In a recent issue of Eos, Florindo et al.  suggest that large seismic events, such as the magnitude 9.3 Sumatra earthquake of 26 December 2004, may cause changes in topography at the core-mantle boundary (CMB), thereby affecting flow in the core. They hypothesize that this effect may trigger a geomagnetic jerk, which would be observed at Earth's surface after a time delay to allow for the signal to propagate through the weakly conducting mantle. However, they do not provide any estimates of the amplitude or form of the CMB topography changes that are required, or of the actual CMB deformation that may have occurred as a result of the Sumatra event.
Here, I argue that it is unlikely that large earthquakes can lead to geomagnetic jerks.