[CIG-SEISMO] SW4 prefilter in SRF file (Aaron Moya)

[Petersson, Anders]

Hi Aaron,
In order to correctly use the prefilter option together with the rupture command, the srf file must be constructed with sufficiently large offsets in the time functions that are included in the srf file.

Because the source time function is filtered, there will be no significant frequency content in the numerical solution that exceeds the corner frequency in the filter. By choosing a grid size that gives at least 8 grid points per shortest wave length the computed solution will not contain any unresolved features. Thus, there is no need for any additional (spatial) filtering of the image files or any additional (temporal) filtering of the sac files. 

When estimating the max frequency, use fmax = 3*fc, where fc is the corner frequency.

Anders

On 9/17/18, 12:09 PM, "CIG-SEISMO on behalf of cig-seismo-request at geodynamics.org" <cig-seismo-bounces at geodynamics.org on behalf of cig-seismo-request at geodynamics.org> wrote:

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       1. SW4 prefilter in SRF file (Aaron Moya)
    
    
    ----------------------------------------------------------------------
    
    Message: 1
    Date: Sun, 16 Sep 2018 14:33:50 -0500
    From: Aaron Moya <aaronmoya at gmail.com>
    To: cig-seismo at geodynamics.org
    Subject: [CIG-SEISMO] SW4 prefilter in SRF file
    Message-ID:
    	<CADM3Ta68mt+4wNnWrF8eLNowAer48eMc_LiaQEmiOEiHSPd=xg at mail.gmail.com>
    Content-Type: text/plain; charset="UTF-8"
    
    Hello:
    
    In SW4 the prefilter option is used to remove unresolved motions. I
    understand it can be used to create movies. In order to use it, the
    source term must have the "t0" option set to a large enough value in
    order to avoid unphysical oscillations due to an abrupt start.
    
    In case of not using  a single source but a SRF file with the rupture
    option, how does the "prefilter" option work? There is no "t0" option.
    What happens to the images obtained from the image command? Are they
    also filtered?
    
    -- 
    Aarón
    
    
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