I’ve been working on a figure that I hope to use for my AGU poster summarizing the effects of slow, shallow basin sediments on crustal thickness measurements using receiver functions. I posted a similar figure in week 7 but it was definitely not “poster quality”. Hopefully this one is more insightful or at least easier to read…
Below is a contour map showing the thickness of the slowest uppermost sedimentary layer of the Illinois Basin. In white are three stations at varying levels of the contour.
a) The P-to-S receiver function moveout curves for each of the three stations. For LD22, the deeper arrivals are shown as a reference. Shallow arrivals are left out because they difficult to distinguish on the moveout curves.
b) Forward modeling of the moveout for the three stations using a simple 4 layer crustal model with 2 shallow layers representing the basin sediments. Arrivals identical to a) are shown for LD22.
c) Shallow (3 km depth) velocity models for the three stations used to make the synthetics in part b). These shallow layers are a simplified representation of the basin sediments.
This figure mostly just shows a trend in the moveout curves that might suggest how the slow sediments are effecting Moho arrivals. From what I’ve gathered so far, the Moho is appearing to arrive later at stations that are above thicker parts of the slow basin sediments. Therefore, the crust may actually be thinner beneath the Illinois Basin than was originally measured. Over the next week, I’ll be applying basin corrections to the velocity models used for my CCP stacks to see how the crustal thickness changes.
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