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added Category:Treatise Handbook 3 using HotCat
| part = Predicting the occurrence of oil and gas traps
| part = Predicting the occurrence of oil and gas traps
| chapter = Evaluating top and fault seal
| chapter = Evaluating top and fault seal
| frompg = 10-1
| frompg = 10-51
| topg = 10-94
| topg = 10-52
| author = Grant M. Skerlec
| author = Grant M. Skerlec
| link = http://archives.datapages.com/data/specpubs/beaumont/ch10/ch10.htm
| link = http://archives.datapages.com/data/specpubs/beaumont/ch10/ch10.htm
[[:file:evaluating-top-and-fault-seal_fig10-38.png|Figure 1]] is a simple [[cross section]] of a low-relief salt structure showing three seismic sequences. The figure shows how strain is calculated: by comparing the original undeformed line length with the deformed line length between two arbitrary points, A and B. In this figure, 1<sub>0</sub> is the initial, undeformed line length; 1<sub>1</sub> is the deformed line length of the 60-m.y sequence boundary; and 1<sub>2</sub> is the deformed line length of the 131-m.y. sequence boundary. The strain (ε) on the 131-m.y sequence boundary is ε = (1<sub>2</sub> – 1<sub>0</sub>)/1<sub>0</sub> = 2.5%. The strain on the 60-m.y. sequence boundary is ε = (l<sub>1</sub> – 1<sub>0</sub>)/1<sub>0</sub> = 0.5%. All strains are extensional.
[[:file:evaluating-top-and-fault-seal_fig10-38.png|Figure 1]] is a simple [[cross section]] of a low-relief salt structure showing three seismic sequences. The figure shows how strain is calculated: by comparing the original undeformed line length with the deformed line length between two arbitrary points, A and B. In this figure, 1<sub>0</sub> is the initial, undeformed line length; 1<sub>1</sub> is the deformed line length of the 60-m.y sequence boundary; and 1<sub>2</sub> is the deformed line length of the 131-m.y. sequence boundary. The strain (ε) on the 131-m.y sequence boundary is ε = (1<sub>2</sub> – 1<sub>0</sub>)/1<sub>0</sub> = 2.5%. The strain on the 60-m.y. sequence boundary is ε = (l<sub>1</sub> – 1<sub>0</sub>)/1<sub>0</sub> = 0.5%. All strains are extensional.
This method provides both an estimate of quantitative strain and the timing of strain. The incremental strain is the strain occurring during the time interval between two sequence boundaries. In the preceding figure, 0.5% strain occurred between 60 Ma and the present, while 2.5% strain occurred between 131 Ma and the present. Consequently, 2.0% strain occurred between 60 and 131 Ma. Strain–time plots display the strain affecting the top seal from the onset of deformation to the present.
This method provides both an estimate of quantitative strain and the timing of strain. The incremental strain is the strain occurring during the time interval between two sequence boundaries. In the preceding figure, 0.5% strain occurred between 60 Ma and the present, while 2.5% strain occurred between 131 Ma and the present. Consequently, 2.0% strain occurred between 60 and 131 Ma. Strain–time plots display the strain affecting the top seal from the onset of [[deformation]] to the present.
==Correction for compaction==
==Correction for compaction==
Analysis requires decompaction of the sediments to correct for the apparent strain caused by compaction. In the Central Graben, the effect is generally minimal.
Analysis requires [[decompaction]] of the sediments to correct for the apparent strain caused by compaction. In the Central Graben, the effect is generally minimal.
==Empirical threshold for top seal failure==
==Empirical threshold for top seal failure==
[[Category:Predicting the occurrence of oil and gas traps]]
[[Category:Predicting the occurrence of oil and gas traps]]
[[Category:Evaluating top and fault seal]]
[[Category:Evaluating top and fault seal]]
[[Category:Treatise Handbook 3]]