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SUMMARY:When rocks push back:  Angry dislocations and their influence on 
 seismology and geodynamics - Lars Hansen (University of Minnesota) 
DTSTART:20251022T150000Z
DTEND:20251022T160000Z
UID:TALK239374@talks.cam.ac.uk
CONTACT:Adriano Gualandi
DESCRIPTION:The rheological properties of rocks and minerals control a wid
 e variety of large-scale processes in Earth's interior. These processes in
 clude—in order of decreasing timescales—mantle convection and the stre
 ngth of the lithosphere\, glacial isostatic uplift and its influence on se
 a-level rise\, postseismic creep and reloading of faults after earthquakes
 \, the attenuation of teleseismic waves\, and the frictional stability of 
 fault gouge that controls earthquake nucleation. Fundamentally\, those rhe
 ological properties are controlled by underlying microphysical processes w
 ithin the constituent minerals. The primary microphysical process is the 
 movement and interaction of crystal dislocations. We have identified that 
 the elastic interactions of dislocations lead to a directional internal s
 tress\, often referred to as a backstress\, and we have developed a microp
 hysical model that describes the evolution of backstresses during deformat
 ion over a wide range of timescales. Here we describe and validate this mo
 del using a range of laboratory experiments that include multianvil compre
 ssion at a synchrotron\, high-temperature uniaxial creep\, constant-load n
 anoindentation\, and high-strain-rate impact. This model provides a new fr
 amework for interpreting seismological and geodynamic observations in term
 s of the density of dislocations and suggests that spatial variations of d
 islocation density in Earth's interior may be more important in some situa
 tions than other state variables such as water activity or melt content.
LOCATION:Wolfson Lecture Theatre
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