This project investigates the kinematics and mechanics of oblique convergence and strain partitioning and the geodynamic affects of ridge collision on upper plate deformation subduction zones to gain a better understanding of the formation of fore-arc terranes. This study integrates new and existing GPS data, seismic data (earthquake locations and centroid moment tensor solutions), and geologic observations with numerical models to: 1) estimate the magnitude and spatial variability of coupling on interplate thrust and fore-arc strike-slip faults; 2) determine the rate of fore arc motion; and 3) conduct an analysis of the forces associated with strain partitioning and ridge collision. The study focuses on two convergent margins, southern Central America (Cocos-Nazca-Caribbean plates: Panama) and northern South America (Nazca-South America plates: Ecuador). In southern Central America, Cocos plate convergence is orthogonal and the Cocos Ridge collides with the margin. There is no well-developed margin parallel fore-arc strike-slip fault here and it has been suggested that fore-arc motion to the northwest and southeast is driven by ridge collision. In northern South America, Nazca plate convergence is oblique and the Carnegie Ridge collides with the margin. Margin parallel fore-arc strike-slip faults accommodate northeast motion of the North Andean block. GPS networks will be established in Panama and Ecuador to better constrain the kinematics of surface deformation caused by the interaction of the Cocos and Nazca plates with the Central American isthmus (Caribbean plate) and South American plate. The educational component of this CAREER award : 1) enhances quantitative literacy in the geosciences through the development of six plate tectonics spreadsheet modules whose effectiveness will be assessed; 2) provides international research and education experiences for undergraduate students through the UNAVCO Research Experience in Solid Earth Science for Students and the Penn State University Center for Advanced Undergraduate Studies Experience programs; and 3) provides international research and education experiences for graduate students; 4) forms the basis for new courses on plate boundaries.
Subduction zone plate boundaries release the greatest amount of elastic energy producing great earthquakes and devastating tsunamis. The interaction of plates at subduction zones can be complex where convergence between plates is not orthogonal to the plate margin and where submarine ridges collide. In these cases, motion in the overriding plate can be partitioned between megathrust and strike-slip motion. This study aims determine the forces that control this behavior in two examples in Panama and Ecuador through a combined use of GPS data, which will refine the motion vectors, and modeling to constrain the forces at play. Students will be engaged in the project through classroom activities using the data and through international research experiences. The results of this study will assist in understanding earthquake hazards in Central America.
This research project is supported by the Earth Sciences Division's Tectonics and Education & Human Resources Programs and the Office of International Science and Engineering Americas Program.
