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Xanthippi Markenscoff

“Volume Collapse” Instabilities in Deep Earthquakes: A Shear Source Nucleated and Driven by Pressure"

Event Details:

Thursday, February 9, 2023
4:30pm - 5:30pm PST

Location

Bldg. 530 rm 127

Abstract: Under a high critical pressure, and in full isotropy, a collapsing volume breaks the symmetries and in successive instabilities it nucleates and expands planarly (as a densified “pancake-like” inclusion) emitting the radiation of a shear source (double couple in seismology), as the only possible way to radiate the energy out under high pressure. The instabilities allow the minimization of the energy spent to move the boundary of phase discontinuity and minimize the interaction energy with the pre-stress (pressure) field. The deformation fields are those of the self-similarly expanding ellipsoidal inclusion with transformation strain (dynamic Eshelby problem) and the energetics of the moving phase boundary are governed by Noether’s theorem.  At the vanishing of the M integral a critical “nucleation” pressure is obtained at which an arbitrarily small inclusion nucleates and grows at constant potential energy driven by the pressure acting on the change in volume, while shear deformation is produced to accommodate the large collapsing volume in the thin inclusion. The solution is independent of scale, from the nano to the very large, where it provides the long-sought cause of the deep-focus earthquakes at 400-700 km in Earth’s mantle. The dynamic Eshelby problem is also valid for Newtonian fluids, and the obtained instabilities provide insight into phenomena ranging from failure waves to crystal-structural and amorphization transformations in laboratory experiments and planetary impacts.

Bio: Xanthippi Markenscoff obtained the Diploma of Civil Engineering at the National Technical University of Athens, Greece, and the Ph.D. degree at Princeton University. She has been an Asst Prof at Carnegie-Mellon University, Associate and Full Professor at UCSB, and Professor to Distinguished Professor in Mechanical and Aerospace Engineering at UCSD, now Emerita Recalled to service. She has held Visiting positions at Brown University, Harvard University, Ecole Polytechnique (Paris , France), Oxford University and was a Visiting Miller Professor (2003) and a Springer Professor (2008) at UC Berkeley. She is a Fellow of ASME and of SES and was awarded a Doctor Honoris Causa degree from the National Technical University of Athens, Greece.

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