Detached Normal Faults

Photo Scaled physical model of detached normal faults. The model conists of alternating sand layers of different color placed over a viscous layer of putty, which is used to simulate salt or ductile shale. Flowage of the putty to the right was accomplished by removing a wall originally located above the "4" in the time stamp. As the putty flowed to the right, the overlying sand was extended, forming normal faults. The top slide shows a map view of the faults. Bright faults dip to the right; dark faults dip to the left.
The bottom slide shows a vertical slice (cross-section view) through the model produced after the experiment. Note the normal faults that detach into the putty. The lowest four sand layers were laid down before the wall was removed. The other layers were "deposited" during the experiment. These are "growth" layers that thicken toward the normal faults in their hanging-wall blocks. Slides courtesy of Bruno Vendeville of the Applied Geodynamics Lab, Bureau of Economic Geology, University of Texas at Austin