Strike and Dip Formats

 

Many geologic features can be approximated as a plane.  Examples include sedimentary bedding, or a fault plane.  Even if the surface actually curves, there will be a plane that is tangent to the surface at every point.

Definitions

  1. Strike.  the orientation of the horizontal line within a plane.  While there are an infinite number of horizontal lines within a plane, they will all be parallel and share the same orientation.  For a horizontal plane, strike is undefined.
  2. Dip direction:  The dip direction will be orthogonal to the strike direction. Water will flow down the plane in this direction.
  3. Apparent dip: if you attempt to measure dip and are not orthogonal to the strike direction, the measured value will be smaller
  4. Dip: steepest angle from the horizontal of a plane.  A horizontal plane has a dip of 0, and a vertical plane a dip of 90.  The larger the dip, the steeper the plane.

 

Image courtesy Eurico Zimbres, Wikipedia.

Dip and strike formats:

  1. Quadrant N34E 69SE, strike, dip, dip direction.  This is the preferred format, at least for traditional field geologists. This takes the end of the line that points northward.  The dip direction has to be only approximately correct, since there are only two possible orientations given the strike.
  2. Right hand rule, 34 69, strike, dip; dip direction in 90 clockwise from strike
  3. Right hand rule with override, 34 69 SE, strike, dip, optional dip direction; right hand rule used if omitted
  4. Dip-dip direction, 69 124 or 69 S56E

Last revision 10/16/2014