Attitudes of planes and lines. Description of folds, faults, and in other structures requires the specification of the attitude (i.e. the orientation in space) of planar and linear elements associated with these structures. The attitude of a planar surface is fully described by three parameters: Its strike, its dip, and its dip direction. The attitude of a line is fully described by its plunge and its plunge direction. Its is most important for you to have a clear definition of all those parameters.
Strike: The strike of a plane is the azimuth of the "strike line" of the plane. The strike line is an horizontal line on the plane under consideration. (The azimuth is measured clockwise along an horizontal plane from the North direction to the strike line).
Dip: The dip of a plane is an angle measured from an horizontal plane down to the plane under consideration. The dip is measured along a vertical plane perpendicular to the strike line of the plane.
Dip Direction: Two planes may have the same strike an dip. What differentiate them is the direction of the dip expressed by the geographic quadrant (N, NNE, NE, ENE, E, ESE, SE, SSE, S, etc...) the planes are facing.
By convention the strike is expressed by a three digit number, and the dip by a two digit number. A plane striking 25º and dipping 45º toward the northwest will be noted: 025-45NW
|Plunge: The plunge of a line is analogous to the dip of a plane. It is measured along the vertical plane that contain the line, from an horizontal plane down to the line.
Plunge direction: Two lines may have the same plunge. What differentiate them is the direction of the plunge expressed by the geographic quadrant (N, NNE, NE, ENE, E, EES, SSE, SE, etc...) the lines are facing.
By convention the plunge direction is expressed by a three-digit number, and the plunge by a two-digit number. A line plunging 35º toward the azimuth 35º will be noted: 45º->035
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