Normal fault growth in layered basaltic rocks: the role of strain rate in fault evolution

This is a Preprint and has not been peer reviewed. The published version of this Preprint is available: https://doi.org/10.1016/j.jsg.2018.07.017.

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Authors

Alodie Bubeck , Richard Walker , Jonathan Imber, Chris MacLeod

Abstract

Conceptual models for the evolution of dilatant faults in volcanic rift settings involve a step-wise growth pattern, involving upward propagation of subsurface faults, surface monocline formation, which are breached by subvertical, open faults. Immature, discontinuous normal faults are considered representative of the early stages of mature, linked faults that accommodate extensional strains. We consider the evolution of surface-breaching normal faults using a comparison of the distribution and geometry of normal faults from two volcanic rift zones: the Koaʻe fault system, Hawaiʻi, and the Krafla fissure swarm, NE Iceland. Field mapping highlights similarities to current predicted geometries, but also prominent differences that are not reconciled by current models. Variable deformation styles record magma supply changes within the rift zones, which drive local strain rate gradients. Building on existing studies, we present a conceptual model of fault growth that accounts for spatial and temporal changes in strain rate within the deforming regions. We propose that faults in separate rift systems may not advance through the same stages of evolution and that faults within individual rift systems can show differing growth patterns. Variations in surface strains may be indicative of subsurface magmatic system changes, with important implications for our understanding of volcano-tectonic coupling.

DOI

https://doi.org/10.31223/osf.io/zmt54

Subjects

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

Keywords

normal fault, extension, monocline, Basalt, dilatant fault, volcanic rift

Dates

Published: 2017-10-30 11:56

Last Updated: 2018-07-27 10:49

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License

CC BY Attribution 4.0 International

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