TOROIDAL POLOIDAL PARTITIONING OF GLOBAL POSTSEISMIC DEFORMATION/

An Earth model subject to dislocations is studied in order to investig ate the toroidal/poloidal content of global post-seismic deformation. Differently from previous analyses, our approach allows us to deal wit h some of the main complexities of the real Earth, such as sphericity, self-gravitation, and theological stratification. The time-dependent ratio between toroidal and poloidal displacements is evaluated in the near and far-field of both strike and dip-slip lithospheric sources ch aracterized by a finite length. Our findings show that post-seismic de formation changes its nature from poloidal to toroidal (and viceversa) on time-scales of several decades and over distances comparable with the dimensions of the lithospheric plates. The effects on horizontal v elocities in North America of both poloidal and toroidal components in duced by the Alaska 1964 earthquake is comparable with the signatures due to postglacial rebound; these two geodynamical phenomena, are curr ently detectable by variations along baselines connecting VLBI station s.