Flat spot (reflection seismology)

In reflection seismology, a flat spot is a seismic attribute anomaly that appears as a horizontal reflector cutting across the stratigraphy elsewhere present on the seismic image.

A flat spot can result from the increase in acoustic impedance when a gas-filled porous rock (with a lower acoustic impedance) overlies a liquid-filled porous rock (with a higher acoustic impedance).

It may stand out on a seismic image because it is flat and will contrast with surrounding dipping reflections.

[2] There are a number of other possible reasons for there being a flat spot on a seismic image.

It could be representative of a mineralogical change in the subsurface or an unresolved shallower multiple.