Refraction mapping of a simple anticline in a high velocity halfspace overlain by low velocity overburden in an analogue model illustrates the conventional refraction method and the behavior of refraction traveltime and amplitude. In addition to first arrivals, the later arrivals on the seismogram, the "multiple refractions," which constitute the P_L mode in the reflection noise problem and long period earthquake seismograms, were studied in detail. In the absence of structure, the behavior of the later refractions on the model agrees with the predicted behavior from exact synthetic refraction seismograms obtained from the computer application of Cagniard's method to a layered half-space. Over the structure, the arrival time and amplitude behavior of the later a rivals is simply diagnostic of the structure.

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