TruDisp 2.0: software for determining the true displacement of faults

Abstract

Faults are very common in the upper crust of the Earth. They are characterized by a fracture plane along which observable displacement has occurred. The faults cut and displace geological structures such as layers, veins, fold axes, or dikes. For this reason, knowing the true or net displacement is one of the most important things in faulting deformation analysis. Net displacement is calculated by restoring to their original position points that were adjacent before the deformation, these points are called "piercing points". Unfortunately, it is uncommon to know the position of these points in the field, a situation that prevents the true displacement from being directly determined. It is most common to observe markers that have been displaced by the fault, these markers are linear or tabular objects. The displacement observed in the markers is called "separation". Although it is possible to determine the true displacement using separations, it is not common calculating it during routine geological work. That is because possible configurations of the parameters involved are numerous, and the graphical or trigonometric methods are slow and tedious. In response to this problem, our group developed an application called TruDisp, which calculates the true displacement of a fault from separations. The program calculates the magnitude of displacement, without considering the fault kind (reverse, normal oblique). In this contribution, we present the 2.0 version of that program, which presents significant changes to the previous one. TruDisp 2.0 runs in web browsers displaying a completely new GUI (Graphical User Interface). The input data is introduced in the format as it was measured in the field and it helps the users to avoid errors by graphing the data in real-time. The program allows calculating the true displacement from a marker and fault striae, or from two markers when there are no striae. The solution algorithm is completely different from version 1.0, with a more general approach and the calculation of errors was improved by using a Monte Carlo method. We find TruDisp 2.0 to be more robust and amenable for users than its previous version.