Seismic energy that has been reflected more than once. While virtually all seismic energy involves some multiples, the important distinction is between long-path and short-path multiples: a long-path multiple arrives as a distinct event whereas a short-path multiple arrives so soon after the primary that it merely adds tail to the primary (i.e., changes the waveshape).
Short path multiples may obscure stratigraphic detail even where structural aspects are not affected significantly.
The attitude of long-path multiples does not represent the portion of the section associated with their arrival time. Usually long-path multiples have traveled more in the slower (shallower) part of the section than primaries with the same arrival time, so that they ordinarily show more normal moveout and can be attenuated by common-midpoint stacking..