Javier Guerrero | Ph.D. Student at The Univeity of Texas at Austin | LinkedIn
Nicolas Espinoza | Associate Professor at The University of Texas at Austin | LinkedIn

As indicated by its name, an Andersonian cube also known as Andy cube is a cube that illustrares the relationships between faults/fractures and stresses.

This cube is based on the Andersonian Fault Theory developed by Ernest Masson Anderson in 1951 [1] . This theory classifies faults based on the orientation of the stresses (SV, SHmax, & Shmin) and magnitude of the principal stresses (S1, S2, & S3).[2]

More information about fault classification is available in the Introduction to Energy Geomechanics class notes written by Dr. Espinoza.

[Extracted form Introduction to Energy Geomechanics section 2.3.4] [3]

The variations of horizontal stress in the lithosphere give rise to three types of stress regimes, depending on the relative magnitude of horizontal stress with respect to vertical stress (Table 1). Stress is a tensor. Every stress tensor has three characteristic values called principal stresses $S_1$, $S_2$, and $S_3$. The principal stress $S_1$ is the maximum normal stress value in a given direction (maximum total principal stress). The principal stress $S_3$ is the minimum normal stress value in a given direction (minimum total principal stress). The principal stress $S_2$ is an intermediate stress value at a direction perpendicular to $S_1$ and $S_3$.

Table 1. Stress Regimes in the subsurface according to the Andersonian classification

This repository contains an .stl file to 3D print our interpretation of the Andersonian cube. This cube is a great teaching aid to illustrate the relationships between faults and stresses.

Additionally, here is the link to my tinkerCAD profile where you can duplicate the project and make modifications. TinkerCAD.

1. Anderson, E. M. The Dynamics of Faulting and Dyke Formation with Applications to Britain. [2d ed., rev.]. Edinburgh: Oliver and Boyd, 1951. Print.
2. Turko, M. (2022). What is an "Andy Cube?". https://turkotectonics.com/about-andy-cubes-1.
3. Espinoza, N. (2021, February 10). Introduction to Energy Geomechanics. https://dnicolasespinoza.github.io