Loading of the data/conversion Demultiplexing Editing Geometry Amplitude correction Frequency filter Deconvolution Velocity analysis NMO/DMO-Correction Stacking Migration Measurements Navigation Printing/storage CMP-Sorting Prestack Poststack Post-processing Pre-Processing Basic scheme of the seismic data processing

DMO (Dip move-out) A seismic processing operation to correct for the fact that, for dipping reflections, the traces of a CMP gather do not involve a common reflection point. DMO effectively corrects for the reflection-point smear that results when reflectors dip. Events with various dips stack with the same velocity after DMO. (DMO can be performed in a number of ways) Sheriff, 1991

Horizontal Reflector CMP = CDP CMP  CDP Dipping Reflector CMP = common mid point CDP = common depth point Dip move out (DMO)

Loci of reflection points Zero offset: coincident Source (S) and geophone (G) Common offset: offset between Source (S) and geophone (G) Show possible reflection points for one particular traveltime

DMO correction NMO: coordinate transformation from A (y n,t) to B (y n, t n ) DMO: coordinate transformation from B (y n,t n ) to C (y 0 -  0 ) Zero-offset migration: coordinate transformation from C (y 0 -  0 ) to D (y m, 

Dip Move out (DMO)

Marine line over a salt structure Cases of conflicting dip Analysis of data without DMO correction Analysis of data with DMO correction (following pictures are obtained from Yilmaz, 2001)

Selected CMP gathers from a 2D marine dataset Yilmaz, 2001 NMODMONMO -1

Velocity spectrum Without DMO correction (smearing of data) With DMO correction Yilmaz, 2001

Close-up view of the velocity spectrum and CMP gather Without DMO correction Yilmaz, 2001

Close-up view of the velocity spectrum and CMP gather With DMO correction Yilmaz, 2001

Velocity field used to stack the CMP gathers Without DMO correctionWith DMO correction Yilmaz, 2001 With DMO: less smearing: more detailed velocity field

NMO correction of DMO corrected gathers Without lateral varying and with lateral varying velocity Yilmaz, 2001

Field example of DMO correction NMO Stacking Migration DMONMO -1 NMO CMP stack DMO stack Migrated CMP stackMigrated DMO stack

CMP stack and DMO stack Yilmaz, 2001 Amplitudes of reflections off the flanks of the salt have similar amplitude as flat events

Comparison between Migration of CMP stack and DMO stack Yilmaz, 2001 Amplitudes of reflections off the flanks of the salt have higher amplitude

Time migration of CMP and DMO stack Yilmaz, 2001