The unique anisotropy of the Pacific upper mantle

摘要: The development and interpretation of tomographic models the Earth's mantle have usually proceeded under assumption that fast slow seismic velocity anomalies represent a spatially heterogeneous temperature field associated with convection. Implicit in this approach is an either effect anisotropy on velocities small comparison isotropic thermal or compositional effects, results average heterogeneity, even if individual observations are affected by anisotropic structure. For example, upper portions oceanic commonly interpreted terms progressive cooling1,2 (and localized reheating3) amechanical boundary layer consisting rigid lithosphere underlying, less viscous, asthenosphere. Here, however, we present from global three-dimensional model shear-wave which shows uppermost beneath central Pacific Ocean considerably more complicated than simple model. Over broad area, its centre near Hawaii, data reveal regional anomaly elastic produces variations at least as large those due to effects. Because indicator strain Earth materials, our canbe used put constraints both buoyancy forces (thermal effects) flow patterns mantle.