Is the asthenosphere electrically anisotropic?

摘要: Abstract Two techniques for resolving the conductance of an electrically conductive asthenosphere are presented. The first technique combines observatory electromagnetic data in period range daily variation and longer, which provides penetration depths 400 km deeper, with laboratory conductivity upper mantle materials. can be estimated by this technique, but geometry - e.g. exact depth is not resolved. second extends classical magnetotelluric (MT) tensor estimation decomposition to 1000–30 000 s. If electrical exists, then field penetrates into it (1000 s) also through (30 000 s). concept regional strike directions has been successfully used obtain crustal anisotropy again employed at these long periods. surprising result that a strong directional dependence occurs. Although large arrays will necessary order prove really asthenosphere, results from 100–200 extent encouraging. superposition explains some why earlier determinations had little success: only fortunate case where MT experiment was performed parallel direction conductor, asthenospheric one, structure Electrical uppermost supports intracrystalline water, allows contribution hydrogen diffusity olivine: highly anisotropic respect crystal axis, if crystals partly aligned, measured direction-dependent.