[obspy-users] Rotate function

Florian Fuchs florian.fuchs at univie.ac.at
Thu Jan 11 16:17:08 CET 2018


Dear all,

I am struggling with the rotate function of ObsPy.

I have a Stream with 3 Traces - one for each channel. The channels are 
labeleld HHZ, HH2 and HH3:

3 Trace(s) in Stream:
Z3.A333A.00.HH2 | 2017-12-12T07:46:39.165000Z - 
2017-12-12T07:46:41.155000Z | 100.0 Hz, 200 samples
Z3.A333A.00.HH3 | 2017-12-12T07:46:39.165000Z - 
2017-12-12T07:46:41.155000Z | 100.0 Hz, 200 samples
Z3.A333A.00.HHZ | 2017-12-12T07:46:39.165000Z - 
2017-12-12T07:46:41.155000Z | 100.0 Hz, 200 samples

Channels are 2+3 instead of N+E because the sensor is not pointing to 
the North. Now I want to rotate this Stream such that I actually do get 
ZNE data. I have the inventory file with the correct orientation 
specified. Still, I cannot get my data rotated.

If I use only

stream.rotate(method='->ZNE', inventory=inv)
or
stream._rotate_to_zne(inv)

it doesn't do anything. No error message either. Certainly the data is 
not rotated. I figured I should indicate the components, since my 
channels are not Z12 or 123. So I tried specifying the components:

First of all I now wonder if the order of the channels matter and if 
they relate to the order of Traces in the Stream? Anyways, whatever 
order I chose, I end up with an error message:

stream.rotate(method='->ZNE', inventory=inv, components='Z23')
or
stream._rotate_to_zne(inv, components='23Z')

-> IndexError: list index out of range

The error occurs in this part of the function code:
# to be used in rotation
   3294         st = self.select(network=network, station=station, 
location=location)
-> 3295         st = (st.select(channel=channels[0]) + 
st.select(channel=channels[1]) +
   3296               st.select(channel=channels[2]))
   3297         # remove the original unrotated traces from the stream

This makes me wonder if there is maybe a bug in the function and that 
rearranging the Traces doesn't work correctly? Or do I mess it up by 
not setting the right channel order?

Any help is much appreciated.

Thank you very much,
Florian
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