New Mexico Tech
Earth and Environmental Science

ERTH 401 / GEOP 501 - Computational Methods & Tools

Lab 14: GMT Part 2

Today's lab will use some of the more complex options in the Generic Mapping Tools we discussed in lecture today.

As with last week, we'll all log on to a common linux machine to ensure the same version. Instructions from last week still hold, and are repeated here. First, open up a terminal window on whatever machine you choose to use (doesn't matter Mac or Linux box). We'll then SSH into the Linux machine --- will give these instructions during the lab period, or email one of us for instructions. Once you are logged in, please change directories (cd) into the directory called your first name. This directory will be your operating space for the next two labs. Copy over the files that are currently held in /home/geop501/files_2 as you'll use these in the exercises:

  $>cp /home/geop501/files_2/* . 
  

For reference -- GMT documentation pages: here. Use those regularly to explore the modules you'll need and examples on their use.

Exercise 1: Plot other geologic/geophysical datasets

In this exercise, we've provided a version of global sediment thickness in a grid file able to be read by GMT. The data is average sediment thickness (in m) within a 5 minute cell, and more information for this dataset is available here NGDC sediment data.

Deliverable 1: Use GMT to plot sediment thickness

For all deliverables, please turn in your GMT scripts, any datafiles used, and the resulting plots. All files should be names with your last name and the deliverable number. For deliverable 1 make a plot of sediment thickness in the Gulf of Mexico using a reasonable color palette. Include a map scale, a color scale bar, and a title for the plot.

Exercise 2: Use GMT to plot bathymetry with illumination

For this section, work with the grd file from last week (earth_relief_05m.grd). For the first part of this exercise, make a map of the region (latitude range: 11.5 N to 6.5 N, longitude range: 88 W to 83 W) using a reasonable color map for the bathymetry and topography. You should see the effect of resolution on that image. For the other maps, use a different grd file - this one extracted for this region from the higher resolution etopo1 dataset. Using this higher resolution grid, make 2 maps, one without illumination, and one with illumination from the northwest.

Deliverable 2: Illuminated map

Three maps of the latitude range: 11.5 N to 6.5 N, longitude range: 88 W to 83 W. First using earth_relief_05m.grd, second using etopo1_deliverable2.grd without illumination, and third, using etopo1_deliverable2.grd with illumination.

Exercise 3: Use GMT to plot data in xyz format

In this section, you will work with data contained in a data table which you will need to plot in GMT. The data in this case is latitude, longitude, and depth (km) for the position of the subducted slab off the Pacific Northwest of the US. Source of the data is the USGS Slab 1.0 model. Your task here is to use tools in GMT to convert this data to a grid format and plot the top of the subducted slab on a regional map.

Deliverable 3: Map of Cascadia slab position

Produce a map of slab position in the Pacific Northwest. Use a latitude range of 52N-40N and a longitude range of -130 to -120. Make sure to include a color scale bar and a title for the plot.

Exercise 4: Combine datasets

A very useful skill is to make maps in GMT with a combination of different datasets; it allows you to explore possible relationships that make for interesting scientific exploration. Remember that you can layer multiple datasets into your basemap, so adding various datasets is not terribly difficult once you have the data in the proper formats.

For this section, continue working with the Cascadia slab map made for Deliverable 3. We'd like you to also add to it the bathymetery and topography, sediment thickness, and location of seismic stations in the area. For the seismic stations, you can use this iris webservices link. If you are more interested in how that link works - go here ... it's a great way to get access to the seismic data available.

Deliverable 4: Cascadia Map with variety of datasets

Produce a map of slab position, background topography and bathymetry, sediment thickness, and seismic stations operating in the Pacific Northwest. Use the basemap from Deliverable 3, but add the other datasets in reasonable ways (you'll need to think about and experiment with what makes a readable map). Include relevant scale bars, legends, and a title for the plot.