THE POSSIBLE REFLECTION OF MANTLE DISCONTINUITIES IN PACIFIC GEOID AND BATHYMETRY

Geoid anomalies over the Pacific plate show lineated undulations appro ximately oriented in the direction of absolute plate motion. Conventio nal spectral analyses have revealed a broad range of dominant waveleng ths, but as filtering is direction-dependent, results are difficult to interpret. Here, we present a new approach designed to quantify the c orrelation between the geoid undulations and Pacific plate motion. We calculate the spatial correlation between geoid lineations and arbitra rily oriented, axisymmetric sinusoidal undulations of given wavelength . The pole (i.e., the orientation) of the sinusoid which maximizes the correlation is determined. The distance between this pole and the Pac ific hotspot pole is calculated and represents a measure of how well a geoid lineation of a given wavelength aligns with Pacific plate motio n. This distance varies with undulation wavelength and has discrete mi nima for several wavebands. These minima, moreover, occur at wavelengt hs whose values are remarkably close to the depths of seismically infe rred mantle discontinuities. A similar analysis of available bathymetr y corroborates these findings. If these correlations are significant, they suggest that geoid (and bathymetry) undulations are influenced by mantle structure and thus are likely to reflect mantle dynamics.