Geomechanical modelling of fault-propagation fold: insights from the role of density on the geometry, and stress and strain evolution, Ayegan anticline, Central Alborz

Fault-related folds extend across most of mountain belts, accretionary prisms, fold-and-thrust belts, and intraplate portions. The widespread importance of such structures in the exploration and extraction of hydrocarbon resources and also seismological aspects had led to consideration beyond the structural geology studies. Numerical modeling of fault-related folds using finite element method can provide valuable information on the stress and strain evolution. In this regard, present study considers the stress and strain evolution of the Aygan fault-propagation fold, which has evolved from footwall shortcut thrusts of the Mosha fault during inversion of the central Alborz basin in Oligocene-Miocene, using finite element method. In the following, the evolution of stress and strain in the Aygan fault-propagation fold considers and analyses using differential stress-strain, strain-time, and stress-time diagrams, and also effects of density change on fold geometry. The modelling results show that increasing and decreasing of density doesn’t play a significant role in stress and strain evolution, so that only slight variations appeared on backlimb. The model results, however, show that increasing and decreasing of density results in increasing and decreasing of half-wavelength, that indicate a direct relationship between density and half-wavelength in the fault-propagation fold.