Structural Geology and Tectonics: Faults Chapter 1 (ERS 253 CIIT)

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Questions and Answers

What is the net slip of a fault?

The distance between two parts of a disrupted horizon

The angle between the fault plane and the horizontal

The movement of the Earth's crust along the fault plane

The magnitude and direction of relative displacement on the fault plane (correct)

When is the component of strike slip zero?

When the net slip is parallel to the strike

When the net slip is perpendicular to the fault plane

When the net slip is parallel to the dip (correct)

When the net slip is oblique to the fault plane

What is the term for the vertical component of dip separation?

Heave

Offset

Vertical separation

Throw (correct)

What is the direction of measurement for horizontal separation?

Along a horizontal line Signup and view all the answers

What type of slip occurs when the net slip is oblique to the dip direction of the fault?

Oblique slip Signup and view all the answers

What is the term for the distance measured perpendicular to the disrupted horizon?

Offset or normal separation Signup and view all the answers

What is the direction of the σ2 axis in relation to the fault plane?

Perpendicular to the fault plane Signup and view all the answers

What is the purpose of constructing the M-plane in structural geology?

To determine the orientation of the slip lineation Signup and view all the answers

What is the term for the angle between the slip lineation and the horizontal?

Rake Signup and view all the answers

What type of indicators on the fault surface can provide the sense of slip?

Shear indicators Signup and view all the answers

What is the orientation of the slip lineation in relation to the fault plane?

Parallel to the fault plane Signup and view all the answers

What is the term for the description of the fault's orientation in terms of strike and dip?

Attitude of the fault Signup and view all the answers

What is the basis of geometric classification of faults?

Slip direction, dip angle, and fault pattern Signup and view all the answers

What type of faults occur when the slip is parallel to the dip direction?

Dip-slip faults Signup and view all the answers

What is the characteristic of low-angle faults?

Dip angle is less than 45 degrees Signup and view all the answers

What type of faults are characterized by an overlapping pattern?

En-echelon faults Signup and view all the answers

What is the purpose of genetic classification of faults?

To specify the dynamic terms with consideration of stress orientation during fault development Signup and view all the answers

What is the significance of principal stress being vertical in genetic classification?

It indicates zero shear stress at the earth's surface Signup and view all the answers

What is the definition of a fault in structural geology?

A fracture across which relative displacement of opposite sides is observed with respect to each other Signup and view all the answers

What is the term for the point where the displacement along a fault dies out to zero?

Tip Point Signup and view all the answers

What is the term for the line connecting all the tip points of a fault?

Tip Line Signup and view all the answers

What is the term for the line of intersection of a fault with the ground surface?

Fault Trace Signup and view all the answers

What is the type of fault that does not reach the ground surface?

Blind Fault Signup and view all the answers

What is the term for the displacement between formerly adjacent points on opposite sides of a fault?

Slip Signup and view all the answers

What type of failure occurs along sharply defined faults at shallow depths?

Brittle failure Signup and view all the answers

What is characteristic of ductile behavior in rocks?

Strain is distributed without formation of mesoscopic discontinuities Signup and view all the answers

What is the typical depth range for ductile shear zones?

10 - 15 km Signup and view all the answers

What is the result of brittle behavior in rocks?

Loss of continuity and cohesion Signup and view all the answers

What is the difference between brittle and ductile shear zones?

Brittle shear zones have sharply defined faults, while ductile shear zones do not Signup and view all the answers

What type of deformation mechanisms can occur in ductile behavior?

Both brittle and plastic deformation Signup and view all the answers

Study Notes

Fault Concepts and Definitions

Net Slip: Refers to the magnitude and direction of relative displacement between two adjacent points on a fault plane; described as a vector requiring both magnitude and direction.
Slip Types:
- Dip Slip: Net slip is parallel to the fault dip, with no strike-slip component.
- Strike Slip: Net slip is parallel to the fault strike, with no dip-slip component.
- Oblique Slip: Net slip is at an angle to both strike and dip, containing both strike-slips and dip-slips.

Separation and Fault Measurements

Separation: Distance between disrupted horizon parts, measured in any direction:
- Vertical Separation: Measured along a vertical line.
- Horizontal Separation: Measured along a horizontal line.
- Normal Separation: Measured perpendicular to the disrupted horizon.
Throw and Heave:
- Throw: Vertical component of dip separation.
- Heave: Horizontal component of dip separation, both measured on a vertical section perpendicular to the fault's strike.

Fault Plane and Slip Lineations

Slip Lineation: Forms parallel to the net slip on the fault plane, indicating the attitude of the most recent slip with trend and plunge.
Slickensides: Surface features created by the movement along fault planes, aiding in identifying the sense of slip.

Fault Classification

Geometric Classification:
- Based on slip types: dip-slip, strike-slip, oblique-slip (left-lateral or right-lateral).
- Based on dip angle:
 - Low-angle (< 45 degrees)
 - High-angle (> 45 degrees)
- Based on fault patterns: parallel, en-echelon, peripheral, and radial.

Genetic Classification

Focuses on dynamic terms and stress orientations during fault development, requiring one principal stress to be vertical.

General Fault Characteristics

Fault definition involves fractures with observable relative displacement between opposite sides.
Faults can exhibit various geometries, including planar, listric, or staircase forms.
Key Terms:
- Hanging Wall Block: Block situated above the fault.
- Footwall Block: Block situated below the fault.
- Tip Point: Point of zero displacement along a fault, with a line connecting all tip points termed as Tip Line.
- Fault Trace: Intersection of the fault with the ground surface.

Movement Along Faults

Slip: Represents the displacement between adjacent points across faults, can occur under brittle or ductile conditions.
Shear Zones:
- Ranges from brittle to ductile behaviors, with brittle failure characterized by sharp-defined faults and ductile exhibiting more fluid-like behavior.

Behavior of Materials Under Stress

Brittle Behavior: Occurs when rock loses cohesion at shallow depths due to high stress.
Ductile Behavior: Involves rock flow without discontinuities, strain distributed evenly and occurs under high pressures deeper in the earth.

Fault Rock Classification

Foliated vs. non-foliated types characterized by texture and formation processes, typically analyzed in the context of their deformation history.

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Description

Test your understanding of faults in structural geology and tectonics, including their definition, types, and geometric characteristics. This quiz covers the basics of faults, including their attitude, descriptive terms, and more.