pre-stack time migration, a misunderstanding

Oil and natural gas exploration -- geology and geophysics
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jefry123
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pre-stack time migration, a misunderstanding

Post by jefry123 »

I am dealing with prestack time and depth migrations. There are some ambiguities which I hope to understand step by step. I would be grateful if you could help me with this.

Somewhere I read that "it is a misconception that people think PSTM is done in time domain and PSDM in depth domain, while both of them are done in depth domain". I know that the prestack depth migration is done by reconstruction of the upgoing and downgoing waves in depth and then applying some imaging condition. However, I want to realize that why it is said that PSTM is also in depth!

Softwares use RMS velocity and x-t domain data as inputs and produce time gathers/section as output. Is it how PSTM handle the data or it transform the output from x-z to x-t?

Using https://wiki.seg.org/wiki/Prestack_time_migration as a reference to my questions:

Equation 32 states the traveltimes from source to scatter point and then to receiver point. It has a term z for depth. Could it be the reason they say PSTM is done in depth domain?

In equation 35, the famous double square root equation, the z term is replaced for time tau using z = vt/2. According to https://csegrecorder.com/articles/view/ ... g-prestack this v is the RMS velocity, but can we use z=vt/2 with a RMS velocity or it should be an interval velocity?

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