contact Cover

 


2.2.5 Interpretating fault offsets


These images demonstrate the difficulties in determining true offsets (or even projected offsets), simply based on outcrop patterns. A model with 2 dipping dykes is faulted by an East-West striking translational fault with the same magnitude of slip, but variations in dip, dip direction, and the direction of slip movement.

All block diagrams are viewed from SW.

Click on the images to launch Noddy. A legend is provided at the end of this page.

Link
Block
Gravity
Magnetics
Magnetics
Magnetics at Pole
Magnetics at Pole 1VD
Fault dipping 40° to South, down slip vector, normal fault

Open history with Noddy Open Geology VRML
View geology model

LOAD JPEG IMAGE

Open gravity with Noddy

LOAD JPEG IMAGE

Open magnetics with Noddy

LOAD JPEG IMAGE

Open magnetics with Noddy

LOAD JPEG IMAGE

Open magnetics at pole with Noddy

LOAD JPEG IMAGE

Open magnetics at pole 1VD with Noddy

LOAD JPEG IMAGE

Notice the uniform apparent senses of movement of the two dykes.
Fault dipping 40° to North, down slip vector, normal fault

Open history with Noddy Open Geology VRML
View geology model

LOAD JPEG IMAGE

Open gravity with Noddy

LOAD JPEG IMAGE

Open magnetics with Noddy

LOAD JPEG IMAGE

Open magnetics with Noddy

LOAD JPEG IMAGE

Open magnetics at pole with Noddy

LOAD JPEG IMAGE

Open magnetics at pole 1VD with Noddy

LOAD JPEG IMAGE

Notice the apparent opposite senses of movement of the two dykes.
Faults dipping 40° to South, horizontal slip vector, sinistral fault

Open history with Noddy Open Geology VRML
View geology model

LOAD JPEG IMAGE

Open gravity with Noddy

LOAD JPEG IMAGE

Open magnetics with Noddy

LOAD JPEG IMAGE

Open magnetics with Noddy

LOAD JPEG IMAGE

Open magnetics at pole with Noddy

LOAD JPEG IMAGE

Open magnetics at pole 1VD with Noddy

LOAD JPEG IMAGE

Notice the uniform apparent senses of movement of the two dykes, and that the movement appears to be sinistral on the top surface, and dextral on the front surface of the block.
Fault dipping 80° to South, down slip vector, normal fault

Open history with Noddy Open Geology VRML
View geology model

LOAD JPEG IMAGE

Open gravity with Noddy

LOAD JPEG IMAGE

Open magnetics with Noddy

LOAD JPEG IMAGE

Open magnetics with Noddy

LOAD JPEG IMAGE

Open magnetics at pole with Noddy

LOAD JPEG IMAGE

Open magnetics at pole 1VD with Noddy

LOAD JPEG IMAGE

Notice the apparent opposite senses of movement of the two dykes.
Faults dipping 40° to South, slip vector 10° off down dip to East

Open history with Noddy Open Geology VRML
View geology model

LOAD JPEG IMAGE

Open gravity with Noddy

LOAD JPEG IMAGE

Open magnetics with Noddy

LOAD JPEG IMAGE

Open magnetics with Noddy

LOAD JPEG IMAGE

Open magnetics at pole with Noddy

LOAD JPEG IMAGE

Open magnetics at pole 1VD with Noddy

LOAD JPEG IMAGE

Notice the uniform apparent senses of movement of the two dykes. In this model the actual projected slip vector is sinistral, but the apparent offsets on the top surface are dextral.
Shear zone dipping 40° to South, down slip vector, normal fault

Open history with Noddy Open Geology VRML
View geology model

LOAD JPEG IMAGE

Open gravity with Noddy

LOAD JPEG IMAGE

Open magnetics with Noddy

LOAD JPEG IMAGE

Open magnetics with Noddy

LOAD JPEG IMAGE

Open magnetics at pole with Noddy

LOAD JPEG IMAGE

Open magnetics at pole 1VD with Noddy

LOAD JPEG IMAGE


Key
Earth's Magnetic Field
Scales
Dyke
r = 1k = 10-2
Background
r = 0k = 1
Image width
10,000 m
Inclination
50° or 90°
Intensity
50,000 or 70,000 gamma
Flying height
80 m

max



min

max



min

All models created using
Noddy
Copyright © 1998-2002 AGCRC & Mark Jessell

WWW conversion by Ian Brayshaw