A new model for fault growth during syn-kinematic deposition

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Emma K Bramham, Tim J. Wright, Douglas Paton


Constraining the mechanisms of fault growth is essential for understanding extensional tectonics. In these dynamic systems the propagation of existing faults through recent syn-kinematic depositions is a poorly understood yet critical process. To understand how underlying structures influence faulting, we examine fault growth in a 10 kyr magmatically-resurfaced region of the Krafla fissure swarm, Iceland. We use a high-resolution digital (0.5 m) elevation model derived from airborne LiDAR to measure 775 fault profiles, with lengths ranging from 15 m to 2 km. For each fault, we measure the ratio of vertical displacement to length (Dmax/L) and the proportion of the fault that is un-displaced (“fissure-like”). We observe that many shorter faults (<200 m) retain fissure-like features with no vertical displacement for substantial parts of their displacement profiles; longer faults (> 200 m) are typically fully displaced and have Dmax/L at the upper end of the global population. We hypothesize that faults initiate at the surface as fissures in resurfaced material as a result of flexural stresses caused by displacements on underlying faults. Faults then accrue vertical displacement following a constant-length model and only grow by linkage or lengthening when they reach a classically-shaped displacement-length profile. This hybrid growth mechanism is repeated with the deposition of each subsequent syn-kinematic layer resulting in a remarkably wide distribution of Dmax/L. Whilst our observations are directly associated with magmatic resurfacing process, our results capture a specific period in the fault slip-deposition cycle that is equally applicable to fault zone characterization in sedimentary basins.




Earth Sciences, Geology, Physical Sciences and Mathematics, Tectonics and Structure


Iceland, Extensional, Fault growth, Krafla, Mid Atlantic Ridge, syn-kinematic


Published: 2020-02-04 13:55

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CC BY Attribution 4.0 International

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