Frictional Characteristics of Oceanic Transform Faults: Progressive Deformation and Alteration Controls Seismic Style

Oceanic transform faults are inferred to be weak relative surrounding oceanic crust and primarily slip aseismically. Neither their weakness nor tendency creep well-explained. We test the effects of fault-rock evolution on fault frictional strength stability using direct-shear experiments (at room temperature, 10 MPa normal stress, fluid-saturated conditions) dolerite from East Pacific Rise natural rocks exhumed Southern Troodos Transform, Cyprus. Dolerites cemented breccias frictionally strong (? = 0.52–0.85) velocity-weakening (strength decreases with increasing velocity, characteristic earthquakes). In contrast, matrix-rich chlorite-bearing gouges 0.25–0.48) velocity-strengthening (characteristic stable creep). This transition implies that seismic behavior is controlled by degree damage alteration, such earthquakes can nucleate within relatively intact crust, whereas segments increased chlorite content tend