French, Melodie E.Condit, Cailey B.2019-10-232019-10-232019French, Melodie E. and Condit, Cailey B.. "Slip partitioning along an idealized subduction plate boundary at deep slow slip conditions." <i>Earth and Planetary Science Letters,</i> 528, (2019) Elsevier: https://doi.org/10.1016/j.epsl.2019.115828.https://hdl.handle.net/1911/107487Below the base of many subduction seismogenic zones, the plate interface periodically slips at rates 1 to 2 orders of magnitude faster than tectonic plate velocities. A number of competing hypotheses exist to explain the mechanisms for these slow slip events (SSEs), but they remain incompletely tested because we do not know how deformation is partitioned across the lithologically complex plate boundary interface. We use the deepest exposure of the Arosa zone, a ∼520 m-thick exhumed subduction interface, as a case study to evaluate the partitioning of strain between lithologic units throughout the SSE cycle. We review and synthesize published constitutive relations for the five lithologic units present to express shear stress as a function of deformation rate. We use these results to predict (1) the shear stress across the plate boundary as a function of slip velocity and (2) the partitioning of deformation among the different lithologic units for SSE and aseismic creep velocities. We conduct this analysis for pore fluid pressures from hydrostatic to near-lithostatic. Our results show that, at pore fluid pressure close to hydrostatic, aseismic creep and SSE velocities occur by viscous deformation of calcareous and quartzose units. However, once the pore fluid pressure increases above 80% of lithostatic, plate boundary slip migrates from the calcareous and quartzose rocks during aseismic creep to frictional deformation of talc schist during slow slip. This result is insensitive to differences in the thicknesses of metasedimentary units that may be present along subduction plate boundaries and, therefore, may apply to subduction plate boundaries in general.engThis is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/)Journal articlefault mechanicsrheologysubductionslow slip eventshttps://doi.org/10.1016/j.epsl.2019.115828