INCORPORATING TEMPORAL CHANGES IN MATERIAL PROPERTIES INTO ANALOG MODELING

Physical analog modeling is often used to replicate crustal and lithospheric changes to reconstruct the structural evolution of a region. These analog models are divided into three approaches; 1) a closed (or internally driven) system, where no external velocities, forces, or materials are added; 2) an open (or externally driven) system, where deformation is primarily driven by externally applied forces; 3) a combined system, where deformation is driven by both externally applied forces and the internal forces of the material.

We developed a combined approach analog modeling apparatus using wet clay as the deformational medium. While the use of granular media (e.g. sand) is more commonly used in physical models, wet clay has several advantages. Wet clay (such as kaolinite) produces clear fault/fracture surfaces during deformation and its volume and mechanical properties are capable of changing with varying water content. Furthermore, while most external or combined force analog models using dry granular media or wet clay operate under relatively high rates of strain (even for laboratory strain rates), we wanted to be able to utilize a relatively low strain rate by employing geared stepper motors. This allows for autonomous operation of the model for long periods of time to achieve the desired low strain rates.

By utilizing a flexible, combined approach model, we can tackle a broad range of questions related to variable strain rates, volumes, and material properties (e.g. plasticity, strength). This flexibility will allow us to investigate the geologic structures created in a variety of settings. In addition, our model was constructed at a relatively low cost using off the shelf parts, materials, and preexisting code libraries, making this an excellent teaching and research tool for the undergraduate setting.