3.3 1-D Synthetic Modeling
To aid in our interpretation, we produced synthetic receiver functions (assuming a ray parameter of 0.05 s/km) that tested three simple velocity-density models of the structure below Kodiak Island. Our primary goal was to evaluate resolution of hypothetical structures near the top of the subducting oceanic crust. To better account for the RF variability across the profile, we selected groups of RFs from three different sections (6 km bins, centered at 10, 22 and 32 km distance along the profile) which showed good signal-to-noise ratios (Fig. 2c) and linearly stacked them. We then used the position of the slab Moho Ps arrival on the resultant stacked traces to help with the construction of the models (Figs. 3a-c).
Model 1 (Table 1; Fig. 3a) was based on the Kim et al. (2014) Kenai Peninsula model beneath the Kenai asperity. The model consists of a featureless upper crust, a 3 km-thick LVZ at the plate interface and an 8 km-thick oceanic crust. For model 2 (Table 1; Fig. 3b), we removed the 3-km-thick LVZ and calculated synthetics using just the featureless upper crust and the 8 km-thick oceanic crust. Model 3 (Table 1; Fig. 3c) is a simple two-layer model with an increase in velocity at the slab Moho depth.