[CIG-SEISMO] Prefilter (Aaron Moya)

[Petersson, Anders]

Dear Aaron,
You correctly interpreted the warning message. The 2-pass filter is
acausal and the precursor tail is quite long for such low frequencies.
Anders 

On 11/3/15, 12:00 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. Prefilter (Aaron Moya)
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>----------------------------------------------------------------------
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>Message: 1
>Date: Tue, 3 Nov 2015 09:46:12 -0600
>From: Aaron Moya <aaronmoya at gmail.com>
>To: cig-seismo at geodynamics.org
>Subject: [CIG-SEISMO] Prefilter
>Message-ID:
>	<CADM3Ta4DqO_6dJyCVB4b0utP7hfr_hrHCANeOsapFpoiiWTR4Q at mail.gmail.com>
>Content-Type: text/plain; charset="utf-8"
>
>When using the following simulation parameters.
>
>fo = 0.5
>fmax = 2.5* fo = 1.25
>freq = 2*pi*fo = 3.14159
>
>then
>
>t0 in the source term of SW4 should be
>
>t0 >= 6/freq = 1.91
>
>
>time t=17
>source lat=9.956 lon=-84.268 topodepth=12.0e3 m0=5.01e15 type=GaussianInt
>freq=3.14159 t0=2.0  strike=S_TR dip=D_IP rake=R_AK
>prefilter fc1=0.1 fc2=0.5
>
>
>When I use the "prefilter" command with the default values
>(type=butterworth, passes=2) for fc1=0.1 and fc2=0.5, I get the following
>message,
>
>
>Filter precursor = 3.311652e+01
>
>*** WARNING: the 2 pass prefilter has an estimated precursor of length
>3.311652e+01 s
>*** To avoid artifacts due to sudden startup, increase t0 in all source
>commands by at least 3.302638e+01
>margin = 4.850902e-02
>
>Does this mean that "t0" in the source term should be a little larger than
>33,1 s instead of 1.91?
>
>I appreciate your answer,
>
>Aaron
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