Update sample results figure for the README

Author: leouieda

README.md

@@ -14,8 +14,13 @@ previous work by the authors and introduces a new density-based discretization a
 to ensure the accuracy of the numerical integration.
 
 ![Neuquén Basin application](neuquen-basin-application.jpg)
-*Application of the methodology to the Neuquén basin in the Andes. The sedimentary
-pack was modeled using an exponential density function.*
+*Application of the methodology to the Neuquén Basin, a foreland basin in the southern
+Andes. (a) Topography of the Neuquén Basin and its location in South America. (b)
+Thickness of the sedimentary basin. Inset shows the exponential density profile used in
+the modeling. (c) Resulting vertical gravitational acceleration at 10 km height modeled
+by tesseroids with exponential density variation in depth. (d) Difference between
+gravitational acceleration modeled using the exponential density profile and a
+homogeneous density.*
 
 ## Abstract