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An interactive solution for resolving mid-wavelength statics anomalies

Geophysical Data Systems, Moscow, Russia

Corresponding author: ilya@gds.ru

The first 20% of the full text of this article appears below.

Automatic methods used in conventional seismic data processing to make statics corrections work well with short-wavelength anomalies but regularly fail to resolve mid-wavelength near-surface anomalies. Calculation of correct static time delays caused by near-surface heterogeneities is especially difficult when the heterogeneities extend from half of a spread length to 2–3 times the source-receiver offset.

In this case, obtaining information about surface conditions, the near surface, and the shape of reflectors should be done prior to making static corrections because it is necessary to eliminate any uncertainty regarding those portions of the data that need to be processed with static corrections and those aspects that represent mid-wavelength anomalies. When only limited a priori information is available, some assumptions about near-surface structure and reflector shape are usually made. For this reason, an essential part of many methods to calculate mid-wavelength statics is direct intervention by an interpreting geophysicist, who can accurately assess various sources of information and make relevant assumptions about the near-surface model.

In the method described in this article, the geophysicist delineates zones of near-surface heterogeneities and interactively determines time shifts within their bounds. No assumptions about the near-surface model are made. A model of time shifts, which adequately reflects near-surface heterogeneities, is generated as the result of the correction. The advantage of this approach is obvious—building the time delays model requires less a priori information than the construction of near-surface model.

	Delineation of the near-surface heterogeneity zones

 
The correction starts with reviewing the early arrivals of the recorded seismic wavefield. In many cases, when quantitative interpretation of first breaks is difficult, it is still possible to delineate areas of the near surface which have anomalous characteristics (and therefore will require statics corrections on the data) by examining common-offset sections—a process we call "on-the-fly reviewing" of the data.

Figure 1a shows a common-offset section (900 m) . . . [Full Text of this Article]