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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.

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Link	Block	Gravity	Magnetics	Magnetics	Magnetics at Pole	Magnetics at Pole 1VD
Fault dipping 40° to South, down slip vector, normal fault	LOAD JPEG IMAGE	LOAD JPEG IMAGE	LOAD JPEG IMAGE	LOAD JPEG IMAGE	LOAD JPEG IMAGE	LOAD JPEG IMAGE
	Notice the uniform apparent senses of movement of the two dykes.
Fault dipping 40° to North, down slip vector, normal fault	LOAD JPEG IMAGE	LOAD JPEG IMAGE	LOAD JPEG IMAGE	LOAD JPEG IMAGE	LOAD JPEG IMAGE	LOAD JPEG IMAGE
	Notice the apparent opposite senses of movement of the two dykes.
Faults dipping 40° to South, horizontal slip vector, sinistral fault	LOAD JPEG IMAGE	LOAD JPEG IMAGE	LOAD JPEG IMAGE	LOAD JPEG IMAGE	LOAD JPEG IMAGE	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	LOAD JPEG IMAGE	LOAD JPEG IMAGE	LOAD JPEG IMAGE	LOAD JPEG IMAGE	LOAD JPEG IMAGE	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	LOAD JPEG IMAGE	LOAD JPEG IMAGE	LOAD JPEG IMAGE	LOAD JPEG IMAGE	LOAD JPEG IMAGE	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	LOAD JPEG IMAGE	LOAD JPEG IMAGE	LOAD JPEG IMAGE	LOAD JPEG IMAGE	LOAD JPEG IMAGE	LOAD JPEG IMAGE

Key	Earth's Magnetic Field	Scales
Dyke r = 1 k = 10-2 Background r = 0 k = 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

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Copyright © 1998-2002 AGCRC & Mark Jessell

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