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

[Tom Eulenfeld]

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!
> 
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