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Normal or Reverse?

This article explores the different types of vertical displacement in dip-slip faults using the hanging wall method. Learn how to identify the hanging wall and footwall and determine if the fault is normal or reverse.

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Normal or Reverse?

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  1. Normal or Reverse? Looking at the two types of vertical displacement in dip-slip faults using the hanging wall method

  2. Terminology An easy method to decide what sort of dip-slip fault we have uses the old mining terms of: Hanging wall and Footwall

  3. The hanging wall is always on top of the fault fault Hanging wall Footwall The footwall is always underneath the fault These names do not need us to know which side has moved up or down or if a tension or compression has occurred fault

  4. 1 km We apply this to the fault we looked at in the introduction to faults. Hanging wall Hanging Wall Footwall The block above the fault plane is the hanging wall, and the block below the fault is the footwall. Footwall fault

  5. Draw arrows to show the relative movement on either side of the fault. Hanging wall ⇃ ↾ Footwall

  6. Is the footwall the upthrow side or downthrow side of the fault? Hanging wall ⇃ ↾ Upthrow The arrow points up, it must be the upthrow side. F Footwall Upthrow U Normal N Footwall U N ! F This makes This is a normal fault.

  7. Normal faults are caused by a pulling apart motion (tension). Hanging wall ⇃ ↾ Upthrow Footwall

  8. Another example

  9. 1 km Two interpreted horizons. Hanging wall Two faults. Look at the fault in the NW. The block above the fault plane is the hanging wall, and the block below the fault is the footwall. Footwall

  10. 1 km Draw arrows to show the relative movement on either side of the fault. Hanging wall ⇃ ↾ Footwall

  11. 1 km Is the footwall the upthrow side or downthrow side of the fault? Hanging wall ⇃ The arrow points down, it must be the downthrow side. ↾ Footwall Downthrow This does not make FUN! Footwall This is a reverse fault.

  12. 1 km Reverse faults are caused by a pushing together motion (compression). Hanging wall ⇃ ↾ Footwall

  13. 1 km Try the other fault. Hanging wall The block above the fault plane is the hanging wall, and the block below the fault is the footwall. Footwall

  14. 1 km Draw arrows to show the relative movement on either side of the fault. Hanging wall Footwall ↿ ⇂

  15. 1 km Is the footwall the upthrow side or downthrow side of the fault? Hanging wall Footwall ↿ The arrow points down, it must be the downthrow side. ⇂ Footwall Downthrow This does not make FUN! This is a reverse fault.

  16. 1 km Reverse faults are caused by a pushing together motion (compression). Hanging wall Footwall ↿ ⇂

  17. 1 km There are many more faults on this seismic profile. ↿ ↿ ↿ ⇃ ↿ ↿ ↿ ⇃ ⇂ ↾ ⇂ ↾ ⇂ ⇂ ⇂ ⇂ Click to see a few suggestions. Do you agree?

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