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Figure 1 – (a) Absolute magnitude of seismic amplitude along image coordinate X. A seismic bright spot occurs between coordinates X1 and X4. Absolute magnitude is always a positive quantity. (b) First derivative of the amplitude function, which has positive and negative values. (c) Second derivative of the amplitude function, which also has positive and negative values. Note how the extrema in (c) define the edges of the amplitude anomaly.