FAULT-STRIATION PAIR ANALYSIS (F-SPA) Tool

FAULT-STRIATION PAIR ANALYSIS (F-SPA) is an easy-to-use tool for the processing and graphics of geological data to perform kinematic analyzes of Fault-Striation Pair (FSP) from geological field data and focal mechanisms.

We developed an algorithm in MATLAB environment (www.mathworks.com) to make several calculations from fault planes and striation in terms of sense of motion, kinematic classification, and associated deformation pattern. In particular, this tool is useful:

1. to calculate slip rake values (Aki & Richards, 1980) starting from FSP attitude;
2. to calculate trend and plunge of the stria from fault-rake data input;
3. to calculate the angular misfit of a striation not perfectly lying on the fault plane and to modify the striation attitude (trend and plunge) to project it on the fault plane perfectly.
4. to convert slip rake in pitch value;
5. to calculate the conjugate fault and slip vector orientation,
6. to calculate the P-T-B deformation axes with a fixed rupture angle θ of 45 degrees and a variable angle θ (chosen by users);
7. to makes plots of the above information in stereographic projections (Schmidt net).

Three MATLAB scripts are provided: the .m file "strain_calc_from_striae.m" and the .m file "strain_calc_from_rake" to process the input geological datasets and return a text file (.txt) containing all calculated values, and a third .m file " Plot_stereonet” which processes the stereographic projection starting from the previous two.

Input data (in a .txt file) must contain information on the attitude of the FSP in the first case, or information on the attitude of the fault with the relative slip rake value. The specific text formats are described and illustrated in the next sections of this guide.

This code aims to have the greatest number of information obtainable from geological data using a single tool and to implement structural analysis in the field of geology and seismology.