Understanding the contractional tectonic regime through the sandbox modeling with consistent final length simulation

Sandbox modeling is a physical modeling used to demonstrate the formation of structural geology features in sedimentary basins such as faults or folds. This research conducted to figure out the structure shapes and distributions of the contractional system in generating fault and thrust-related fold. Since we have limited tools, this research conducted in homogen isotropic simulation. This research is divided into three stages, such as preparation, simulation and analysis. In preparation, the quartz sand is colored and dried at room temperature and will be used with Navier-Coulomb rheology and an internal friction angle (φ) of about 30° so it is similar with most sedimentary rock on earth. The sandbox apparatus consists of several main components, namely a glass box, wall, and push lever and designed in the certain dimension of length and sand thickness. The simulation took place with a properly recorded through the time. Seven experiments were carried out using homogeneous sand with a mesh size of 20-30, and the thickness of each layer was the same in one centimeter. Then, different strain changes were produced with an average strain value of 42%, the number of faults, and different fault angles. It concluded that the greater the shortening value, the greater the number of faults formed and the larger the angle of the fault, then most of the experiments resulted in a higher number of thrust faults than back-thrust faults, where the back-thrust fault and synthetic thrust fault were formed simultaneously. The highest layer thickness will always be near the moving wall while the stop wall has the lowest layer thickness. This result will be useful to look for hydrocarbon structural traps in contractional systems. In the future works, suggested to simulate that different sizes of sand can be used, so that it can be seen the influence of grain size on the pattern and distribution of the structure, and morphological variations can be generated.