Probing the “orogenic float” model using teleseismic receiver functions in the northern Canadian Cordillera

English Abstract:

The northern Canadian Cordillera is one of the most actively deforming regions of Canada with some of the largest earthquakes recorded within the last century. Despite its scale (>1000 km in width) and importance in the tectonic evolution of western North America, fundamental questions about its structure and dynamics remain. For example, how is stress transferred from the plate boundary in the southwest to the eastern part of the Cordillera? How is the high elevation isostatically supported? The current model (herein called “orogenic float”), based on numerical modeling, heat flow and GPS data, represents the upper crust as a mobile belt separated from the weak lower crust and “floating” on a hot upper mantle, transferring compressive stresses from the Yakutat collision zone to the Cordilleran Front. However, few seismic studies have been carried out to test this model due to the sparse distribution of broadband seismograph stations in northwestern Canada. In 2013, 7 stations of the Yukon-Northwest Seismograph Network (YNSN) were installed to improve the coverage from seismic stations and address these questions. In this work we will use teleseismic receiver functions to resolve crustal structure across the Cordillera using data from the YNSN and adjacent stations. In particular we will investigate how crustal thickness varies spatially and near major lithospheric sutures (e.g., Tintina fault), and whether or not we can detect the lower crustal detachment zone predicted by the orogenic float model. These data will be compared with those from other regions in order to evaluate the global validity of this model.