HR: 1330h
AN: S22A-0410 [PDF]
TI: Rheology of the continental lithosphere
AU: * Turcotte, D L
EM: turcotte@geology.ucdavis.edu
AF: Department of Geology, University of California, Davis, CA 95616 United States
AB:
The deformation of the continental lithosphere is associated with a combination of ductile and brittle processes. Ductile
deformation is analyzed utilizing creep (Newtonian, non-Newtonian) and plastic rheologies. These can be extremely sensitive
to composition and temperature. In some cases elastic stresses are relaxed, but in other cases elastic stresses are preserved
over 108-109 years. The distinction between renewable stress (plate tectonic, bending) and nonrenewable (thermal, membrane)
must be made. The concept of a yield stress is blurred. Brittle deformation tends to be much more complex. Displacements on
faults certainly play an important role, but faults are present at all scales. Under some circumstances it is appropriate to
treat these deformations in a continuum manner. An avenue for doing this is damage mechanics. The concept of damage mechanics
have been utilized widely in engineering problems. We show that when damage mechanics is applied to the brittle deformation
of the upper continental crust, a non-Newtonian, power-law viscous rheology is derived. There is a well defined yield stress
that can be associated with the dynamic coefficient of friction. Below this stress the upper crust behaves elastically and
can act as a stress guide. Above the yield stress the continuum deformations can be modeled as a power-law viscous fluid
(with exponent,l 10). This behavior is associated with aftershock sequences. A main shock suddenly increases the stress in
regions of the upper crust. Stress relaxation is accomplished by the aftershock sequence and OmoriÝs law for the decay of
aftershocks quantifies the relevant fluid rheology.
DE: 1236 Rheology of the lithosphere and mantle (8160)
DE: 5102 Acoustic properties
DE: 5104 Fracture and flow
DE: 7218 Lithosphere and upper mantle
DE: 8164 Stresses--crust and lithosphere
SC: Seismology [S]
MN: 2003 Fall Meeting