Abstract:

In this paper, the global topography, the depth of the Moho(the cxustalmodel CRUST2.0)，th a depths ofupper mantle discontinuities were analyzed using the spherical harmonics. Based on these data, the spatial large scaledistribution information has been obtained by sacking the first 4 degree modes, and the main energy distributionshave been understood by synthesizing the four items with the maxunal squares of amplitudes. The results show thatthere exiss a large scale asynrrnetry on the scale of semisphere in the topographies of the Moho and the‘410'discontinuities, and the asynrrnetry character of the nor-tl}rsouth semispheres is more obvious than that of the westeast semispheres; However, there exiss a scale asymmetry on the small side in the topographies of‘520' and‘660'discontinu ides, instead of such a large sphere scale asynrrnetry.

Key words: spherical harmonic analysis, Moho, upper mantle discontinuities, asymmetry