GNGTS 2024 - Atti del 42° Convegno Nazionale

Session 1.3 GNGTS 2024 A dynamic identfcaton of contnuous discontnuites in geodynamic numerical models V. Fedeli 1 , A.M. Marota 1 1 Dipartmento di Scienze della Terra “Ardito Desio” (Università degli Studi di Milano, Italy) Discontnuites afect the Earth’s dynamics, yet the Earth is ofen represented in geodynamical models as a contnuous material. The challenge of representng discontnuites in numerical models has been addressed in several ways in literature. The split node method, originally introduced by Jungels (1973) and Jungels and Frazier (1973) for elastc rheology and then modifed by Melosh and Raefsky (1981) to simplify its implementaton, allows the introducton of discontnuity into a fnite element model by imposing an a-priori slip at a designated node, where the displacement depends on the element which the node is referred to. Originally, this method requires that the discontnuity’s geometry and slip are pre-established. More recently, Marota et al. (2020) modify this approach by introducing a coupling factor that indicates the percentage diference between the velocites of the element to which the slip node belongs, while the velocity consistently derives from the dynamic evoluton of the system. However, this method stll requires the pre-establishment of the discontnuity’s geometry. We here present a new technique that enables the dynamic identfcaton of the discontnuity’s during the thermomechanical evoluton of the system, based on physical parameters and without predefning the slip or the geometry. We have implemented a new algorithm that identfes one or more discontnuites in a fnite- element scheme operatng through two phases: nucleaton and propagaton. Nucleaton involves selectng a yield physical property and identfying the potental slip nodes, i.e., nodes on which the chosen physical property exceeds a yield value. The nucleus is then identfed as the potental slip node where the chosen property most exceeds the yield. Propagaton can be performed by choosing between three approaches of propagaton: single simple fault, multple simple fault and single double fault; and three schemes for the identfcaton of neighboring nodes: grid-bounded, pseudo-free and free. The resultng discontnuity is the line connectng the nucleus and the propagaton nodes. Once the discontnuity has been identfed, a coupling factor is introduced and the algorithm contnues to operate following the Marota et al., (2020)’s scheme. The results of several benchmark tests, performed through both simple and complex fnite- elements models, confrm the success of the algorithm in recognizing yield conditons and introducing a discontnuity into a fnite-element model and demonstrate the correctness of the propagaton’s geometry.