Scaling Relations of Strike-Slip Earthquakes with Different Slip-Rate-Dependent Properties at Depth

Abstract

Abstract Empirical observations suggest that earthquake stress drop is generally constant. To investigate the effect of rupture width on earthquake scaling relations, we analyze synthetic seismicity produced by a 3D vertical strike-slip fault model using two different profiles of frictional slip-rate behavior below the seismogenic zone. Within the rate-and-state framework, a relatively abrupt transition of the a – b profile from velocity weakening to strengthening at the base of the seismogenic crust produces increasing slip and stress drop with increasing event size. Choosing a smoother transition allows large earthquakes to propagate deeper, leading to similar slip-length scaling but constant stress-drop scaling. Our numerical experiments support the idea that the maintenance of constant stress drop across the entire range of observed earthquake magnitudes may be achieved by allowing coseismic slip to rupture to depths below the seismogenic layer.