Apparent dip is any dip measured in a vertical plane not perpendicular to the strike line. True dip can be calculated from apparent dip using trigonometry if you know the strike. Geologic cross sections use apparent dip when they are drawn at some angle not perpendicular to strike.
T true thickness
P2 top of unit P1 bottom of unit D true dip
S apparent thickness T = S * cos (D) |
To resolve true dip and thickness, look at two cross sections as close to 90 degrees apart as possible. This is the reason that seismic surveys like to use tie lines to constrain the true 3D geometry.
Last revision 11/4/2014