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A two-dimensional analog model with a cylindrical structure has been constructed to simulate the simple refraction problem. Experimental seismograms showing the first refraction are presented. From such records traveltime curves are constructed. The structure, as predicted, appears as an anomaly in the traveltime. Plots showing refraction amplitude versus distance also show an anomaly in the neighborhood of the structure.

A number of other coherent events appear on the experimental seismograms, all exhibiting the horizontal velocity of the refractor. These are shown to be refracted reflections and reflected refractions, many of which contain compressional-to-shear conversions. The structural significance of these later events is shown by traveltime anomalies and amplitude anomalies similar to those for the first refraction.

Finally, a brief discussion of the shallow refractor problem is included. In this case, the traveltime difference between the multiple refractions is small, so the seismogram has a ringing, “mode” structure.

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