The structural relations of conjugate thrust faults and the master decollement imaged in a research-level, processed, multichannel seismic reflection record across the eastern Aleutian Trench allow quantitative estimates of the sediment strength and friction across thrust boundaries of the subduction zone. These estimates are derived from geometric relations between faults and from the overall geometry of accreted prisms. They suggest the presence of high pore-fluid pressures that result in low levels of friction along a master decollement and on the main bounding thrust faults in the accreted sediment. Therefore, coupling in the immediate trench area apparently does not contribute significantly to the generation of horizontal compression upslope.

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