Seismic refraction is a relatively quick and easy way to determine the thickness of the crust.  Click on the below links for tutorials.
Geophysical Exploration
Basic explaination
Encyclopedia

In this case, data from a study conducted in 1965 has been interpreted three different times. Why three times?

• Data quality was fair to poor
• Colorado Plateau is an area of great iinterest, people want to know about the thickness of the crust

Original Study
 

The original experiment went from Hanksville, Utah to Chinle, Arizona  Click here and here to see maps

Three different interpretations of the data:

• Roller 1965
• Prodehl, 1979
• Wolf and Cipar, 1993

Click here to see all interpretations together

Let's put it together,  Click here for conclusions!