GP seminar speaker: Sylvain Barbot

06/07/2017 - 2:30pm to 3:30pm
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Sylvain Barbot 
Assistant Professor
Earth Observatory of Singapore
Nanyang Technological University

From Fault to Full Lithosphere Dynamics Modeling


Abstract: The last three decades have witnessed an explosion of
studies on fault processes, from kinematic modeling of geodetic data,
to dynamic modeling of fault rheology. These studies were made
possible by fundamental solutions that describe the stress and
displacements caused by slip on a fault (e.g., Okada, 1985, 1992). In
contrast, direct imaging of the kinematics of off-fault deformation is
still impractical, and the dynamic modeling of viscoelastic relaxation
or poroelastic rebound still relies on computationally intensive
numerical methods (e.g., Barbot & Fialko, 2010). As a result, much
less has been learned on the mechanics of deformation at plate
boundaries away from faults. Here, we describe a novel approach that
allows us to resolve distributed processes in kinematic inversions of
geodetic data and to incorporate off-fault deformation in numerical
models of earthquake cycles. We quantify analytically the displacement
and stress incurred by distributed inelastic strain in finite shear
zones (Barbot, Moore & Lambert, 2017). We use these elementary
solutions to simultaneously invert for slip on faults and distributed
strain in the surrounding rocks. Exploiting the rapid deformation that
followed the 2016 Mw 7.1 Kumamoto earthquake sequence, we directly
image the spatial distribution of the effective viscosity in the lower
crust, revealing low-viscosity regions aligned with the volcanic arc
and metamorphic provinces (Moore et al., 2017). Our formulation also
allows the dynamic simulation of earthquake cycles with distributed
deformation using the integral method, an approach many orders of
magnitude faster than the classic finite-element technique. We
simulate earthquakes cycles within the lithosphere-asthenosphere
system using rate-and-state friction and the power-law flow of olivine
(Lambert & Barbot, 2016), revealing the prevalence of viscoelastic
flow in the early stage of postseismic relaxation. To complement this
method, we describe how to reconcile short-term and long-term
tectonics during the 12Myr of the Indio-Eurasian collision. We show
earthquake cycles with boundary conditions compatible with balanced
cross section that include folding in the upper plate across axial
surfaces. Our approach will be instrumental in building comprehensive
physical models of stress evolution at plate boundaries.

For more information on this event, contact: 
Junle Jiang
Event Calendar: 
IGPP Conference Room (Munk 303)