structural geology (fault)(2)

                                                                   FAULT

It is a plane of weakness developed in rock bodies due to tensional forces along which relative movement of the beds or lava flow takes place is called fault.

·        Fractures are passive consequence of the tectonic forces without any movement of beds or lava flows is called Fracture.

·        Parts of Fault

1.     The plane along which movement has taken place is called Fault plane

2.     Strike of Fault – It is direction of line form by the intersection of fault plane with horizontal

3.     Dip of Fault – It is angle made by fault plane with Horizontal

4.     Hade of Fault – It is angle made by fault plane with vertical

5.     Throw of Fault – The vertical displacement of beds is called throw of the fault

6.     Heave of Fault – It is Horizontal displacement of beds is called Heave of fault

7.     Up throw side – side which is thrown upward

8.     Down throw side- side which is thrown downward

9.     Hanging wall – The block above the                                                                            Foot wall – The block below the fault plane.

ABCD = fault plane

FW = foot wall

HW = Hanging wall

AC = fault plane

D = Dip of fault

AO = Throw of fault

OC = Heave of fault

Q = Hade of fault

Types of faults

A)  Based on Attitude of fault plane

a   Vertical fault – if fault plane is vertical

bInclined fault – if fault plane is oblique

     Strike fault – if fault plane is parallel to strike of beds

d    Dip fault – if fault plane is parallel to dip of beds

B)    

C)   Based on Angle Fault Plane

a    High angle fault

    Low angle fault

D)  Based on apparent movement

a   Normal Fault

It is inclined fault

Fault plane is steep

Due to tensional forces.

HW has gone as compared F.W.

Dip a fault plane is in the same

 direction as down throw side

  Reverse Fault

It is Inclined fault

Fault plane is gently dipping

Due to strong lateral compressive forces

HW has gone up as compared to F.W.

Dip of fault plane is an opposite

direction that of the down throw of fault

E)   Based on Gravity

a    Horst or Ridge fault

·        Two parallel fault

·        Central block thrown up

·        Topographic elevation (Ridge)

b)  Graben or Trough fault (Rift valley)

·        Central block goes down

·        Topographic depression

·        Formation of Rift valley

       

Based on fault pattern

a)     Parallel fault – A series of fault having same dip & strike

b)    Step fault – step like appearance

c)     Radial fault – Radiating Pattern

d)    Peripheral fault – curved fault

e)     Over thrust fault – due to strong lateral compressive forces acting on one direction