[CIG-SEISMO] Asking SPECFEM2D

[Carl Tape]

Dear Jungrak,

At one time, I experimented with the 2 x 2 moment tensor source in
SPECFEM2D. If you set the source type to moment tensor, then you can
specify Mxx = 1, Mzz = 1, Mxz = 0, and this will give you an isotropic
source. You can change these elements to vary the amount of isotropic
component in the source. So going from an isotropic source to a double
couple, you will see the S waves disappear (in simple models).

Make sure to view snapshots of the wavefield to make sure it is doing the
things you want expect.

Carl

---------------------------------------------------------------
Carl Tape
Assistant Professor
Geophysical Institute
University of Alaska Fairbanks
Phone: 907-474-5456
Email: carltape at gi.alaska.edu
Web: http://www.giseis.alaska.edu/input/carl/
---------------------------------------------------------------


On Sat, Jan 25, 2014 at 1:19 PM, Jungrak SON <jrson2011 at gmail.com> wrote:

> Before asking a question, I appreciate to whom may have made great effort
> to develop this valuable tool and let students can use it.
>
> Hi, I am a MS student and fortunately I have been doing an interesting
> research by using SPECFEM2D. I hope to be able to submit my research
> abstract to many conferences in this Fall to show off great SPECFEM tool. :)
>
> Let me ask you a simple question. In class, I learned that there are
> several kinds of land seismic sources such as *weight drop, dynamite,
> vibroseis*. *How can I distinguish the weight drop and dynamite source in
> my modeling?*
>
> I am afraid that dynamite, an explosive pressure to everywhere, is
> different from my SOURCE setting (source_type = 1 #elastic forces,
> anglesource = 0).
>
> Do I have to use "momentum tensor sources"?  I read that this has N*m
> unit, but I don't know what the difference is. *Could you explain more
> about "momentum tensor sources"?*
>
> Thanks for your time and considering.
>
> Sincerely,
>
>
> - JungRak Son
> MS student at Texas A&M Univerisy
>
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