Residual-moveout analysis in presence of strong lateral velocity anomalies

Test data and image

I performed my test on a simple synthetic data set. The data were modeled assuming a strong, and fairly localized, velocity anomaly above a flat reflector. Figure 1 shows the central part of the model. I modeled 400 split-spread shot gathers with offsets ranging from -2 km to 2 km. The source function was a Ricker wavelet with central frequency of 25 Hz.

The localized velocity anomaly caused clear non-hyperbolicity in the data common-midpoint (CMP) gathers. Figure 2 shows two typical CMP gathers in the data set. Figure 2a shows the CMP gather at horizontal location X=0 km; that is, in the middle of the model, and Figure 2b shows the CMP gather at X=.55 km. The non-hyperbolicity in the CMP gathers makes this a challenging data set for velocity methods that characterize moveout with one-parameter curves.

Vel-overn Figure 1. Central part of the velocity model used to model the data.

Data-all-overn Figure 2. Two typical CMP gathers in the data set: a) X=0 km, and b) X=.55 km.

Residual-moveout analysis in presence of strong lateral velocity anomalies