Bug in ZRT Receiver Function Calculation

[santisoler]

Applying a RF calculation using the ZRT coordinate system gives wrong result.

For example, the following code computes the RF for a ZRT rotation on the first set of the example stream loaded with rf_read():

from rf import read_rf, rfstats

stream = read_rf()
stream = stream[:3]
rfstats(stream)

stream.detrend()

stream.filter("bandpass", freqmin=0.01, freqmax=1)

stream.rf(rotate="NE->RT", method='P')
stream.select(component="R").plot(type='relative',
                                  reftime=stream[0].stats.onset)

We expect something like what Ammon (1991) shows in this Figure:

But instead, we get the following RF in the radial direction:

[trichter]

Thank you for reporting this bug!

rf uses the rotate method from ObsPy. (this convention)
Because the Q component in the LQT system points towards the source, the receiver function must be multiplied by -1 to get the correct result. This "correction" is wrongly applied for the R component in the ZRT system. The peak therefore becomes negative.

I am unsure about the T component. I assume that the multiplication with -1 is not correct, too.

[trichter]

This should be solved now. I published a new version on PyPi.

[trichter]

By the way you can use

stream.select(component="R").plot_rf()

to plot the receiver functions aligned with the onset.

[santisoler]

Thanks @trichter !