Efforts to understand the mechanisms that lead to earthquakes in subduction zones involve theoretical and numerical modeling studies, laboratory measurements of the deformation of geological materials in response to changes in stress leading up to, during and after earthquakes and related 'slow slip' events, as well as active monitoring of seismic activity in subduction zones using arrays of seismometers. A new and under-explored possibility is using magnetotelluric (MT) measurements of changes in the geoelectric and geomagnetic field at ground level by deploying arrays of MT instruments within subduction zones to detect subtle changes in the micro-scale networks of fluids that exist within the rock formations near the subducting plate. These changes, if detectible using this method, may provide a new window into the deformation of the rocks and minerals prior to, during and after earthquakes within the subduction zone. Such information would contribute to our understanding of mechanisms that lead to subduction earthquakes, and potentially could assist with efforts to provide more accurate assessments of seismic hazards.