To correctly recognize a fault, you must first figure the end which block is the footwall and which is the hanging wall. Then you identify the family member motion in between the hanging wall and footwall. Every error tilted native the vertical has actually a hanging wall surface and footwall. To recognize which is which, visualize yourself producing a mine in follow me the error plane. The block listed below your feet is the footwall, and the one upon which you would certainly hang your miner"s lamp is the hanging wall. That is that simple. Strike-slip faults room vertical and thus do not have hanging walls or footwalls. If the hanging wall drops relative to the footwall, you have actually a typical fault. Common faults take place in locations undergoing expansion (stretching). If you imagine undoing the motion of a typical fault, you will undo the stretching and thus shorten the horizontal distance between two points on either next of the fault.
|If friend stood top top the error plane, the block on the appropriate would it is in under your feet. This is thus the footwall.The red line marks equivalent layers ~ above opposite side of the fault. Due to the fact that the hanging wall dropped family member to the footwall, this is plainly a normal fault.|
Photo: special limestone bed in northerm Mexico, through Norris W. Jones
|The striking black layer is a welded tuff (volcanic ash the remelted itself to end up being solid glassy rock). There are three common faults in the pink tuffs to the ideal of the welded tuff. At the feet the the human is the very same orange layer as the faulted one seen just over the roadway in the middle of the photo. A 2nd fault cut the orange class in the center of the photo. A 3rd one operation from the left end of this faulted layer down to the person.|
|Normal faults often occur in pairs, with one being the main fault and also the other being a smaller conjuagate fault.The red lines present the balance out on the right-hand fault. Given the angle of the fault, the upper red heat is ~ above the footwall, the lower red heat is top top the hanging wall.|
Bishop Tuff lake sediments, Owen Valley, CA.
|This hill of nicely layers limestones shows several set of typical faults offsetting the influential white band close to the peak of the mountain. If you focus on each fault, the counter of each hanging wall from each foot wall surface indicates common fault motion.Near the race Track, death Valley, CA|
|Many normal faults have so lot offset that you cannot map individual beds across a single outcrop. However, sometimes the beds have actually been bent by the dragging that the hanging wall surface over the footwall.|
See more: Why Are Halogens Ortho Para Directors But Deactivating Group
In this case, the beds on the appropriate of this fault have been bent downwards by common fault motion.
Mosaic Canyon, fatality Valley, CA
Return to GeoImage home Page
|E-mail C.E.Jones with comments or corrections||Geology and Planetary science HomePage|