[SAC-HELP] Transfer problem

Philip Crotwell crotwell at seis.sc.edu
Fri Feb 21 10:50:38 PST 2014 

I guess an edit is the easiest. Reporting it to the ET network operators so
it can be fixed permanently might be nice as well.

Guessing an appropriate reference frequency is tough. The SIS conf call had
a discussion about autopicking a freq for an overall gain a while back, and
I think the consensus was that the overall gain should probably be
calculated at the sensor, stage 1, frequency unless that was >= the nyquist
of the channel, and then to use nyquist/2. That is probably not a bad
heuristic, but you can still probably get into trouble if you get out of
the flat part of the pass band. Not easy to do automatically i suspect.

Philip



On Fri, Feb 21, 2014 at 10:33 AM, Robert Casey <rob at iris.washington.edu>wrote:

>
> Thanks for the helpful reply, Philip.  I had Mary Templeton looking at it
> and she came the same conclusion as you.  She made a plot to illustrate:
>
>
>
>
> So the recommendation, I take it, is for the frequency of sensitivity,
> Blockette 58, stage 0, field 5 to be changed to 1.00000E+00.
>
> What I noticed was that the Normalization frequency of stage 1 is in fact
> set to 1 Hz, so I wonder if this is a product of merging the sensor to a
> datalogger response and then not seeing a trickle-down alteration of the
> frequency of sensitivity to stage 0?  The PDCC tool doesn't handle this,
> for example, but I do recall having discussions about this and seeing the
> solution as ambiguous.
>
> So if Blaine edits the RESP file, is that the way to proceed?
>
> -Rob
>
>
>
> Hi
>
> Responses are at best confusing, but you need to remember that the gain is
> not just a value, it is a value at a particular frequency.
>
> The last stage (stage zero) is supposed to be the overall gain and should
> be the product of the gains at each stage, but only if the frequency of
> each stage is the same. In this case the stage zero gain is +1.25829E+09,
> but it is given at freq of 5e-2. The stage 1 gain is 1.5e3, but at a freq
> of 1Hz. So to be proper, you must adjust the gain based on the poles and
> zeros from 1Hz to 5e-2 Hz before you multiply. Looking at the response plot
> here:
>
>
> http://service.iris.edu/irisws/evalresp/1/query?net=ET&sta=CPCT&loc=00&cha=HHZ&time=2009-06-07T00:00:00&units=def&annotate=true&output=plot
>
> it looks like 5e-2 is just barely beyond the flat part of the response,
> which explains why evalresp says that the stage 1 gain is  1.369329E+03
> instead of 1.5e3. It has rolled off just a bit at 5e-2 Hz compared to 1Hz
> which is in the flat part of the response.
>
> To be honest, I think that the mistake in this response is not in the gain
> numbers, but rather in the frequency reported in the stage zero. It
> probably should have the frequency in the stage zero as 1Hz instead of
> 5e-3Hz . So, likely in this case the 1.25829E+09 is the gain you want to
> use even though evalresp complains.
>
> Hope this helps,
> Philip
>
>
>
> On Thu, Feb 20, 2014 at 1:44 PM, Brian Savage <savage at uri.edu> wrote:
>
>> Dear Blaine,
>>
>> This error is generated by evalresp.  You should be able to confirm this
>> by running evalresp on your RESP file.
>>
>> For example
>> % evalresp CPCT HHE 2010 001 0.001 20 -v -f RESP.ET.CPCT.HHE.2
>> << EVALRESP RESPONSE OUTPUT V3.3.3 >>
>>  WARNING (norm_resp): computed and reported sensitivities differ by more
>> than 5 percent.
>>  Execution continuing.
>>  --------------------------------------------------
>>   RESP.ET.CPCT.HHE.2
>>  --------------------------------------------------
>>   ET CPCT 00 HHE  2009,001,00:00:00 2011,026,00:00:00
>>    Seed units: Velocity(in)->Counts(out)
>>    computed sens=1.14868E+09 (reported=1.25829E+09) @ 5.00000E-02 Hz
>>    calc_del=8.92261E-01  corr_app=8.92261E-01  est_delay=8.92261E-01
>>  final_sint=0.01(sec/sample)
>>       stage  1: LAPLACE     A0=6.259322E+08 NZeros=  2 NPoles=  5
>> Sd=1.369329E+03
>>       stage  2: GAIN        Sd=1.000000E+00
>>       stage  3: FIR_SYM_1   H0=1.000000E+00 Ncoeff=  1
>> SamInt=1.953125E-06 Sd=8.388610E+05
>>       stage  4: FIR_SYM_2   H0=1.000000E+00 Ncoeff= 36
>> SamInt=1.953125E-06 Sd=1.000000E+00
>>       stage  5: FIR_SYM_2   H0=1.000000E+00 Ncoeff=  6
>> SamInt=1.562500E-05 Sd=1.000000E+00
>>       stage  6: FIR_SYM_1   H0=1.000000E+00 Ncoeff=  7
>> SamInt=3.125000E-05 Sd=1.000000E+00
>>       stage  7: FIR_SYM_2   H0=1.000000E+00 Ncoeff= 48
>> SamInt=6.250000E-05 Sd=1.000000E+00
>>       stage  8: FIR_SYM_2   H0=1.000000E+00 Ncoeff=126
>> SamInt=2.500000E-04 Sd=1.000000E+00
>>       stage  9: FIR_SYM_1   H0=1.000000E+00 Ncoeff=501
>> SamInt=5.000000E-04 Sd=1.000000E+00
>>       stage 10: FIR_SYM_1   H0=1.000000E+00 Ncoeff=501
>> SamInt=1.000000E-03 Sd=1.000000E+00
>>       stage 11: FIR_SYM_1   H0=1.000000E+00 Ncoeff=501
>> SamInt=2.000000E-03 Sd=1.000000E+00
>> --------------------------------------------------
>> %
>>
>> Possibly someone at IRIS can comment on this further.  I think the first
>> gain value is being modified due to a Analog PoleZero.
>>
>> Brian
>> savage at uri.edu
>>
>> On Feb 18, 2014, at 4:57 PM, Blaine Bockholt (bbckholt) wrote:
>>
>> I am attempting to remove the instrument response of some data.  I
>> downloaded the RESPFILE from IRIS and while using the evalresp option of
>> transfer, I get the following error:
>>
>> "WARNING (norm_resp): computed and reported sensitivities[ET.CPCT.00.HHE]
>> differ by more than 5 percent."
>>
>> I thought the final sensitivity at the end of the file is the product of
>> all the different gain/sensitivities of each stage.  When I calculate it by
>> hand, I get the sensitivity reported.  I am not sure where this error is
>> coming from, nor I am sure how SAC calculates the sensitivity.  Thanks.
>>
>> Blaine
>>
>> Here is the command I use
>>
>> trans from evalresp fname ET.CPCT.resp to none freqlim 0.001 0.002 15 20
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>>
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