Visualizing Stress contains a calculator that resolves the normal and shear stress on a plane whose normal makes an angle of q degrees from the maximum principal stress (s1). The fault angle is 90-q. To use the Stress Calculator select Calculators from the menu and then choose Stress from the cascading menu items.
In the text field next to s1 enter the magnitude of the maximum principal stress. Make sure that both values are in equivalent units, e.g., both are entered as bars or kilobars or Pascals. In the text field labeled s3 enter the magnitude of the minimum principal stress. Enter the angle separating a given fault plane and the maximum principal stress in the text field labeled Fault Angle. Click Calculate for the corresponding values of normal stress (sn), shear stress (t), and theta (q).