Laboratory Earthquake Ruptures Contained by Velocity Strengthening Fault Patches

Many natural faults are believed to consist of velocity weakening (VW) patches surrounded by velocity strengthening (VS) sections. Numerical studies routinely employ this framework to study earthquake sequences including repeating earthquakes. In this laboratory study, we made a VW asperity, of length L, from a bare Poly(methyl methacrylate) PMMA frictional interface and coated the surrounding interface with Teflon to make VS fault sections. Behavior of this isolated asperity was studied as a function of L (ranging from 100 to 400 mm) and the critical nucleation length, h∗ ${h}^{\ast }$, which is inversely proportional to the applied normal stress (2–16 MPa). Consistent with recent numerical simulations, we observed aseismic slip for L/h∗ $L/{h}^{\ast }$