Geophysicks

Three component VSP (Vertical Seismic Profiling) consist of X component , Y component and Z component. The three component are rotated to obtain pure direct, perpendicular, and transverse component.

Normal stress
The component perpendicular to the wavefront plane is termed normal stress.
The receiver recieves this signal as direct component which is compresional wave.

Shear stress
The component parallel to the wavefront plane is termed shear stress.
The receiver recieves this signal as perpendicular component which is shear wave.

To obtain the direct wave and shear wave, rotation is done twice.

Horizontal Rotation
Horizontal components are rotated thus one component receives maximum response while the other one receives the minimum one.

Vertical Rotation
Vertical rotation is done thus one component recieves maximum response while the other one receives the minimum one.

Following is flash illustration to help understand the VSP component better

or you can view it bigger here