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<div class="moz-cite-prefix">Hi Kasper:<br>
<br>
It's possible, but I still would recommend low passing the
seismograms to bring them within the numerical validity range. If
you are doing a similation in a finite domain, e.g., a box with
three absorbing boundaries and a free surface, then, yes, you also
need to use a low frequency cut off to account for this. Thus a
bandpass is the best option.<br>
<br>
Best regards,<br>
<br>
Jeroen<br>
<br>
<br>
<br>
On 4/16/13 5:27 PM, Kasper VanWijk wrote:<br>
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<div dir="ltr">Kia Ora Jeroen!
<div><br>
</div>
<div style="">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?</div>
<div style=""><br>
</div>
<div style="">Also, are you aware of limitations on the LOW
frequency information in the data with the Dirac source, or
should those be well represented?</div>
<div style=""><br>
</div>
<div style="">groet,</div>
<div style="">kasper</div>
<div style=""><br>
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<div class="gmail_extra"><br>
<br>
<div class="gmail_quote">On Tue, Apr 16, 2013 at 4:18 AM, Jeroen
Tromp <span dir="ltr"><<a moz-do-not-send="true"
href="mailto:jtromp@princeton.edu" target="_blank">jtromp@princeton.edu</a>></span>
wrote:<br>
<blockquote class="gmail_quote" style="margin:0 0 0
.8ex;border-left:1px #ccc solid;padding-left:1ex">Dear
Martin:<br>
<br>
Yes, you can. The way to do this is to calculate the imuplse
response,<br>
i.e., the Green's function, and subsequently convolve with
whatever you<br>
choose to be your source-time function in postprocessing.
Note that you<br>
will still have to bandpass the result to bring it within
the numerical<br>
validity range, i.e., make sure you are resolving all the
frequencies of<br>
interest with your mesh.<br>
<br>
Best regards,<br>
<br>
Jeroen<br>
<div class="im HOEnZb"><br>
<br>
On 4/11/13 11:30 AM, Martin Martin wrote:<br>
> Dear SPECFEM2D Team,<br>
><br>
> I would like to know if it is possible to create my
own source function<br>
> - I mean other than using the five time function
which is provided :<br>
> Rickett, gauss, heaviside, etc ?<br>
><br>
> Thank you<br>
><br>
> Best wishes,<br>
><br>
> Martin<br>
><br>
<br>
</div>
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