This project is to model the developments of faults during the bending of the tectonic plate as it approaches a subduction zone. Two dimensional and three dimensional numerical models will be developed using a finite element code. The results of the modeling will be compared to observations of fault patterns observed at subduction zones, mainly the Central America trench where there are plentiful data. Understanding plate strength and how the plate behaves is crucial in geodynamics as convection and energy dissipation on the Earth are mainly driven and caused by subducting oceanic plates.
Broader Impacts This project is to support a postdoctoral researcher and the results will be shared with the MARGINS community and the broader geologic community
Subduction is the process by which one tectonic plate bends beneath another tectonic plate in order to sink into the earth’s interior (the mantle). At the surface the subduction zone is marked by a deep (3-5 km) trench where the plates meet, and a small (200-500 m) rise in topography on the sinking plate where is starts to bend: the outer rise. The bending process stretches the sinking plate causing faults to form. These outer rise faults have been mapped along all the world’s subduction zones. In this study we have reanalyzed the physical properties of these faults, such as their length, spacing, orientation with respect to the trench and location with respect to the trench, and created numerical simulations of a bending, sinking tectonic plate in order to test hypothesis as to the process that control the development of outer rise faults. Our analysis and simulations indicates that outer rise faulting patterns shows that these patterns depend on the age (proxy for thickness and strength) of the sinking plate and its velocity, as well as the magnitude of the force (called slab-pull) pulling the sinking plate into the mantle. Unexpectedly, the patterns are most sensitive to degree of viscous coupling between the two plates in the subduction zone, which changes as a function of time during simulations. In addition, we find that the faulting patterns have little sensitivity to the brittle properties of the plate, as long of those values are within the range observed in natural samples. We conclude that with further simulations of specific regions, the characteristics of outer rise faults can be used as an independent observational constraint on the long term plate boundary coupling, a parameter that is not well-constrained by other observations.
