CSDMS 2014 annual meeting poster Jean-Arthur Olive
The long-term evolution of normal faults controlled by lithospheric flexure and surface processes.
Mark Behn, WHOI Woods Hole Massachusetts, United States. mbehn@whoi.edu
Abstract:
We investigate the growth of normal faults on long timescales (10-1000 kyrs) and seek to identify key mechanical controls on fault dip, lifespan, and related topography. To do so, we consider the energy budget of a growing fault, which is partitioned into 1/ overcoming the frictional resistance on the fault and 2/ sustaining the build-up of topography and associated flexure. Our model builds on classic finite extension theory, but incorporates the possibility that the active fault plane may rotate as a response to the accumulation of flexural stresses with increasing extension. We postulate that fault plane rotation acts to minimize the amount of extensional work required to keep the fault active. In an elastic layer, this assumption results in rapid rotation of the active fault plane from ~60° down to 30–40° before fault heave has reached 40% of the faulted layer thickness. In our model, fault rotation rates scale as the inverse of the faulted layer thickness, which is in quantitative agreement with 2D geodynamic simulations that include an elasto-plastic description of the lithosphere. We show that fault rotation promotes longer-lived fault extension compared to continued slip on a high angle normal fault, and therefore holds a strong control on faulting styles (i.e., multiple short-offset vs. dominant large-offset faults). Finally, we incorporate erosion and deposition processes into the model, which locally enhance or relieve a portion of the topographic load, and characterize their influence on the evolution of extensional systems.
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