Several lines of evidence suggest that there are subtle geodetic signals that can be interpreted to gain information about the range of earthquake cycle behavior and rheology of the lithosphere. Moderately sized (Mw<7.0) silent earthquakes slipping rates too slow to cause significant shaking and have been widely observed in the Cascadia and Nankai subduction zones. We have shown the predicted signature of great (Mw>7.5) silent earthquakes may be quite different from that of the moderately sized events and that the pervasive observation of partially coupled fault interfaces may in fact be the signature of great silent earthquakes occur over hundreds of years. To understand the behavior of deeper lithosphere we are using both geologic and geodetic observations to develop models that explain all phases of earthquake cycle deformation using extended linear rheologies. The remarkable correlation between geologic and geodetic slip rate estimates leads of a view of the earthquake cycle as far more steady than classical Maxwell models predict, requiring high-resolution fault system models to image these subtle, yet important, behaviors.