How Do Rift-Related Fault Network Distributions Evolve? Quantitative Comparisons Between Natural Fault Observations and 3D Numerical Models of Continental Extension

Continental extension is primarily accommodated by the evolution of normal fault networks. Rifts are shaped by complex tectonic processes and it has historically been difficult to determine the key rift controls using only observations from natural rifts. Here, we use 3D thermo-mechanical, high-resolution (<650 m) forward models of continental extension to investigate how fault network patterns vary as a function of key rift parameters, including extension rate, the magnitude of strain weakening, and the distribution and magnitude of initial crustal damage. We quantitatively compare modeled fault networks with observations of fault patterns in natural rifts, finding key similarities in their along-strike variability and scaling distributions. We show that fault-accommodated strain summed across the entire 180 x 180 km study area increases linearly with time. We find that large faults do not abide by power-law scaling as they are limited by an upper finite characteristic, omega(0). Fault weakening, and the spatial distribution of initial plastic strain blocks, exert a key control on fault characteristics. We show that off-fault (i.e., non-fault extracted) deformation accounts for 25%-45% of the total extensional strain, depending on the rift parameters. As fault population statistics produce distinct characteristics for our investigated rift parameters, further numerical and observational data may enable the future reconstruction of key rifting parameters through observational data alone.

Automated summary

The article investigates the relationship between fault network patterns and key rift parameters in continental extension using 3D thermo-mechanical models. The study reveals key characteristics of fault patterns and highlights the importance of fault weakening and spatial distribution of initial plastic strain blocks in controlling fault characteristics.