[Qopen] for local earthquakes (less then 70 km)

[Petr Predein]

Sorry to bother you again, but now I'm running Qopen with different
settings.
And it seems that such parameters as velocities, mean density or use_picks
parameter (whether I have P- and S-onset or it’s calculated), will not
change the result dramatically. But, I noticed, setting of coda_window
length, is another matter.

With setting by default,
"coda_window": ["S+20s", ["S+150s", "3SNR"]]
that means window will start 20 second after time of S-wave, with length =
130s (or while more then 3*SNR)? and will start just after "bulk_window" =
["S-2s", "S+20s"]

But  if I want coda_window to be no more then 40 second, for example, with
"bulk_window" = ["S-0.2s", "S+5s"],
if I set coda_window: ["S+5s", ["S+45s", "3SNR"]]
With this setting I get g0 values (and finally Q scattering) with
absolutely different order, then with first one.
Is it correct, config format and results? It's hard for me to conclude.
And to see time where directly coda will start and end, I searched output
files, and didn’t succeed.
I attach config file with my settings, just in case.


ср, 15 янв. 2020 г. в 22:48, Petr Predein <crmpeter at gmail.com>:

> Thank you so much for detailed answer and very useful instruction with
> examples. I really appreciate it! I also find Qopen package works for me
> and hope the result will not put me to shame. Thanks!
>
> ср, 15 янв. 2020 г., 17:10 Tom Eulenfeld <tom.eulenfeld at uni-jena.de>:
>
>> Hello Petr,
>>
>> please use "[Qopen]" keyword in the subject when posting a message to
>> the mailing list. Then, it its categorized correctly and automatically
>> accepted.
>>
>> The choice of Sens-Schönfelder and Wegler (2006) is comprehensive in
>> their setting. Still, it is IMHO absolutely no problem to use shorter
>> distances. I have done it myself. Your dataset appears suitable. Please
>> take the following in mind:
>>
>> 1. v0 can be set to another velocity, it should be a "mean" value for
>> the used model, also time windows need to be adapted.
>> 2. The resulting Q-values for scattering and intrinsic attenuation will
>> be "mean" values over the sampled volume. This means Q-values will
>> depend on the scale of the dataset and used time windows.
>> 3. For local datasets with small earthquakes, results for low
>> frequencies will not be useful.
>>
>> Setting the time windows in your config is a bit of trial and error. The
>> direct S wave window should cover the the complete S wave train, and the
>> coda window best starts at the end of the S wave window.
>>
>> For your convenience, I append the config files I used for the USArray
>> (Eulenfeld and Wegler, 2017) and the config files for the different
>> regions investigated in Eulenfeld and Wegler (2016).
>>
>> Even for a successful inversion, have a look at the log file and watch
>> out for errors.
>>
>> I hope you will find the package and these hints useful.
>> Best regards!
>>
>> Tom
>>
>>
>>
>>
>> On 15.01.20 03:51, Petr Predein wrote:
>> > Hello, I am new to this mailing list, and very interesting in using
>> > Qopen package for calculating intrinsic and scattering attenuation.
>> > And my question to respected community is, can I use earthquakes with
>> > epicenter very close to some station, with magnitudes no more then
>> > 3-3.5, for example.
>> > Normally, I read in (Sens-Schönfelder C., Wegler U., 2006: Radiative
>> > transfer theory for estimation of the seismic moment, p. 3)
>> > that hypocentral distance should be greater than 60 km, because it is
>> > inappropriate to use mean velocity of S-waves about 3.5 km/s for
>> shorter
>> > distances (upper layers of the Earth crust?)
>> > But it is also shown that Qopen uses improved method, unlike original
>> > (Sens-Schönfelder C., Wegler U., 2006).
>> > Also, I understand that it's incorrect one cannot use earthquakes with
>> > epi distances less then several km up to 10 km, depending on frequency
>> > range.
>> > Finally, can I use Qopen for small earthquakes with epicentral distance
>> > from 10 to 70 km? (average depth is in range 15-20 km, hovewer).
>> > And, if yes, which setting should I use in conf.json file to avoid big
>> > errors, with stations on free surface.
>> > Thanks in advance!
>> >
>>
>
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <https://lserv.uni-jena.de/pipermail/seistools/attachments/20200116/7cd7da61/attachment-0001.html>
-------------- next part --------------
A non-text attachment was scrubbed...
Name: conf_BR.json
Type: application/json
Size: 4196 bytes
Desc: not available
URL: <https://lserv.uni-jena.de/pipermail/seistools/attachments/20200116/7cd7da61/attachment-0001.json>