Velocity-Dependent Friction and Its Role in the Evolution of Surface Deformation and Topography in Strike-Slip Fault Systems

Strike-slip faults accommodate plate motion through a coupled spectrum of abrupt seismic rupture and distributed, aseismic creep that coexist and interact within the same fault system. Yet the surface expression of these behaviours remains poorly constrained, largely because the short-term physics of frictional instability and the long-term construction of fault-zone morphology are rarely observed within a single framework. Here, we address this gap using seismotectonic analogue experiments designed to isolate how velocity-dependent (velocity-weakening and velocity-strengthening) and neutral frictional regimes govern both transient and cumulative deformation in strike-slip systems. The experiments reproduce hundreds of analogue earthquake cycles along a laboratory strike-slip fault system to build topography while simultaneously measuring shear force, acoustic emissions, and full-field surface displacements. By systematically modifying fault material properties and boundary conditions, we analyse their mechanical and geometric consequences.

We argue that the distinction between velocity-weakening, neutral, and strengthening friction is not merely a control on whether earthquakes occur but also organizes fault-zone architecture. In the velocity-weakening zone, deformation is expected to concentrate episodically into narrow, migrating shear bands that imprint discontinuous, step-like surface relief. In contrast, velocity-strengthening and velocity-neutral regimes should promote diffuse surface strain, topographic gradients, and a cumulative memory of stable slip. Investigating the interaction between these regimes provides a mechanical explanation for natural strike-slip faults that often display coexisting seismic segments and creeping sections. By linking fault frictional heterogeneity to measurable surface deformation patterns, we aim to contribute to presenting a mechanical and morphological framework for strike-slip fault evolution.