Stress Regime Assignment 
The stress magnitudes are defined using the standard geologic/geophysical
notation with compressive stress positive and S1>S2>S3, so that S1 is
the maximum and S3 the minimum principal compressive stress.

The following categories are used to describe the tectonic stress regime: 
NF: Normal faulting 

NS: Predominately normal faulting with strikeslip component 

SS: Strikeslip faulting 

TS: Predominately thrust faulting with strikeslip component 

TF: Thrust faulting 

U: Unknown (largely breakout data with no stress magnitude
information available; also see below). 
Besides the standard NF, TF, and SS categories, combinations of NF with SS (NS)
and TF with SS (TS) exist (Zoback, 1992). NS represents data where the maximum
stress or Paxis is the steeper plunging of the P and Baxes. TS represents data
where the minimum stress or Taxis is the steeper plunging of the B and Taxes.
The plunges (pl) of P, B, and Taxes (or S1, S2, and S3 axes) used to assign the
stress data to the appropriate stress regime are given in the table below (according
to Zoback, 1992). 
blind 
P/S1axis 
B/S2axis 
T/S3axis 
Regime 
SHazimuth 
pl > 52 

pl < 35 
NF 
azim. of Baxis 

40 < pl < 52 

pl < 20 
NS 
azim. of Taxis +90 

pl < 40 
pl > 45 
pl < 20 
SS 
azim. of Taxis +90 

pl < 20 
pl > 45 
pl < 40 
SS 
azim. of Paxis 

pl < 20 

40 < pl < 52 
TS 
azim. of Paxis 

pl < 35 

pl > 52 
TF 
azim. of Paxis 
