HR: 1330h
AN: S22A-0409    [PDF]
TI: Stress Magnitudes in Asia and North America: Implications for Strength Profiles
AU: * Klein, E C
EM: elliot@mantle.geo.sunysb.edu
AF: Department of Geosciences, Stony Brook University, Stony Brook, NY 11794-2100 United States
AU: Flesch, L M
EM: flesch@dtm.ciw.edu
AF: Department of Terrestrial Magnetism, Carnegie Institution of Washington, Washington, DC 20015 United States
AU: Holt, W E
EM: wholt@mantle.geo.sunysb.edu
AF: Department of Geosciences, Stony Brook University, Stony Brook, NY 11794-2100 United States
AU: Wen, L
EM: Lianxing.Wen@sunysb.edu
AF: Department of Geosciences, Stony Brook University, Stony Brook, NY 11794-2100 United States
AU: Haines, A
EM: haines@esc.cam.ac.uk
AF: Bullard Laboratories, University of Cambridge, Cambridge, CB3 0EZ United Kingdom
AB: We present dynamic models that incorporate lithospheric gravitational potential energy (GPE), coupling with deeper mantle circulation, and stress field boundary conditions. Our integrated modeling approach allows us to quantify the degree of coupling between the lithosphere and the mantle in western North America and throughout southern and central Asia. Although both regions undergo active continental deformation in broad diffuse zones, the relative roles of the forces contributing to the deformation of each region differ. In order to quantify the forces responsible for the continental deformation we estimate the contributions of lithospheric GPE, stresses associated with plate motions, and basal tractions resulting from mantle-lithosphere coupling. Internal density distributions inferred using seismic tomography and history of subduction drive our mantle circulation model that is constrained to match the geoid, topography, and plate motions. Our lithospheric models are solutions to equations for a thin sheet, with basal traction contributions, and allow us to solve for both the vertically averaged magnitudes and styles of the total deviatoric stress field that drives continental deformation. Initially we determine a kinematic strain rate and velocity field model based on interpolation of GPS velocity vectors and Quaternary strain rates. Results to date are consistent with significant coupling between lithosphere and deeper mantle circulation throughout deforming Asia. On the other hand, our results require a significant decoupling between deeper mantle circulation and the lithosphere in western North America. The magnitudes of vertically averaged deviatoric stress range from 5-40 MPa in Asia, and 5-20 MPa in western North America. We next use the magnitudes of the vertical averages of stress to investigate how strength is partitioned within the lithosphere. Assuming Byerlee friction for the brittle portion of the lithosphere and flow laws for the rheology of regions below, we investigate the regional variations in thickness of the brittle, frictional portion of the lithosphere and compare this with the depth of seismicity. Results to date suggest that 50% or more of the lithospheric strength is contained within the brittle, seismogenic portion of the lithosphere.
DE: 8120 Dynamics of lithosphere and mantle--general
DE: 8159 Rheology--crust and lithosphere
DE: 8164 Stresses--crust and lithosphere
DE: 9320 Asia
DE: 9350 North America
SC: Seismology [S]
MN: 2003 Fall Meeting