| Aseismic processes, including slow earthquakes and other, tectonically induced deformations, are sometimes associated with large earthquakes. They can involve large mass movements, which in turn change the inertia tensor of the Earth, potentially exciting variations in Earth's rotation. Since the mid-1970's, many investigators have stressed the point that aseismic slip could play an important role in maintaining the Chandler wobble, because such processes occur over time intervals that are short compared with the Chandler wobble period.; We have attempted to quantify the actual influence of aseismic deformation on the Chandler wobble during this century. We assumed that the aseismic slip event has the same fault mechanism as that of the associated earthquake. All aseismic moments are taken to be amplified relative to their associated seismic moment by some multiplicative factor. We also assumed that each aseismic event possesses a ramp source-time function extending over the duration of the aseismic activity. Under these assumptions, we used a modified normal mode approach to calculate the global deformation and implied change in the Earth's inertia tensor from various aseismic deformation events.; We find that there is an optimal value of the aseismic rise time, six months, for most events in the subduction zones. Based on the 6-month aseismic rise time, we have inferred amplification factors from actual polar motion and polar motion excitation time series. The values of the amplification factors range from 30 to 80,000; however, the total change in the inertia tensor components for each aseismic plus its associated seismic event is consistently {dollar}10sp{lcub}28{rcub}{dollar} to {dollar}10sp{lcub}29{rcub}{dollar} kg m{dollar}sp2.{dollar} This suggests that the total moment released in most subduction zones around the world may be the same order of magnitude.; Our modeling of the aseismic deformation suggests that aseismic (tectonic) deformation is a major source for maintaining the Chandler wobble. We believe that aseismic deformation can account for more than 50% of the excitation of the Chandler wobble. |
