The importance of low-frequency seismic for exploration can be appreciated every time we see the light of day. Thanks to atmospheric gases and other particles that scatter the blues and greens (high frequencies) toward us we see the blue sky instead of the darkness of space as we would on the moon. We see a reddish sky during sunrise and sunset again because blue and green colors are scattered away while the red and orange (low frequencies) stay on course along the atmospheric journey to reach us. The same concept applies to the illumination of subsalt reflectors, only now the propagation path is two-way. The low frequencies survive the torturous scattering by the rugosity of salt surfaces and other shallower inhomogeneities, carrying information about deep reflectors to the surface.

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