Graben Formation and Dike Arrest during the 2009 Harrat Lunayyir Dike Intrusion in Saudi Arabia: Insights from InSAR, Stress Calculations and Analog Experiments
KAUST DepartmentPhysical Sciences and Engineering (PSE) Division
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AbstractDetailed spatial and temporal accounts of propagating dikes from crustal deformation data, including their interplay with faulting, are rare, leaving many questions about how this interplay affects graben formation and the arrest of dikes unanswered. Here we use InSAR observations, stress calculations and analog experiments to investigate the interaction between an intruding dike and normal faulting during the 2009 Harrat Lunayyir dike intrusion in western Saudi Arabia. We generated five displacement maps from InSAR data to unravel the temporal evolution of deformation covering the majority of the intrusion. We find that the observed surface displacements can be modeled by a ~2-m-thick dike with an upper tip ~2 km below the surface on 16 May 2009, four weeks after the onset of seismic unrest. In the following three days, the dike propagated to within ~1 km of the surface with graben-bounding normal faulting dominating the near-field deformation. The volume of the dike doubled between mid-May and mid-June. We carried out analog experiments that indicate that the wedge-shaped graben grew outwards with the faulting style changing progressively from normal faulting to oblique. Coulomb failure stress change calculations show that the intruding dike caused two zones of shallow horizontal tension on both sides of the dike, producing two zones of fissuring and normal faulting at the surface. In return, the faulting provoked compression around the upper tip of the dike, holding back its vertical propagation.
CitationGraben Formation and Dike Arrest during the 2009 Harrat Lunayyir Dike Intrusion in Saudi Arabia: Insights from InSAR, Stress Calculations and Analog Experiments 2016:n/a Journal of Geophysical Research: Solid Earth
SponsorsWe thank Samantha Hansen (Univ. Alabama) for earthquake locations and Luigi Passarelli (GFZ) for useful discussions. We thank the associate editor Mike Poland and two anonymous reviewers for helpful comments. The SAR images were provided by the European Space Agency (ESA) through the Category-1 project #6703. The GMT software (Wessel and Smith 1998) was used to prepare Fig. 1. The research reported in this publication was supported by King Abdullah University of Science and Technology (KAUST). ER and FC were funded by the European Union through the ERC StG Project CCMP-POMPEI, grant N. 240583.