1. Fault Classification
Bases of fault classification: Faults can be classified on the basis of their geometry and genesis. Geometric classification is easy to apply than genetic classification.
A. Geometrical classification:
1. the rake of the net slip. 2. the attitude of the fault relative to the attitude of the adjacent rocks. 3. the pattern of the faults. 4. the angle at which the fault dips. 5. the apparent movement on the fault.
B. Genetic classification:
1. classification based on relative movements. 2. classification based on absolute movements.

2. Fault Classification A. Geometrical classification:
1. the rake of the net slip. 2. the attitude of the fault relative to the attitude of the adjacent rocks. 3. the pattern of the faults. 4. the angle at which the fault dips. 5. the apparent movement on the fault.

3. Fault Classification A. Geometrical classification:
1. Classification based on the rake of the net slip.
a. STRIKE SLIP FAULT: is one in which the net slip is parallel to the strike of the fault.
b. DIP SLIP FAULT: is one in which the net slip is up or down the dip of the fault; that is the dip slip equals the net slip and there is no strike slip component. The rake of the net slip is therefore 90 degrees.
c. DIAGONAL SLIP FAULT: is one in which the net slip is diagonally up or down the fault plane. There is both a strike slip and dip slip component, the rake of the net slip is greater than zero but less than 90 degrees.

4. Fault Classification A. Geometrical classification:
2. Classification based on the attitude of fault relative to the strike of the adjacent rocks.
a. Strike Fault
b. Bedding Fault
c. Dip Fault
d. Oblique / Diagonal Fault
e. Longitudinal Fault
f. Transverse Fault

5. Fault Classification A. Geometrical classification:
2. Classification based on the attitude of fault relative to the strike of the adjacent rocks.
a. STRIKE FAULT: is one that strikes essentially parallel to the strike of the adjacent rocks. The strike of the adjacent rocks is ordinarily measured on the bedding, but if the bedding is absent, the strike may be measured on the schistosity of metamorphic rocks or on the flow structure of igneous rocks.

6. Fault Classification A. Geometrical classification:
2. Classification based on the attitude of fault relative to the strike of the adjacent rocks.
b. BEDDING FAULT: is a variety of strike fault in which the fault plane is essentially parallel to the bedding.

7. Fault Classification A. Geometrical classification:
2. Classification based on the attitude of fault relative to the strike of the adjacent rocks.
c. DIP FAULT: is one that strikes essentially parallel to the direction of dip of the adjacent beds; that is, its strike is perpendicular to the strike of the adjacent beds.

8. Fault Classification A. Geometrical classification:
2. Classification based on the attitude of fault relative to the strike of the adjacent rocks.
d. OBLIQUE or DIAGONAL FAULT: is one that strikes obliquely or diagonally to the strike of the adjacent rocks.

9. Fault Classification A. Geometrical classification:
2. Classification based on the attitude of fault relative to the strike of the adjacent rocks.
e. LONGITUDINAL FAULT: is one that strikes parallel to the strike of the regional structure.
f. TRANSVERSE FAULT: is one that strikes perpendicularly or diagonally to the strike of the regional structure.

10. Fault Classification A. Geometrical classification:
3. Classification based on the pattern of the faults.
A third geometrical classification is based on the pattern shown by the faults; ordinarily the classification is based on the pattern on a map, but it may be based on the pattern in a cross section. The attitude of the adjacent rocks is unimportant.
a. Parallel faults
b. En-echelon faults
c. Peripheral faults
d. Radial faults.

11. Fault Classification A. Geometrical classification:
3. Classification based on the pattern of the faults.
A third geometrical classification is based on the pattern shown by the faults; ordinarily the classification is based on the pattern on a map, but it may be based on the pattern in a cross section. The attitude of the adjacent rocks is unimportant.
a. Parallel faults
b. En-echelon faults
c. Peripheral faults
d. Radial faults.
a. Parallel faults: Parallel faults have essentially the same dip and strike; they thus belong to a set of parallel faults. If the strikes are the same but the dips differ the faults are assigned to two or more sets of parallel faults.

12. Fault Classification A. Geometrical classification:
3. Classification based on the pattern of the faults.
A third geometrical classification is based on the pattern shown by the faults; ordinarily the classification is based on the pattern on a map, but it may be based on the pattern in a cross section. The attitude of the adjacent rocks is unimportant.
a. Parallel faults
b. En-echelon faults
c. Peripheral faults
d. Radial faults.
b. En-echelon faults: are relatively short faults that overlap each other.

13. Fault Classification A. Geometrical classification:
3. Classification based on the pattern of the faults.
A third geometrical classification is based on the pattern shown by the faults; ordinarily the classification is based on the pattern on a map, but it may be based on the pattern in a cross section. The attitude of the adjacent rocks is unimportant.
a. Parallel faults
b. En-echelon faults
c. Peripheral faults
d. Radial faults.
c. Peripheral faults: are circular or arcuate faults that bound a circular area or part of a circular area.

14. Fault Classification A. Geometrical classification:
3. Classification based on the pattern of the faults.
A third geometrical classification is based on the pattern shown by the faults; ordinarily the classification is based on the pattern on a map, but it may be based on the pattern in a cross section. The attitude of the adjacent rocks is unimportant.
a. Parallel faults
b. En-echelon faults
c. Peripheral faults
d. Radial faults.
d. Radial faults: Radial faults belong to a system of faults that radiate out from a point.

