Rupture to the trench? Frictional properties and fracture energy of incoming sediments at the Cascadia subduction zone

•High velocity friction experiments were performed on Cascadia input sediments.•Cascadia results compared to literature compilation to assess gouge behavior.•Fracture energy (Wb) of wet gouges significantly lower than dry gouges or rocks.•Wb of Cascadia sediments order of magnitude larger than other subduction margins.•Shallow coseismic slip on Cascadia décollement potentially inhibited by high Wb.