15 Oct
2016
15 Oct
'16
12:01 a.m.
Awesome! Thanks Thomas!
On Fri, Oct 14, 2016 at 1:50 PM, Thomas Lecocq <Thomas.Lecocq(a)seismology.be>
wrote:
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:
--
Ashton F. Flinders, Ph.D
U.S. Geological Survey
345 Middlefield Road
Menlo Park, CA 94025
(650) 329-5050
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(a)vaw.baug.ethz.ch
MSNoise mailing list
MSNoise(a)mailman-as.oma.be
http://mailman-as.oma.be/mailman/listinfo/msnoise
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(a)usgs.gov>ov>:
> 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(a)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(a)usgs.gov>ov>:
> >>> 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(a)mailman-as.oma.be
>>> http://mailman-as.oma.be/mailman/listinfo/msnoise
>> >>
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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(a)mailman-as.oma.be
> http://mailman-as.oma.be/mailman/listinfo/msnoise
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