Well, the basic technique is simple enough.
Put down a base layer with a beige or yellowish "parchment colour".
Next, render a texture layer with Filters -> Render -> Clouds -> Plasma, turn it into grayscale with Filters -> Colors -> Colorify and put the layer modus as "Grain Extract."
Ontop of this, put a may layer set to "Screen"
Next, create a new map layer, give it a layer mask, and generate a noisy layer with Filters -> Render -> Clouds -> Plasma.
Make two copies of the resulting layer, and set the layer modus, from bottom to top, to Colour, Burn and Multiply. Adjust the opacity sliders to taste.
Finally, you need to add a layer with the original "city dots".
The fading and crumpling of the edges were done manually and uses the age-old "unsteady human hand" for the effect, so I don't think there's any quick way to automate that.