Seismic Tomographic Modeling of the Coast Mountains Batholith, British Columbia, Canada
The Coast Mountains Batholith on the west coast of British Columbia, Canada, comprises a series of granitic to tonalitic plutons. The felsic continental crust is generated from mafic oceanic crust subduction by partial melting and fractionation, leaving ultra-mafic roots. In July of 2009, a sizeable controlled-source experiment was conducted along a 400km east-west transect from Bella Bella into central British Columbia. Student volunteers from multiple universities deployed 1,800 one-component and 200 three-component geophones connected to Texan data recorders with 200-m spacing intervals and shot spacing at 30-km. The 18-point sources ranged from 160 to 1,000 kg of high yield explosives. To analyze this data set, I implemented an enhanced 3-D finite-difference tomography approach for P-wave delays times (Hole, 1992) with a graphical user interface and visualization framework developed by colleagues at UTEP's Cyber-SHARE (Center of Excellence for Sharing Resources for the Advancement of Research and Education through Cyberinfrastructure) facility. In particular, to account for model sensitivity to picked P-wave arrival times, I used a model fusion approach (Olaya et al., 2011) to generate a final model with the lowest RMS residual that combines a set of Monte Carlo sample models. I used visualizations of model perturbation at each iteration to troubleshoot when a model was not converging by highlighting where the RMS residual values were the highest and pinpointing where changes were needed to achieve model convergence. In my final model of the upper mantle using 3-D P-wave tomography, I could not resolve depths below 30km and therefore could not image the ultra-mafic roots of the Coast Mountains Batholith.
Quinonez, Sarah Michelle, "Seismic Tomographic Modeling of the Coast Mountains Batholith, British Columbia, Canada" (2021). ETD Collection for University of Texas, El Paso. AAI28540869.