Post on 30-Dec-2015
description
Outcrop on Mars
Strike
• Strike line = a line in a horizontal plane
• Strike = angle between true north and the strike line
• Azimuth = Bearing = angle clockwise from north
Line Orientation
Plunge = angle line makes with horizontal (angle measured in vertical plane)
Bearing = The azimuth of the projection of the line onto the horizontal plane
Special Lines in Dipping Plane
• Strike of plane=bearing of plane’s strike line
• Dip of plane = steepest plunging line in plane
• Ambiguity of dip direction.
• Necessary to define direction, e.g., 45° NE
Strike and Dip Symbols
Rake or Pitch
• Rake or Pitch = angle line makes with the strike line as measured on the plane
True North and Magnetic North
• True North = direction to North Pole
• Magnetic North = direction to Magnetic Pole
• Declination = angular difference between North Pole and magnetic North
True Dip and Apparent Dip
• Dip is always between 0 and 90°
• True dip is measured in vertical plane that is perpendicular to strike line
• Apparent dip is measured in vertical plane that is at arbitrary angle to strike line
• Apparent dip is always less than True Dip
Relationship between True Dip and Apparent Dip
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δa = arctan tan δ t( )cos θ( )[ ]
€
δa = arctan tan δ t( )sin α( )( )or
Where
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δa = apparent dip
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δt = true dip
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α = angle between line of section and strike line