Line Structure

Lecture #16

Introduction• The position of line structure can be presented

with plunge and trend.

• If the line structure on plane structure which the position known, then the line structure can be represented by pitch.

Plunge• An angle that form by line structure with horizontal

plane which is measure on the vertical plane.• Has range from 0° to 90 °

Shallow 0° – 20°Moderate 20°- 50°Steep 50° - 90°

Trend• The direction of line structure projection to the

horizontal plane.• Line structure and the projection need to be in the

same vertical plane• Trend able to show the direction of the line structure.• Trend to west and trend to east is totally different.

Pitch• The vertical angle between the horizontal plane and

the axis or line of maximum elongation of a feature

Solve line structure problem with geometry descriptive

• In every line structure, the magnitude of plunge and apparent dip of plane structure is same.

• Example: Determine line structure plunge and pitch of the plane structure. a plane structure has strike and dip N45°E/30°SE, and has line structure with trend N180°E. Determine the plunge and pitch of the line structure?

Solution

1. Imagine, COED, is the slope plane, Height differences between CO strike with DE strike is t. FG line is the projection of DE on the map.

2. Draw strike line on N45°E direction, and draw a perpendicular line on this strike line and label it with CI

3. Assume that CI line is the fold line F1, and rotate the cross section to the map plane. Draw CJ line with an angle 30° relatively to CI

4. Draw perpendicular line to CI and label it with KL, this line will cut the CI and CJ line and label both point with F and D’- KL line is the projection line from DE strike on map- Height differences between CO and DE strike is FD’ (t)

5. Draw line with direction N180°E from point O and label the line with OA, the projection to map.

6. Make OA as the fold line 2, and rotate cross section into map plane. Draw AB’’ line perpendicular to OA as many as t.

7. Draw OB’’ line. ˪AOB’’ is the plunge of line structure.

8. Make CO line as fold line 3, and rotate the COED plane to map plane. Using Compass draw arc that connecting D’ to D’’, where D’’ located along CI line and C as the center of the arc. Length of CD’’ = CD’

C

H

D

O

G

A

B

EF

t

t

N45°E

N180°E

45°

?

9. Draw rectangle COE’D”. This rectangle is slope plane COED which has been rotated to map projection. Point B which is on the slope plane also being rotated on the map plane B’. CO line act as fold line.10. Draw OB’ line, which is the OB structure line that already rotated to map plane. ˪COB is the pitch.

Plunge

N180°E

N45°E

pitch

G

L

E’

O

B’’

B’

At

t D”

D’

J

C

30°

F

I

K C

H

D

O

G

A

B

EF

t

t

N45°E

N180°E

45°

?

Draw line with direction N180°E from point O and label the line with OA, the projection to map.

Draw OB’’ line. ˪AOB’’ is the plunge of line structure.

Draw OB’ line, which is the OB structure line that already rotated to map plane. ˪COB is the pitch.

Draw perpendicular line to CI and label it with KL, this line will cut the CI and CJ line and label both point with F and D’- KL line is the projection line from DE strike on map- Height differences between CO and DE strike is FD’ (t)

Assume that CI line is the fold line F1, and rotate the cross section to the map plane. Draw CJ line with an angle 30° relatively to CI

Draw strike line on N45°E direction, and draw a perpendicular line on this strike line and label it with CI

Make CO line as fold line 3, and rotate the COED plane to map plane. Using Compass draw arc that connecting D’ to D’’, where D’’ located along CI line and C as the center of the arc. Length of CD’’ = CD’

Draw rectangle COE’D”. This rectangle is slope plane COED which has been rotated to map projection. Point B which is on the slope plane also being rotated on the map plane B’. CO line act as fold line.

Make OA as the fold line 2, and rotate cross section into map plane. Draw AB’’ line perpendicular to OA as many as t.

Questi ons…