Uploaded February 2016 | Updated September 2026, 10 hours ago
A simple (and hastily set up) model showing the orientations of normal and thrust faults formed within a single, mechanically-uniform sandpack. In this dry sand, faults form at ~30 degrees to sigma 1. Vertical sigma 1 during extension produces faults dipping 60 degrees, while horizontal sigma 1 during compression produces faults dipping 30 degrees. Normal faults are thus too steep to reactivate, and are overtaken by shallower faults that "shortcut" through pre-rift material. Mechanical contrast or rotation of existing normal faults would be necessary for reactivation.
A simple (and hastily set up) model showing the orientations of normal and thrust faults formed within a single, mechanically-uniform sandpack. In this dry sand, faults form at ~30 degrees to sigma 1. Vertical sigma 1 during extension produces faults dipping 60 degrees, while horizontal sigma 1 during compression produces faults dipping 30 degrees. Normal faults are thus too steep to reactivate, and are overtaken by shallower faults that "shortcut" through pre-rift material. Mechanical contrast or rotation of existing normal faults would be necessary for reactivation.
