Polarization

Users Mailing List Archive
1

Dear Obspy users;

I have a problem trying to use the polarization algorithm from obspy. When I run polarization.eigval, I get an error:

Traceback (most recent call last):
  File "./pol.py", line 44, in <module>
    main()
  File "./pol.py", line 31, in main
    pol = polarization.eigval(trz,trn,tre,fk,1)
  File "/Applications/ObsPy.app/Contents/MacOS/lib/python2.7/site-packages/obspy/signal/polarization.py", line 57, in eigval
    leigenv1 = np.zeros(datax.shape[0], dtype='float64')
AttributeError: 'Trace' object has no attribute 'shape'

I am reading a three component sac file and the error says that the object (the trace) have no shape attribute, a numpy data attribute. How do I fix this problem, what do I have to do to the data in order to give it a shape attribute ?

I am adding the piece of code I am trying to execute.

pol.py (1.04 KB)

2

Hi Javier,

eigval expects the data as input not traces. The line in your code should be

pol = polarization.eigval(trz.data,trn.data,tre.data,fk,1)

Hope it helps,
Tom

3

Hi Javier,

you need to pass numpy arrays instead of obspy.core.Trace objects to the eigenvalue function.

Changing
  pol = polarization.eigval(trz,trn,tre,fk,1)
to
  pol = polarization.eigval(trz.data,trn.data,tre.data,fk,1)

Should do the trick. Take care of the component orientation!

Cheers!

Lion

4

Dear users;

I am using the polarization function from the signal package of Obspy
I get the eigen values, rectiliniarity and planarity.

What I need is azimuth and incoming angle. For such functions I need the eigen functions. Is there a way of getting the eigen functions from polarization.eigval ?
Does any body has an example of how to get azimuth and incoming angle from polarization.eigval

Thank you in advance for your help

Javier Fco. Pacheco

5

Dear Javier

by accident I needed the same functionality.
You can use function "polar" from
https://github.com/trichter/sito/blob/master/rf.py and adapt it to
your needs. At the moment it computes azimuth and incidence angle
averaging over the input data. Please test if it works as you expect.

Cheers, Tom

6

Dear all,

I'm just testing an extended version of the polarization modul in obspy:
this will include Flinn's method as well as a modified version of Vidale
(1986) (adapted window selection) as well as a simple computation of the
particle motion vector. The output will be azimuth/incidense and various
linearity values. You can check out using:

https://github.com/jwassermann/obspy/blob/3C-analysis/obspy/signal/polarization.py

It still needs some polishing (so it needs a few more days) but seems to
work in most cases.

Cheers Jo

7

Thanks a lot Tom

Regards;

Javier Fco. Pacheco

8

Great !

I use the new polarization.py and works fine, but I could not find out how do you get an array out of the function:

pol = vidaleAdapt(stream, noise_thres, fs, flow, fhigh, spoint, stime, etime)

I had to change the output of vidaleAdapt to get an np array. But I would like to know how to get from the variable pol, an array I can plot, say the azimuth or the rectiliniarity

Thank you for your help;

Javier Fco. Pacheco

9

Hi Javier,

you call the different methods via the module polarizationAnalysis. I
attach a python script which gets the traces (in your case prop. reading
form file), prepares the rest and does the plotting - hope that works
for you....

seishub-3C-analysis.py (4.88 KB)

10

Hi all,

if anybody could at some point make a short example (also usable as a
test case) for the ObsPy Tutorial (as basic as possible, probably using
the example data using read()) with a plot at the end -- that would be
great!

Also, these new routines are not yet merged into master, so they might
still change a bit.. Have a look at the corresponding pull request to
stay up to date: https://github.com/obspy/obspy/pull/505

best,
Tobias