Defect microdynamics in minerals and solid‐state mechanisms of seismic wave attenuation and velocity dispersion in the mantle

Abstract

The propagation of seismic waves in the Earth's seismic wave velocities [Kanamori and Anderson, 1977]. The attenuation of seismic waves and the associated velocity dispersion in rocks are likely to be due to 1Now at Department of Geology and Geophysics, University of Minnesota, Minneapolis.relaxation process(es). In many cases these processes involve the motion of defects (including melts) in rocks, and therefore Earth's internal friction and velocity dispersion depend on the concentration, geometry, and mobility of relevant defects [e.g., Jackson and Anderson, 1970]. These defect-related properties are known to be sensitive to the thermochemical environment (temperature, pressure, fugacity of oxygen and water, etc.) and the differential stress, both of which are also closely related to tectonic activity. Therefore the observed seismic wave attenuation (and velocity anomalies), if properly interpreted, can provide important clues to Earth's thermochemical and stress states. The principal aim of

Elastic and anelastic anomalies in (Ca,Sr)TiO3 perovskites: Analogue behaviour for silicate perovskites

“…, Karato and Spetzler, 1990) and are substantially smaller , Harrison and Redfern, 2002;Lemanov et al, 2002). RUS data should therefore provide an additional perspective on dispersion with respect to both frequency and stress for anelastic effects due to twin wall motions.…”

Simulation of screw dislocations in wadsleyite

“…These one-dimensional extended defects can also contribute to seismic dispersion and attenuation (Jackson, 2007;Karato and Spetzler, 1990) and provide pathways for rapid diffusion of trace and major elements into and out of the interior of minerals. Many of the properties of dislocations can be understood in terms of imperfections in an elastic continuum but others, such as their mobility and effect on diffusivity, are determined entirely by the detailed atomic scale structure of the dislocation core.…”

Elastoviscoplastic micromechanical modeling of the transient creep of ice

“…One can evoke for example the postseismic deformations in fault regions due to the viscoelastic behavior of the lower crust and/or the upper mantle [Kenner and Segall, 2000;Barbot et al, 2008], the uplift of continents associated to postglacial rebound [Yuen et al, 1986], the size-dependent relaxation of impact basin on the Moon and on Mars [Mohit, 2008], the attenuation of seismic waves associated to viscous dissipation along the travel path of the wave [Karato and Spetzler, 1990], and more generally all situations in which the mechanical response of the material involves both elasticity and viscoplasticity. For ice, transient effects associated to the elastoviscoplastic behavior should be encountered when ice flow changes direction rapidly, such as for glaciers flowing above irregular bed rocks or for sea ice coming up against an offshore rig.…”