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From: Nicholas Kinar on 14 Mar 2010 13:23
Hello--

I would like to generate a synthetic seismic trace using the real-valued
Ricker wavelet. (Other wavelets could also be used.) Normally I think
that this should involve a convolution operation. However, I would like
to ensure that the synthetic trace has a constant (and known) Q-value.

I would like to find a monograph/book/paper or some other type of
procedure to efficiently generate this synthetic trace. Any suggestions?

From: Rune Allnor on 14 Mar 2010 13:41
On 14 Mar, 18:23, Nicholas Kinar <n.ki...(a)usask.ca> wrote:
> Hello--
>
> I would like to generate a synthetic seismic trace using the real-valued
> Ricker wavelet.  (Other wavelets could also be used.)  Normally I think
> that this should involve a convolution operation.  However, I would like
> to ensure that the synthetic trace has a constant (and known) Q-value.
>
> I would like to find a monograph/book/paper or some other type of
> procedure to efficiently generate this synthetic trace.  Any suggestions?

Seismic traces are usually modeled using some Finite
Difference or Ray Tracing scheme. Either way, the
constant Q question is irrelevant, as all kinds of
physical effects mess the signal up.

Decide on a Ricker wavelet and use it. No need to
fuzz things up with Q values; you will have more
than enough other stuff to worry about.

Rune
From: Nicholas Kinar on 14 Mar 2010 14:10
Hello Rune--

Thank you for your response.

>
> Seismic traces are usually modeled using some Finite
> Difference or Ray Tracing scheme. Either way, the
> constant Q question is irrelevant, as all kinds of
> physical effects mess the signal up.
>
> Decide on a Ricker wavelet and use it. No need to
> fuzz things up with Q values; you will have more
> than enough other stuff to worry about.

Yes - you are right about the physical effects, and this is what I would
normally do if I wanted a "realistic" seismic trace: use
finite-difference or ray-tracing algorithms.

However, I am reading a book "Seismic Inverse Q Filtering" by Y. Wang,
and the author describes how to build an extremely simple seismic trace
with a known Q value to test an inverse seismic Q filtering algorithm.

The idea is to generate a (non-realistic) simple seismic trace. I've
tried to implement this algorithm, but I find that some of the salient
details of the implementation are tricky.

Could I send you some further information via e-mail to read? Then
perhaps we could summarize on the newsgroup what would be required to
fully implement this synthetic algorithm.

Thanks Rune.
From: Rune Allnor on 14 Mar 2010 15:54
On 14 Mar, 19:10, Nicholas Kinar <n.ki...(a)usask.ca> wrote:
> Hello Rune--
>
> Thank you for your response.
>
>
>
> > Seismic traces are usually modeled using some Finite
> > Difference or Ray Tracing scheme. Either way, the
> > constant Q question is irrelevant, as all kinds of
> > physical effects mess the signal up.
>
> > Decide on a Ricker wavelet and use it. No need to
> > fuzz things up with Q values; you will have more
> > than enough other stuff to worry about.
>
> Yes - you are right about the physical effects, and this is what I would
> normally do if I wanted a "realistic" seismic trace: use
> finite-difference or ray-tracing algorithms.
>
> However, I am reading a book "Seismic Inverse Q Filtering" by Y. Wang,
> and the author describes how to build an extremely simple seismic trace
> with a known Q value to test an inverse seismic Q filtering algorithm.
>
> The idea is to generate a (non-realistic) simple seismic trace.  I've
> tried to implement this algorithm, but I find that some of the salient
> details of the implementation are tricky.
>
> Could I send you some further information via e-mail to read?

No.

> Then
> perhaps we could summarize on the newsgroup what would be required to
> fully implement this synthetic algorithm.

Just browsing the table of contents of the book,

http://www.amazon.com/Seismic-Inverse-Filtering-Yanghua-Wang/dp/1405185406/ref=sr_1_1?ie=UTF8&s=books&qid=1268595741&sr=8-1#reader_1405185406

sends cold shivers down my spine. The author's premise seems
to be that there exists 'a' mathemathical model that influences
the Q factor of the trace. Then he goes on to list almost a
dozen different models for the effect (see the list of subchapters
in chapter 3). That alone sets off all the alarms in my mind.

I used to do those kinds of things ages ago and my experience
is that the earth is a random medium in every sense of the
word. Unless you sample it directly - drill a hole and
dig stuff out of it - one does not know much. While any of
the proposed models might be defended in one setting, the
reality is that there are gazillion other situations in the
same survey where the model is invalid.

Rune
From: Nicholas Kinar on 14 Mar 2010 16:16
>
> Just browsing the table of contents of the book,
>
> http://www.amazon.com/Seismic-Inverse-Filtering-Yanghua-Wang/dp/1405185406/ref=sr_1_1?ie=UTF8&s=books&qid=1268595741&sr=8-1#reader_1405185406
>
> sends cold shivers down my spine. The author's premise seems
> to be that there exists 'a' mathemathical model that influences
> the Q factor of the trace. Then he goes on to list almost a
> dozen different models for the effect (see the list of subchapters
> in chapter 3). That alone sets off all the alarms in my mind.
>
> I used to do those kinds of things ages ago and my experience
> is that the earth is a random medium in every sense of the
> word. Unless you sample it directly - drill a hole and
> dig stuff out of it - one does not know much. While any of
> the proposed models might be defended in one setting, the
> reality is that there are gazillion other situations in the
> same survey where the model is invalid.

Okay, thank you for your post, Rune.

Nicholas

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