DIFFERENCES BETWEEN LAND AND MARINE PROCESSING

land processing is rightly treated as a separate discipline to that of marine processing and, in general, is carried out with separate computer programs and separate personnel. In 2-D marien processing, there is usually a great deal in common with individual lines and often between different areas. Whilst not going quite so far as to define a galactic marine velocity function, it is fair to say that unusual marine processing environments are not common. In the processing of land data, however, quite the reserve is true. Almost every line, and even segments of the same line, can be a law unto themselves. Consequently, land processing is often akin to painstaking detective work.

Despite the great variety of problems that may be encountered in the different environments, three important differences can be identified between land and marine processing. The are:

geometry and statics

sources, receivers and phase

signal to noise

geometry and statics

introduccion

a whole section (3.6) has already been devoted to the subjet of geometry, the essential point being that of irregularity versus regularity. There is anothjer side to this coin, however, that of elevation. This is not normally discussed under the banner of geometry even thought it is, of course, a geometric effect. It is normally introduced under the title of statics and, in particular, field statics. Several excellent references already exist on this topic, so little further will be attempted here save to mention one of them.

The whole point of statics application is to simulate a new set of data from the old set, such that the new set is that set of data which would have been recorded had the source-receiver surface been much smoother and usually flat. Duch a replacement surface is called the datum, and lies below the real acquisition surface. If it is chosen not to be flat for some reason, it is known as a floating datum. Relative to the datum, the seismic data have a more regular structure, free of elevation effects

Fig. 3.97 illustrates this concept.