10,323
edits
Changes
Jump to navigation
Jump to search
Line 53:
Line 53: − − [[file:seismic-migration_fig5.png|left|thumb|{{figure number|5}}(a) CMP stack showing reffections from a salt dome in the Gulf of Mexico. (b) Stack after DMO processing. Steep portions of diffractions and reflections are now preserved. (c) Migration of the DMO-processed data shows the steep flank of the salt dome to be a particularly strong reflector.]] Line 63:
Line 61: − + − [[file:seismic-migration_fig6.png|thumb|{{figure number|6}}(a) Unmigrated and (b) migrated stack of DMO-processed data from the Gulf of Mexico.]]+ + +
no edit summary
Each of the different approaches has specific advantages such as computational efficiency, accuracy for imaging steep reflectors, and accuracy in the presence of spatial variation of velocity. Likewise, each can produce undesirable processing artifacts related to some limitation in data quality such as poor signal to noise ratio, too coarse a spatial sampling interval, and missing data (e.g., due to seismic source misfires).
Each of the different approaches has specific advantages such as computational efficiency, accuracy for imaging steep reflectors, and accuracy in the presence of spatial variation of velocity. Likewise, each can produce undesirable processing artifacts related to some limitation in data quality such as poor signal to noise ratio, too coarse a spatial sampling interval, and missing data (e.g., due to seismic source misfires).
==Velocity: the key parameter==
==Velocity: the key parameter==
==Poststack versus prestack migration==
==Poststack versus prestack migration==
<gallery mode=packed heights=200px widths=200px>
seismic-migration_fig5.png|{{figure number|5}}(a) CMP stack showing reffections from a salt dome in the Gulf of Mexico. (b) Stack after DMO processing. Steep portions of diffractions and reflections are now preserved. (c) Migration of the DMO-processed data shows the steep flank of the salt dome to be a particularly strong reflector.
seismic-migration_fig6.png|thumb|{{figure number|6}}(a) Unmigrated and (b) migrated stack of DMO-processed data from the Gulf of Mexico.
</gallery>
While migration algorithms are capable of accurately imaging reflections from steep interfaces, shortcomings in CMP stacking lead to destruction of such reflections before conventional ''poststack migration'' is applied. Two alternatives to poststack migration of CMP stacked data preserve reflections from steep interfaces. Migration can be applied to the unstacked data (so-called ''prestack migration'') so that the data need not be reduced to an approximation to zero offset before migration. The improvement in imaging of steep reflectors by this approach, however, is bought at the price of a great increase in the amount of computation required for the migration.
While migration algorithms are capable of accurately imaging reflections from steep interfaces, shortcomings in CMP stacking lead to destruction of such reflections before conventional ''poststack migration'' is applied. Two alternatives to poststack migration of CMP stacked data preserve reflections from steep interfaces. Migration can be applied to the unstacked data (so-called ''prestack migration'') so that the data need not be reduced to an approximation to zero offset before migration. The improvement in imaging of steep reflectors by this approach, however, is bought at the price of a great increase in the amount of computation required for the migration.