I need to know how to calculate paleostress direction during faulting, any formulas or something.
thanks for your attention
Davit Maqadze in Petrel software there is a workflow that allows you to calculate paleostresses on faults and fractures. First you will need to have them in 3D and the next strep is to classify your features, have they all occurred during the same event? or you have multiple events overlapping. A second layer of classification and more simple is based on dip angle as well. Once you do that you run the simulation and it will do 1000 iterations and provide you a probability distribution plot showing you the possible tectonic stresses responsible for the creation of these features. The point with the highest probability is your paleostress.
There are many programs you can use for paleostress analysis, like Win-Tensor, TectonicsFP, T-Tecto, Multiple Inverse Method, TR method etc. But you have to be very careful with the way you handle your data. Using fault-slip data from multiple deformational events (activated by different stress tensors) without any separation could result in not trustworthy results.
I recommend the inversion method proposed by Michael, 1984; 1987. You can use faults of multiple orientations but the stress regime should be uniform. You can also estimate the confidence region for the best fit stress tensor using bootstrap resampling method.
Paleofault plane solutions yield paleostress directions (e.g. T,P stress axes). Take a look at Beard et.al.(2010)
Dear Davit Maqadze,
The major step of a tectonic study is done in the field with measurements of striated fault planes (direction, dip, fault movement and pitch of stria), tension gashes and other brittle structures... The separation and chronology of the different tectonic stages is based on fault planes intersections, superposition of several striae on the same fault slickenside, incompatibility of the movements of parallel faults, the presence of synsedimentary faults, the age of the deformed geological formations… After measuring the fault and fracture data in the field, paleostress analysis and stress tensor calculations are done through a software with a detailed calculation method (e.g., Win-Tensor software). Then, the obtained paleostress configurations are separated and deciphered using field observations, comparisons with previous studies and regional tectonic events.
I would like to recommend the software MSATSI (Martínez-Garzón et al., 2014, Article MSATSI: A MATLAB Package for Stress Inversion Combining Soli...
), although it's a package used for stress field inversion from the focal mechanisms. Actually, the fault structure also can depict the fault slip (strike, dip, slip direction) similar to the focal mechanism, which means this software also can invert the paleo stress field from fault structures.- Badges
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