Constraining Fracture Energies of Globally-observed Elongated Earthquakes by Physical-based Equation-of-motion of Rupture Tip

One of the main challenges for assessing future seismic hazards in both natural faults and gas fields is to estimate the time-dependent possible maximum earthquake magnitude. Largest natural or induced earthquakes, whose ruptures are confined by the seismogenic width or the reservoir thickness, usually develop a large aspect ratio (longer horizontally than vertically). Recent theoretical and numerical studies (e.g., Weng and Ampuero, 2019) show that rupture propagation on an elongated fault is predicted by an inertial equation-of-motion of rupture tip: F(Gc/G0)=M(v) a, where M(v) is a known function of rupture speed v, Gc and G0 are the fracture energy and energy release rate, and a=dv/dt is the rupture acceleration. Here, we extend this 3D theoretical rupture model from the uniform cases to a more general case that enables spatially heterogeneous conditions, such as along-strike variable fault width, along-strike, and along-depth stresses and friction properties. The essential input parameters that control rupture propagation and earthquake magnitude in 3D rupture model are the restored elastic energy that can be related to the seismic coupling models and the dissipated fracture energy, whose uncertainties are the largest. Here, we will report a new method to constrain the fracture energies of the globally observed elongated earthquakes by combining their kinematic slip models, moment rate functions, and the theoretical rupture-tip equation-of-motion. We will also discuss the possible scaling relation between fracture energy and fault slip observed at different fault locations. Constraining the fracture energies of global earthquakes will help us better understand the frictional behavior on natural faults and enables us to develop a practical model toward physics-based seismic hazard assessment for both natural and induced earthquakes.