[MSNoise] One more clarification

Fri Oct 14 20:50:01 UTC 2016

Hi all,

so, as explained:

default['analysis_duration'] = ["Duration of the Analysis (total in seconds : 3600, [86400])",'86400']
default['corr_duration'] = ["Data windows to correlate (in seconds) [1800.]",'1800.']
default['overlap'] = ["Amount of overlap between data windows [0:1[ [0.]",'0.0']

analysis_duration should not be changed. It's there because I originally 
planned to allow support for other job bases, not only the "1day job" 
(e.g. for acoustic kHz data). But to date, it's not implemented. 
corr_duration is the window length, in the loaded day, that is 
cross-correlated, and they step by the overlap. The "chunking" is not 
for efficiency, it's for quality rebuilding of the CCF. In the simplest 
case of a big event in the middle of your 2 daily seismic traces, you'll 
have the CCF of those full traces will look like an autocorrelation, but 
if you slice the day in chunks, only one of the, for example 48 slices, 
will be autocorr, and thus the daily stack of those windows will be less 
affected by this event. So, msnoise computes N CCFS per day and stacks 
them to a daily CCF (default is linear stack = average). Thomas
On 13/10/2016 18:14, Flinders, Ashton wrote:
> Ok, thanks Lukas!
>
> I brought up a similar question last week about how the cross-correlation
> segmenting was done and after talking to Esteban/Thomas my impression was
> that corr_duration simply split the time segments into chunks, and did the
> cross correlation in chunks PURELY for efficiency reasons, and then rebuilt
> the total daily time cross correlation afterwards, and did not stack them.
> But this seems to not be true then?
>
>
> -ashton
>
> On Thu, Oct 13, 2016 at 3:09 AM, Lukas Preiswerk <preiswerk at vaw.baug.ethz.ch
>> wrote:
>> Ashton,
>>
>>> I think the part that is throwing me off a bit is the "Daily NCFs were
>> then
>>> obtained by stacking 30-min NCFs".
>>> This sound like to be, they took their individual 30 min NCFs and stacked
>>> them, so that each day is represented by the stacked summation of 48
>>> independent NCFs.
>> Agreed. If you set corr_duration to 1800 and leave analysis_duration
>> in the standard 86400, this is exactly what you get in the 1-Day
>> stacks.
>>
>>> I assumed that meant that both corr_duration and analysis duration were
>> set
>>> to 3600, but maybe not.
>> As I mentioned, if you set analysis_duration to 3600,
>> then you only use 1 hour of data each day and leave the rest
>> untouched… Try it for yourself with the keep_all option enabled and by
>> looking at the data in the h5 files.
>>
>> Lukas
>>
>>
>>
>>
>> 2016-10-12 18:08 GMT+02:00 Flinders, Ashton <aflinders at usgs.gov>:
>>> Thanks Lukas!
>>>
>>> I think the part that is throwing me off a bit is the "Daily NCFs were
>> then
>>> obtained by stacking 30-min NCFs".
>>>
>>> This sound like to be, they took their individual 30 min NCFs and stacked
>>> them, so that each day is represented by the stacked summation of 48
>>> independent NCFs.
>>>
>>> I assumed that meant that both corr_duration and analysis duration were
>> set
>>> to 3600, but maybe not.
>>>
>>> I'll probably just send an email out to them to see what parameters they
>>> used.
>>>
>>>
>>> On Tue, Oct 11, 2016 at 11:35 PM, Lukas Preiswerk <
>>> preiswerk at vaw.baug.ethz.ch> wrote:
>>>
>>>> Hi Ashton,
>>>>
>>>> I can partly answer 1) and 3). First, corr_duration would be 30*60 in
>>>> their paper (corr_duration is in seconds). As far as I understand,
>>>> analysis_duration should almost always be 86400. Setting the
>>>> analysis_duration
>>>> smaller could be used to prevent loading a full day of data for
>>>> specific cases, like super high frequency data (8kHz or more). The
>>>> remaining processing still works on days and not multiples of
>>>> analysis_duration. For examplem if you set analysis_duration to 3600,
>>>> then you only use 1 hour of data each day…
>>>>
>>>> Hope that helps!
>>>>
>>>> Lukas
>>>>
>>>>
>>>> 2016-10-11 18:57 GMT+02:00 Flinders, Ashton <aflinders at usgs.gov>:
>>>>> Hi all, I was just reading through Taka'aki and Forents new paper
>> using
>>>>> MSNoise, and was hoping just for a wee bit more clarification on the
>>>>> MSnoise processing scheme (wasnt quite clear in the docs).
>>>>>
>>>>>
>>>>> The paper says;
>>>>> "We first removed the instrument response from 1-day-long waveform to
>>>>> obtain ground motion in displacement. Daily displacement data were
>>>>> bandpassed between 0.08 and 2.0 Hz, down-sampled into 10  Hz, and
>> split
>>>>> into 30-min-long data. Those 30-min-long data were spectral whitened
>> in a
>>>>> frequency range of 0.1–0.9  Hz and then one-bit normalized. With those
>>>>> one-bit normalized data, the NCFs were computed for all possible
>>>>> combinations of components. Daily NCFs were then obtained by stacking
>>>>> 30-min NCFs."
>>>>>
>>>>>
>>>>> Q1) So just in terms of implementation in msnoise admin, the
>> 30-min-long
>>>>> duration would be controlled by "analysis_duration" correct?
>>>>>
>>>>> Q2) If you remove the instrument response, is it always removed from
>> a 1
>>>>> day chunk, or is it removed from a chunk equal in size to
>>>>> "analysis_duration"? (the docs say 1 day, but I wasnt sure if this was
>>>> just
>>>>> referencing the default "analysis_duration" time).
>>>>>
>>>>> Q3) This probably isnt the intended usage, but if you used
>>>>> "analysis_duration" longer than a day, would you expect things to
>> behave?
>>>>> Thanks as always!
>>>>>
>>>>> -ashton
>>>>>
>>>>>
>>>>> p.s. paper;
>>>>> http://earth-planets-space.springeropen.com/articles/10.
>>>> 1186/s40623-016-0538-6
>>>>> --
>>>>> Ashton F. Flinders, Ph.D
>>>>> U.S. Geological Survey
>>>>> 345 Middlefield Road
>>>>> Menlo Park, CA 94025
>>>>> (650) 329-5050
>>>>> _______________________________________________
>>>>> MSNoise mailing list
>>>>> MSNoise at mailman-as.oma.be
>>>>> http://mailman-as.oma.be/mailman/listinfo/msnoise
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>>>> MSNoise mailing list
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>>>>
>>>
>>>
>>> --
>>> Ashton F. Flinders, Ph.D
>>> U.S. Geological Survey
>>> 345 Middlefield Road
>>> Menlo Park, CA 94025
>>> (650) 329-5050
>>> _______________________________________________
>>> MSNoise mailing list
>>> MSNoise at mailman-as.oma.be
>>> http://mailman-as.oma.be/mailman/listinfo/msnoise
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