Which component in a 3-component Sp receiver function is the actual Sp RF?

Question

In a 3-component Sp RF I have the green's function in P,SV, and SH. The actual component to the RF that shows the Sp conversion (the one always published in the literature), which would represent as a negative phase around the LAB and a big positive one over the Moho, would have to be the P component...right? I have three components to these RFs, but they were never labeled, two of them have the zero lag arrival at the same exact time while the third has its zero lag arrival occur about 3 seconds before the other two. Remember this is an Sp RF!

As an S wave in an non-isotropic (i.e. Earth) media would have some level of energy in two components, SV and SH (albeit the SH is always a lower SNR given the Earth is not actually isotropic), it completely makes sense that the two components in the receiver function that happen to have the zero lag direct arrival of the wave at the EXACT same time would have to be the SV and SH components.

Given that one of these two has a much lower SNR I could also argue which one is SV and which one is SH. Furthermore, since the only remaining component has its direct arrival occur BEFORE the other two I should naturally conclude this to be the P component! ....but this is where it gets complicated....this supposed P component does not have a clear positive spike where the Moho should be and a clear negative spike where the LAB should be.....the supposed SV component does....

I feel like I am just standing at the door before I walk in and learn an incredibly powerful lesson about the Earth, but I also feel like I want someone to walk through with me and tell me I'm on the right track in terms of my thinking....so am I??

Answer 1

I am not sure I clearly understand the question, but here is a quote from the paper that I looked at a while ago about S Receiver Functions.

From: Yuan, Xiaohui, Rainer Kind, Xueqing Li, and Rongjiang Wang. " The S Receiver Functions: Synthetics and Data Example ." Geophysical Journal International 165.2 (May, 2006): 555-564:

"Here we briefly summarize the processing steps for generating S receiver functions. The ZNE-component seismograms of S and SKS waves are rotated firstly into the ZRT system with the back azimuth determined by locations of the receiver and earthquake. The ZRT components are further ro-tated into the P-SV-SH system with the incidence angle determined by minimizing the amplitudes at time of S/SKS arrival on the P component. Waveforms are visually selected to avoid the confusing of S and SKS phases. Data with strong interference of S and SKS are excluded. A window of S/SKS waves on the SV component is deconvolved from the P component for source equalization. For direct comparison with the P receiver functions, we need to reverse the time axis as well as the amplitudes of the S receiver functions.Move-out correction is then applied for all the PRFs, SRFs and SKSRFs, with a reference slowness of 6.4 s deg−1 and the IASP91 model as reference."

Does this help?