(7) A simple location mapΒΆ

Many scientific papers start out by showing a location map of the region of interest. This map will typically also contain certain features and labels. This example will present a location map for the equatorial Atlantic ocean, where fracture zones and mid-ocean ridge segments have been plotted. We also would like to plot earthquake locations and available isochrons. We have obtained one file, quakes.xym, which contains the position and magnitude of available earthquakes in the region. We choose to use magnitude/100 for the symbol-size in inches. The digital fracture zone traces (fz.xy) and isochrons (0 isochron as ridge.xy, the rest as isochrons.xy) were digitized from available maps [1]. We create the final location map with the following script:

#!/usr/bin/env bash
# Purpose:	Make a basemap with earthquakes and isochrons etc
# GMT modules:	coast, legend, text, plot
gmt begin ex07
	gmt coast -R-50/0/-10/20 -JM9i -Slightblue -GP26+r300+ftan+bdarkbrown -Dl -Wthinnest -B --FORMAT_GEO_MAP=dddF
	gmt plot @fz_07.txt -Wthinner,-
	gmt plot @quakes_07.txt -h1 -Sci -i0,1,2+s0.01 -Gred -Wthinnest -l"ISC Earthquakes"+s0.08i
	gmt plot @isochron_07.txt -Wthin,blue
	gmt plot @ridge_07.txt -Wthicker,orange
	gmt legend -DjTR+o0.2i -F+pthick+ithinner+gwhite --FONT_ANNOT_PRIMARY=18p,Times-Italic
	gmt text -F+f30,Helvetica-Bold,white=thin <<- END
	-43 -5 SOUTH
	-43 -8 AMERICA
	 -7 11 AFRICA
gmt end show

Here a simple one-liner creates a simple legend in the upper-right corner.


A typical location map.

[1]These data are available on CD-ROM from NGDC (www.ngdc.noaa.gov).