This example illustrates this GeoExamples blog entry.
The map is based on the Kartograph software example La Bella Italia, made by Gregor Aisch, and the D3js example La Belle France.
In this case, the filter giving style is better organized and explained in the blog. Basically, the filter stacks a blurred image, a eroded, blurred and substracted image, and the original image.
Modified http://d3js.org/d3.v3.min.js to a secure url
Modified http://d3js.org/topojson.v1.min.js to a secure url
Modified http://d3js.org/colorbrewer.v1.min.js to a secure url
Changed /mbostock/raw/4090846/world-50m.json to a local referenece
https://d3js.org/d3.v3.min.js
https://d3js.org/topojson.v1.min.js
https://d3js.org/colorbrewer.v1.min.js