[CIG-SEISMO] Source Time function

[Kasper VanWijk]

Kia Ora Jeroen!

Greetings from Auckland. I noticed your advice to Martin about source time
functions. As you know, I am mostly an experimental guy, so forgive me if I
ask a trivial question, but I am working with a student on extending Aki's
SPAC method. It involves the summation of many sources. When we use the
Dirac option in SPECFEM2D (i.e. simulate the Green function response), we
get what you told Martin: good signals in the range that the mesh supports.
We have noticed, however, that the high-frequency numerical noise seems to
stack out. Is it well known that this high-f noise is (apparently)
uncorrelated? Or are our eyes deceiving us?

Also, are you aware of limitations on the LOW frequency information in the
data with the Dirac source,  or should those be  well represented?

groet,
kasper




On Tue, Apr 16, 2013 at 4:18 AM, Jeroen Tromp <jtromp at princeton.edu> wrote:

> Dear Martin:
>
> Yes, you can. The way to do this is to calculate the imuplse response,
> i.e., the Green's function, and subsequently convolve with whatever you
> choose to be your source-time function in postprocessing. Note that you
> will still have to bandpass the result to bring it within the numerical
> validity range, i.e., make sure you are resolving all the frequencies of
> interest with your mesh.
>
> Best regards,
>
> Jeroen
>
>
> On 4/11/13 11:30 AM, Martin Martin wrote:
> > Dear SPECFEM2D Team,
> >
> > I would like to know if it is possible to create my own source function
> > - I mean other than using the five time function which is provided :
> > Rickett, gauss, heaviside, etc ?
> >
> > Thank you
> >
> > Best wishes,
> >
> > Martin
> >
>
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