FIG. T-8. (a) Refraction time-distance curves RA,RB=reflections from A,B. HA,HB=head waves at A,B. WA, WB=wide-angle reflections from A,B. (b) Wavefront diagram showing first arrivals. (c) Wavefront diagram showing first arrivals from an idealized salt dome. (d) Composite time-distance curves (dashed lines) constructed from arrival curves from sources 1, 2, 3, 4, and 5 (solid lines). Refraction portions from sources 2, 3, and 4 have been displaced upward to show the ‘‘equivalent arrival times’’ as if the profiles from these sources had been longer. Such displaced curves should overlap for confidence and show the same reciprocal time tr. Actual time-distance curves from these sources might have been different if another refractor had been reached (e.g., dotted lines).