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Error analysis of the converted wave deduced by equivalent velocity assumption
Wei
Wang
1
,
Yun
Wang
2
4
,
Junjie
Yin
3
and
Xing
Gao
1
1
The State Key Laboratory of Resources and Environmental Information System, Institute of Geographic Sciences and Natural Resources Research, Chinese Academy of Sciences, Beijing 100101, China.
2
Institute of Geochemistry, Chinese Academy of Sciences, Guiyang 550002, China.
3
China United Coal Bed Methane Co., Ltd., Beijing, 100011, China.
4
Corresponding author. Email: yunwang@mail.iggcas.ac.cn
Exploration Geophysics
43(3)
162-170 http://dx.doi.org/10.1071/EG11039
Submitted: 26 July 2011 Accepted: 17 March 2012 Published:
16
May
2012
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Abstract
Based on the assumption of the equivalent velocity and offset, the converted wave travel-time equation, which has a double square root due to the asymmetric ray-path of the down-going P-wave and the up-coming S-wave, can be transformed into a single square root equation if the common scatterpoint (CSP) gathers are binned. This method simplifies the equation and decreases the errors of converted wave migration transferred by P-wave velocity error, compared to the equivalent offset method (EOM) migration proposed by Bancroft, Geiger and Foltinek . In this paper, the errors caused by the introduction of equivalent velocity for the PS-wave are analysed in detail. The discrete errors and effects introduced by discretization of the equivalent offset are presented, and finally the conditions for applying CSP gathers for PS-wave processing under the control of reasonable error limits are derived.
Key words:
converted wave, EOM, equivalent offset, equivalent velocity, error analysis.
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References
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