In the past half century several articles have described a correlation between global seismic productivity and fluctuations in the spin rate of the Earth. The utility of the observed correlation is that a reduction in earth's spin rate apparently precedes changes in seismicity by about five years, with potential contributions to forecasting future earthquakes. Proposed mechanisms range from reducing Earth’s oblateness during periods of slow spin (maximum length of the day) with consequent changes in surface strain, to decelerating the mantle resulting in weak plate boundaries forces arising from the arrested momentum of overlying plates. These forces can be shown to be many orders of magnitude too small to trigger earthquakes. A long-neglected mechanism linking north-south lithospheric forces to Earth's shape exists in the form of Polflucht, the acceleration invoked in 1915 by Wegener in an unsuccessful attempt to explain the motion of continents. The acceleration depends on the oblateness of the Earth (J2) which is influenced by spin rate and mass distribution. Changes in Polflucht amplitudes are calculated to exceed 20 µbar on some east-west transforms, potentially retarding the nucleation of critically stressed earthquakes at times of maximum J2 and simultaneously advancing the timing of earthquakes in NW or NE striking transforms, or east-west striking subduction zones. The calculated stress changes remain more than order of magnitude smaller than those hitherto associated with earthquake triggering, yet their statistical influence on the timing of global seismicity is many orders of magnitude larger than previously proposed mechanisms linking Earth's rotation to lithospheric seismicity.