HR: 0830h
AN: S21E-0345    [PDF]
TI: Modeling Shear Instabilities With Block Sliders: Brittle and Ductile
AU: * Riedel, M R
EM: miker@geo.uni-potsdam.de
AF: University of Potsdam Institute of Geosciences, Karl-Liebknecht-Strasse 24, Golm, D-14476 Germany
AB: Block slider-type models have been succesfully used for almost 35 years to describe the spatio-temporal development of shear instabilities in the brittle crust (Burridge \& Knopoff, 1967; Olami et al., 1992). More recently, increasing attention is paid on the extension of the classical Burridge-Knopoff model (based on a pure Mohr-Coulomb rheology) with a viscous component, either to include depth-dependent properties into the model or aiming at a more accurate description of fore- and aftershock sequences of a main earthquake event (e.g. Hainzl et al., 1999). On the other hand, viscous feedback mechanisms of various types have become an increasingly attractive mechanism for the generation of intermediate-depth and deep-focus earthquakes in the ductile mantle lithosphere (e.g. Wiens \& Snider, 2001). Heat generated during viscous deformation provides a positive feedback to creep and eventually faulting under high pressure (Karato et al., 2001, Bercovici \& Karato, 2003). The present paper discusses the specific properties of block slider-type models that are extended with a viscous component and compare their behaviour with the pure brittle ("classical") case. Block slider-type models for ductile instabilities are numerically much less demanding than solutions based on the corresponding, thermal-mechanically coupled, continuum equations. They allow for the inclusion of possible non-equilibrium effects associated with mineral phase transformations in a subducting slab (kinetic overshoot, grainsize reduction, latent heat release) in a straightforward manner. They may therefore serve as an effective tool to study the coupling of viscous heating, temperature-dependent viscosity and brittle stress transfer that are thought to cause the specific spatial-temporal clustering of intermediate-depth and deep-focus eartquakes. References D. Bercovici and S. Karato "Theoretical Analysis of Shear Localization in the Lithosphere", in: Reviews in Mineralogy and Geochemistry 51, eds. S. Karato and H.-R. Wenk, Chapter 13 (2003) 387-421 R. Burridge and L. Knopoff "Model and theoretical seismicity", Bull. Seism. Soc. Am. 57 (1967) 341-371 S. Hainzl and G. Z\"oller and J. Kurths "Similar Power-Laws for Fore- and Aftershock Sequences in a Spring-Block Model for Earthquakes", J. Geophys. Res. 104 (1999) 7243-7253 S. Karato, M. R. Riedel, D. A. Yuen, "Rheological Structure and Deformation of Subducted Slabs in the Mantle Transition Zone: Implications for Mantle Circulation and Deep Earthquakes", Phys. Earth Planet. Inter. 127 (2001) 83-108 Z. Olami and H. J. S. Feder and K. Christensen "Self-organized criticality in a continuous, nonconservative cellular automaton modeling earthquakes", Phys. Rev. Lett. 68 (1992) 1244-1247 D. A. Wiens and N. O. Snider "Repeating Deep Earthquakes: Evidence for Fault Reactivation at Great Depth", Science 293 (2001) 1463-1466
DE: 7218 Lithosphere and upper mantle
DE: 7230 Seismicity and seismotectonics
DE: 7260 Theory and modeling
DE: 8120 Dynamics of lithosphere and mantle--general
DE: 8123 Dynamics, seismotectonics
SC: Seismology [S]
MN: 2003 Fall Meeting