Basement-Involved Oblique Faulting

Photo "Map view" of top surface of scaled clay model of basement-involved oblique-slip faulting. The clay was deformed as a fault system propagated upward from a rigid basement block into the clay. Bright features are synthetic fault scarps dipping toward the base of the image; dark features are antithetic fault scarps dipping away from the base of the image. Although the basement fault is one continuous fault, the fault system in the cover consists of several segments arranged in an echelon geometry, with relay ramps between the overlapping synthetic segments. The strike of the fault segments is oblique to the trend of the deformed zone (NW-SE). The basement fault strikes at a 45 degree angle to the movement direction (due S), and dips at a 45 degree angle to the SW.
Vertical slice through clay model similar to the one above. The slice was prepared after the clay had dried and hardened. Faults cutting the uppermost blue clay layer correspond to those shown in the map view above. Both synthetic and antithetic faults cut the extensional forced fold that developed in the clay. The experimental models were run at Mobil Technology Company by Roy W. Schlische, Martha Withjack, and Gloria Eisenstadt.