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The AAPG/Datapages Combined Publications Database

AAPG Bulletin

Abstract


Volume: 66 (1982)

Issue: 10. (October)

First Page: 1685

Last Page: 1686

Title: Weathering Statics Problem and First-Arrival Time Surfaces: ABSTRACT

Author(s): Joong H. Chun, Chester A. Jacewitz

Article Type: Meeting abstract

Abstract:

Where organized by shot and receiver coordinates, the collection of picks of the first arrivals forms a jagged surface. It is thus crucial that the properties of the time surface of first arrivals be studied for various situations. It is particularly useful to

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analyze two projections of the time surface: one to a constant shot plane and one to a constant receiver plane. For each fixed shot or receiver, there is a distribution of time picks. Comparisons with real data distributions show a good match to theory as the time surface is manipulated. The study of these projections enables us to derive criteria for estimating the accuracy, precision, and consistency of any solution to the statics problem for the simple model of a Previous HitlinearNext Hit Previous HitrefractorNext Hit and high frequency statics. In this case the specific criteria are: (1) the expected value of each distribution is constant along each axis, (2) the variance of each distribution is zero along both shot and receiver axes, and (3) the shot and receiver statics are equal.

In addition, several basic types of anomalies can be recognized by their effects upon the first-arrival time surface. These basic types are: (1) geometric variation in the Previous HitrefractorNext Hit, (2) Previous HitvelocityNext Hit variation in the weathering, and (3) Previous HitvelocityTop variations in the subweathering. The combination of these three is a complete description of the general weathering statics problem.

The effects of these anomalies may be studied via the shot and receiver projections. Type (1) can lead to a blurring of the first-arrival time distribution. Type (2) can lead to a lens shape within the first-arrival projections. The lens is formed by a splitting of the left-hand and right-hand shots. Since the lens is composed of both time-rise and time-fall segments, it will be split under certain circumstances. Type (3) can appear as a change in the trend of the projections and a discrepancy between shot and receiver statics.

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