For the SEG-EAGE salt data set, common-azimuth migration produces better images in the subsalt than single-arrival Kirchhoff migration, at a similar computational cost. Subsalt reflectors are better imaged and the typical Kirchhoff artifacts caused by severe multipathing disappear. We show how angle-domain Common Image Gathers (CIG) can be easily extracted from prestack wavefield downward conti...

Penelitian ini dilakukan dengan menerapkan metode Amplitude Variance Frequency (AVF) terhadap data Post Stack Time Migration (3D PSTM ) yang diunduh dari laman Wiki SEG secara bebas. Dekomposisi spektral Continuous Wavelet Transform (CWT) untuk mendapatkan nilai frekuensi bervariasi 25 Hz – 70 per 5 seismik sehingga 10 volume iso CWT kemudian digunakan analisis gradien setelah gathering . Anali...

In order to deene an optimal true amplitude prestack depth migration for mul-tishot and multitrace data, we develop a general methodology based on the least squares data misst function associated with a forward model. The amplitude of the migrated events are restored at best for any given geometry and any given preliminary ltering and amplitude correction of the data. The migrated section is th...

Common-image gathers are an important output of prestack depth migration. They provide information needed for velocity model building and amplitude and phase information for subsurface attribute interpretation. Conventionally, common-image gathers are computed using Kirchhoff migration on commonoffset/azimuth data volumes. When geologic structures are complex and strong contrasts exist in the v...

Least-squares reverse-time migration (LSRTM) provides image of reflectivity with high resolution and compensated amplitude, but the computational cost is extremely high. One way to improve efficiency is to encode all of shot gathers into one or several super-shot gathers with designed encoding functions so as to solve a smaller number of wave-equations at each iteration. Another way is to use d...

We demonstrate a method for 2D velocity estimation on real data with no assumption on the re ector geometry nor on the unknown background velocity eld. In the prestack depth migrated volume, locally coherent events are automatically picked without interpretation and characterized by their positions and two slopes. The velocity is estimated by optimizing the atness of these events in the Common ...

We apply 2-D wave-equation prestack depth migration to a North Sea basalt dataset. High velocity and impedance contrasts across a basalt layer causes low P-wave reflection signal-to-noise ratio under the basalt. We first migrate the P-wave data with a provided depth velocity model, and then replace sub-basalt P-wave velocity with a simple estimate of shear wave velocity and migrate locally-conv...

Generalized prestack velocity analysis methods that use an automated approach to resolve laterally variable interval velocity fields are beset by a series of problems. The problem of resolving lateral velocity variations has inherent complications that prevent automated methods from being robust enough to be applied routinely to data from a variety of geologic provinces. The use of automated pr...