Preprints
https://doi.org/10.5194/egusphere-2024-852
https://doi.org/10.5194/egusphere-2024-852
28 Mar 2024
 | 28 Mar 2024
Status: this preprint is open for discussion.

The influence of vertical lithological contrasts on strike-slip fault behavior: Insights from analogue models

Sandra González-Muñoz, Guido Schreurs, Timothy Schmid, and Fidel Martín-González

Abstract. This work investigates the influence of rheological contrasts on the nucleation and behavior of strike-slip faults. To achieve this, we have carried out a series of brittle-viscous strike-slip shear analogue models, using quartz sand and microbeads as granular materials with different internal friction and cohesion values. Particle Imaging Velocimetry (PIV) was applied to time-series of surface images to calculate incremental and cumulative strains. Understanding how strike-slip faults nucleate and interact in the heterogeneous upper crust is relevant in seismic hazard analysis and geothermal and hydrocarbon exploration. To reproduce the heterogeneity of the upper crust, three sets of experiments we performed: 1) upper layer composed either of quartz sand or microbeads; 2) upper layer with a vertical contrast i.e., quartz sand surrounded by microbeads and vice-versa; and 3) same set-up as in the previous set but changing the orientation of the vertical contrast. Our study shows that the introduction of an upper crustal vertical contrast influences the behavior and evolution of strike-slip faults. The models containing a vertical contrast were more complex and induced a compartmentalization of the model. The initial fault strike is related to the material’s properties. However, this initial strike changes when faults crosscut the materials with less internal friction angle clockwise, and anticlockwise when the contrast has higher internal friction angle. Areas containing materials with less internal friction angle take longer to localized the deformation, but they show a greater number of faults. The biggest increase in the number of synthetic and antithetic faults occurs with the introduction of vertical contrast. These results were compared with the intraplate fault systems of the NW Iberian Peninsula, focusing on the Penacova-Régua-Verin and Manteigas-Vilariça-Bragança fault systems. They are major left-lateral faults that cross-cut lithologies characterized by vertical rheological contrasts, with deformation patterns similar to those observed in our analogue models.

Sandra González-Muñoz, Guido Schreurs, Timothy Schmid, and Fidel Martín-González

Status: open (until 17 May 2024)

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  • RC1: 'Comment on egusphere-2024-852', Roy H. Gabrielsen, 11 Apr 2024 reply
Sandra González-Muñoz, Guido Schreurs, Timothy Schmid, and Fidel Martín-González
Sandra González-Muñoz, Guido Schreurs, Timothy Schmid, and Fidel Martín-González

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Short summary
This work investigates the influence of vertical rheological contrasts on the nucleation and behavior of strike-slip faults, using analogue modelling. The introduction of rheological contrasts was achieved using quartz sand and microbeads grains. The study shows how the strike, type and evolution of the faults strongly depend on the characteristic of the lithology and its contact orientation. The results are comparable with the fault systems observed in the NW of the Iberian Peninsula.