(7) A simple location map — GMT 5.1.1 documentation

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# (7) A simple location map

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:

    #!/bin/bash
    #		GMT EXAMPLE 07
    #
    # Purpose:	Make a basemap with earthquakes and isochrons etc
    # GMT progs:	pscoast, pstext, psxy
    # Unix progs:	echo, rm
    #
    ps=example_07.ps
    gmt pscoast -R-50/0/-10/20 -JM9i -K -Slightblue -GP300/26:FtanBdarkbrown -Dl -Wthinnest \
    	-B10 --FORMAT_GEO_MAP=dddF > $ps
    gmt psxy -R -J -O -K fz.xy -Wthinner,- >> $ps
    gmt psxy quakes.xym -R -J -O -K -h1 -Sci -i0,1,2s0.01 -Gred -Wthinnest >> $ps
    gmt psxy -R -J -O -K isochron.xy -Wthin,blue >> $ps
    gmt psxy -R -J -O -K ridge.xy -Wthicker,orange >> $ps
    gmt psxy -R -J -O -K -Gwhite -Wthick -A >> $ps << END
    -14.5	15.2
     -2	15.2
     -2	17.8
    -14.5	17.8
    END
    gmt psxy -R -J -O -K -Gwhite -Wthinner -A >> $ps << END
    -14.35	15.35
     -2.15	15.35
     -2.15	17.65
    -14.35	17.65
    END
    echo "-13.5 16.5" | gmt psxy -R -J -O -K -Sc0.08i -Gred -Wthinner >> $ps
    echo "-12.5 16.5 ISC Earthquakes" | gmt pstext -R -J -F+f18p,Times-Italic+jLM -O -K >> $ps
    gmt pstext -R -J -O -F+f30,Helvetica-Bold,white=thin >> $ps << END
    -43 -5 SOUTH
    -43 -8 AMERICA
     -7 11 AFRICA
    END

The same figure could equally well be made in color, which could be rasterized and made into a slide for a meeting presentation. The script is similar to the one outlined above, except we would choose a color for land and oceans, and select colored symbols and pens rather than black and white.

A typical location map.

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

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