rheology (flow) of Earth’s lithosphere (the outer ~100 km of rock) exerts a first order control on numerous geological phenomena such as the nucleation of earthquakes, post-seismic creep, post-glacial isostatic readjustment, and large-scale bending of tectonic plates at subduction zones. Because these processes occur over timescales of decades to millions of years, it is not straightforward to infer the strength of deforming rocks solely from geophysical observations. Numerical modeling is another commonly used and complementary approach, but quantitative constitutive laws are required as inputs. Thus, experimental rock mechanics has become a critical link to understanding geophysical and geodynamical phenomena by developing steady-state “flow laws” to describe the strength of rocks as a function of variables such as temperature, pressure, deformation rate, and grain size. However, many open questions remain on the details of the micromechanics of deformation at steady-state, and no physics-based transient “flow laws” exist to describe the emerging richness and variability of deformation around major fault zones (e.g., slow slip earthquakes and time-dependent viscosity).

In this talk, I will present some of my major contributions to rock deformation over the past few years, which utilize non-conventional experimental rock deformation techniques such as nanoindentation and uniaxial stress-reduction tests. These unique methods allow me to achieve deformation conditions that are unattainable in more conventional apparatus. My work thus far has culminated in a new microphysics-based model that can capture both the steady-state and transient deformation of rocks at high temperature in the laboratory. The microphysical mechanisms that give rise to the complex behavior also occur at deformation conditions over the entire thickness of Earth’s lithosphere, suggesting that many different geophysical and geodynamical processes may be controlled by the same microphysics. This view of rock deformation is significantly more unifying than current paradigm, explains many recent observations of deformation in Earth, provides the first physics-based constitutive law for transient deformation in a geologic material, and lays out several predictions and hypotheses that can be tested in the laboratory or compared to naturally deforming rocks.
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