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GCChronostratigaphic Surfaces and Seismic Reflections*
By
Bob A. Hardage1, Randy L. Remington1, and Paul E. Murray1
Search and Discovery Article #40212 (2006)
Posted October 5, 2006
*Adapted from the Geophysical Corner column, prepared by the authors and entitled, “Reflections Have a ‘Tipper Point’,” in AAPG Explorer, September, 2006. Editor of Geophysical Corner is Bob A. Hardage. Managing Editor of AAPG Explorer is Vern Stefanic; Larry Nation is Communications Director.
1Bureau of Economic Geology, Austin, Texas ([email protected] )
General Statement
A fundamental premise of seismic stratigraphy is that seismic reflections follow chronostratigraphic surfaces, not lithostratigraphic surfaces.
In 1993, Tipper published an intriguing paper
(Geological Magazine, v. 130, no. 1, p. 47-55) in which the following question
was posed: “Do seismic reflection events necessarily follow chronostratigraphic
surfaces?” Simple earth
models and forward seismic
modeling
were used to
illustrate basic and important interpretation principles.
The editor of this monthly column (Hardage) has observed increased interest in seismic interpretation among graduate students when they have been asked to analyze this Tipper paper, so repeating some of its concepts here seems appropriate.
uGeneral statementuFigure captionsuModelsuConclusionuAcknowledgement
uGeneral statementuFigure captionsuModelsuConclusionuAcknowledgement
uGeneral statementuFigure captionsuModelsuConclusionuAcknowledgement
uGeneral statementuFigure captionsuModelsuConclusionuAcknowledgement |
Stratigraphic and Seismic Models We use the stratigraphic model in Figure 1 as a demonstration. This model shows five units deposited at five different geologic times -- T1 through T5. These five chronostratigraphic bodies are shown in the top panels of Figures 2, 3, and 4 as stacked, overlapping targets that are to be imaged. This five-layer stack is then illuminated with seismic wavelets having varying resolution properties.
In these figures, the left column shows the
illumination created by a high-resolution wavelet; the center column
uses a moderate-resolution wavelet for the
Relationships between wavelet length, bed
thickness, and bed spacing are defined at the top of each column. The
amount of unit-to-unit overlap decreases as
What does this
In this case, the seismic reflection response is a diachronous event, not a chronostratigraphic event. We lose the ability to analyze the internal architecture of the layered system, and seismic reflections no longer follow chronostratigraphic surfaces.
Even though the ConclusionWhether seismic reflections follow chronostratigraphic surfaces depends on:
Probably all reflection possibilities illustrated in these models occur within any single 3-D seismic volume. Our recommendation is that the premise that seismic reflections follow chronostratigraphic surfaces is sound and should be applied as a first principle of seismic interpretation.
However, in critical prospect areas,
Tipper, John C., 1993, Do seismic reflections necessarily have chronostratigraphic significance?: Geological Magazine, v. 130, p. 47-55.
Documenting principles of elastic-wavefield seismic stratigraphy such as this example has been funded by DOE/NETL. |