Stochastic Modeling of Small-Scale, Anisotropic Structures in the Continental Upper Mantle,

摘要: Abstract : New methods for the analysis of three-component seismograms have been applied to data from both continental and oceanic regions. Polarization anisotropy, manifested as splitting surface, guided, shear body waves, has observed in all regions, but no significant azimuthal anisotropy detected. This is expected if local orientation olivine crystals upper mantle incoherent on scale path lengths used these experiments (Delta = 35 deg - 50 deg). From a detailed study trans-Australia paths, we shown that shear-wave western Australia craton averages 3-4% uppermost mantle, it terminates abruptly at Lehmann (L) discontinuity near depth 250 km. Our physical interpretation L beneath ancient cratons marks transition an anisotropic mechanical boundary layer more isotropic region thick tectosphere. Above L, temperatures evidently remained cold enough freeze-in small-scale structures tectonic fabrics generated episodes orogenic compression associated with tectospheric stabilization. Below such were either never or annealed out subsequent their formation. These hypotheses about subcontinental structure considerable bearing diverse set geological geodynamical problems, ranging formation kimberlite vulcanism.