Recurrent aseismic deformation transients, sometimes accompanied by deep non-volcanic tremors, have been observed in shallow subduction zones, transform plate boundaries and mega-landslide faults. They pose significant questions as to their origin, and the existing concepts of interseismic loading on the locked seismogenic zone. In the numerical modeling of subduction earthquake sequences, we found that aseismic deformation transients emerge as a natural outcome of the rate- and state-dependent frictional processes revealed in laboratory fault-sliding experiments. Transients can occur near the down-dip end of the seismogenic zone, and propagate along the strike, in 3D studies, with heterogeneous stresses in the down-dip region. When the fluid pore pressure is near-lithostatic around and further down-dip from the velocity-weakening-to-strengthening stability transition, the system exhibits self-sustained short-period (several months to a few years) aseismic oscillations, with lab values of the characteristic slip distance. Evidence that such fluid pressure conditions may actually be present is independently provided by the occurrence of non-volcanic tremors as apparent responses to extremely small (< 0.01 MPa) stress changes, and by petrological constraints on the expected regions of metamorphic dehydration in shallow-dipping subduction zones, such as the northern Cascadia, SW Japan and Guerrero, Mexico. Transient sequences can also be triggered by a step-like interseismic stress perturbation on the subduction fault, due to extensional earthquakes in the descending slab, or to pore pressure changes, e.g., during episodes of metamorphic fluid release. Properties of triggered transients and future thrust earthquakes depend on the interseismic time when the perturbation is introduced, its relative location along the thrust interface, and its magnitude.