15. Fault Classification A. Geometrical classification:
4. Classification based on value of dip of fault.
a. High-angle faults
b. Low-angle faults

16. Fault Classification A. Geometrical classification:
4. Classification based on value of dip of fault.
a. High-angle faults
b. Low-angle faults
a. High-angle faults: are those that fault plane dip greater than 45 degrees.
b. Low-angle faults: are those that fault plane dip less than 45 degrees.

17. Fault Classification A. Geometrical classification:
5. Classification based on apparent movement.
A fifth geometrical classification is based upon the apparent movement in vertical sections at right angles to the fault.
a. Apparent normal fault
b. Apparent thrust fault

18. Fault Classification A. Geometrical classification:
5. Classification based on apparent movement.
A fifth geometrical classification is based upon the apparent movement in vertical sections at right angles to the fault.
a. Apparent normal fault
An apparent normal fault is one in which the hanging wall, in a vertical section at right angles to the strike of the fault, appears to have gone down relative to the footwall.

19. Fault Classification A. Geometrical classification:
5. Classification based on apparent movement.
A fifth geometrical classification is based upon the apparent movement in vertical sections at right angles to the fault.
b. Apparent thrust fault
An apparent thrust fault is one in which the hanging wall, in a vertical section at right angles to the strike of the fault, appears to have gone up relative to the footwall.

20. Fault Classification B. Genetic classification:
The ideal and most satisfactory classification in natural sciences are those based on genesis. An ideal genetic classification of faults would be based primarily on the nature of forces involved. Such a classification should considered not only whether the forces were compressional, tensional, shearing or torsional; but it should considere also the direction in which those forces were acting.
1. Classification based on relative movements.
2. Classification based on absolute movements.

21. Fault Classification B. Genetic classification:
1. Classification based on relative movements.
The most satisfactory genetic classification that can be established at present is based on the nature of relative movement along the fault.
a. Thrust fault
b. Normal fault
c. Strike slip fault

22. Fault Classification B. Genetic classification: a. Thrust fault
THRUST FAULT or thrust is a fault along which the hanging wall has moved up relative to the footwall. Three categories are usually recognized:
A reverse fault is a thrust that dips more than 45 degrees, the term thrust is one that dips less than 45 degrees, but overthrust is used for a fault that dips less than about 10 degrees and has a large net slip. Overthrust has also been used with different connotation. Thrust faults indicate shortening of the rocks involved.
Reverse fault
Thrust fault
Overthrust fault

23. Normal fault or Gravity fault
Fault Classification
B. Genetic classification:
b. Normal fault
NORMAL FAULT is a fault along which the hanging wall has moved relatively downward. It is also called gravity fault, but not generally followed by geologists.
Detachment fault
Normal fault or Gravity fault
A detachment fault is a special category of low angle normal fault due to the downhill sliding of rocks from an uplifted region.

24. Fault Classification B. Genetic classification: c. Strike slip fault
STRIKE SLIP FAULTS also called wrench faults, are those along which displacement has been essentially parallel to the strike of the fault --- that is, the dip slip component is small compared to the strike slip component.
If an observer approaches a strike slip fault from one side, the opposite wall will have moved relatively either to the right or left.
A right-slip fault is one in which the opposite wall moved relatively to the right. The terms dextral, right-handed and right-lateral have been used.
A left-slip fault is one in which the opposite wall moved relatively to the left. Similarly, the terms sinistral, left-handed and left-lateral have been used.

25. Fault Classification B. Genetic classification:
2. Classification based on absolute movements.
A more elaborate classification would be based on absolute movements relative to some datum plane, such as sea level.
a. Normal faults
b. Thrust faults
c. Upthrust
d. Underthrust
d. Overthrust

26. Fault Classification B. Genetic classification: a. Normal faults
Based on absolute movements five kinds of normal faults might be recognized:
i) those in which the foot wall did not move, but in which the hanging wall moved down;
ii) those in which the foot wall moved up, while the hanging wall remained stationary;
iii) those in which the hanging wall moved down and the footwall moved up;
iv) those in which both blocks moved down, but in which the hanging wall moved a greater amount; and
v) those in which both blocks moved up, but in which the hanging wall moved less than footwall.

27. Fault Classification B. Genetic classification: b. Reverse faults
Similarly, five kinds of thrust / reverse faults might be established. These are illustrated in the following figures:

28. active block Fault Classification B. Genetic classification:
c. Upthrust
UPTHRUSTS are high-angle faults along which the relatively uplifted block has been the active element. If the hanging wall of a high-angle thrust fault has moved up while the footwall stayed in place, or the footwall of a high-angle normal fault has moved up while the hanging wall stayed in place, the fault is an upthrust.
Stationary block
Stationary block
active block

29. Fault Classification B. Genetic classification: d. Underthrust
UNDERTHRUST is used for those thrust faults in which the footwall has been the active element.
Stationary
Block
Active
Block

30. Fault Classification B. Genetic classification: e. Overthrust
OVERTHRUST is used for those thrust faults in which the hanging wall has been the active element.
Active Block
Stationary Block