Geology 360 - Geology 360 - FaultsFaults

OutlineOutline

• Fault components

• Slip verses separation

• Faulting styles

• Piercing points

• Calculating slip from piercing points

• Fault exercises

Kobe Earthquake Fault Rupture Kobe Earthquake Fault Rupture

MuseumMuseum

Fault ComponentsFault Components

• Footwall

• Hanging wall

• Fault plane, fault surface

Footwall

Hanging wall

Slip verses SeparationSlip verses Separation

Pre-faulted block Faulted block Eroded block

• Slip - actual relative displacement between two points that occupied

the same location before faulting

• Separation - apparent relative displacement between two points that

may have occupied the same location before faulting

Slip Separation

Faulting StylesFaulting Styles

Normal

Thrust

Strike-slip

Dip-slip

Dip-slip

Strike-slip

Faulting StylesFaulting Styles

Oblique-slip: a combination of dip-slip and strike-slip

Fault Exercises - ExampleFault Exercises - Example

Pre-faulted block Faulted block Eroded block

?? ??

Fault Exercises - ExampleFault Exercises - Example

Pre-faulted block Faulted block Eroded block

??

Fault Exercises - ExampleFault Exercises - Example

Pre-faulted block Faulted block Eroded block

Fault ExercisesFault Exercises

• Study the examples in ia, ib, ic

• Fill in the beds in the remaining six diagrams keeping in mind the effects faulting and erosion

Example 2Example 2

?? ??

Pre-faulted block Faulted block Eroded block

Example 2Example 2

??

Pre-faulted block Faulted block Eroded block

Example 2Example 2

Pre-faulted block Faulted block Eroded block

Example 3Example 3

Pre-faulted block Faulted block Eroded block

?? ??

Example 3Example 3

Pre-faulted block Faulted block Eroded block

??

Example 3Example 3

Pre-faulted block Faulted block Eroded block

Example 4Example 4

Pre-faulted block Faulted block Eroded block

?? ??

Example 4Example 4

Pre-faulted block Faulted block Eroded block

??

Example 4Example 4

Pre-faulted block Faulted block Eroded block

Piercing Piercing

PointsPoints

Calculating SlipCalculating Slip

AA

BB

Given:Given:

Position coordinates (x,y,z) in metersPosition coordinates (x,y,z) in meters

A (2, 3, 10)A (2, 3, 10)

B (7,11, 3)B (7,11, 3)

Problem:Problem: Determine slipDetermine slip

(trend, plunge, magnitude)(trend, plunge, magnitude)

Calculating SlipCalculating Slip

X

TrendTrend

X = (7-2) = 5 mX = (7-2) = 5 m

Y = (11-3) = 8 mY = (11-3) = 8 m

M = (M = (XX22+ + YY22))0.50.5 = (5 = (522+8+822))0.5 0.5 = 9.4 m= 9.4 m

Magnitude = 9.4 mMagnitude = 9.4 m

Tan Tan = = Y/ Y/ XX

= Tan= Tan-1-1(8/5)(8/5)

= 58°= 58°

Azimuth = 90°-58° = 032°Azimuth = 90°-58° = 032°

Y

A (2, 3, 10)A (2, 3, 10)

B (7,11, 3)B (7,11, 3)

xx

yyNN

00

PlungePlunge

M = 9.4 mM = 9.4 m

Z = (10-3) = 7 mZ = (10-3) = 7 m

S = (S = (22+ + ZZ22))0.50.5 = (9.4 = (9.422+7+722))0.5 0.5 = 11.7 m= 11.7 m

Total slip [S] = 11.7 mTotal slip [S] = 11.7 m

Tan Tan = = Z/ MZ/ M

= Tan= Tan-1-1(7/9.4)(7/9.4)

= 37°= 37°

Plunge value = 37°Plunge value = 37°

SolutionSolution: slip vector 37°,032°; 11.7 m magnitude: slip vector 37°,032°; 11.7 m magnitude

Calculating SlipCalculating Slip

SZ

xx

zzSWSW

00

NENE