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Hi Marc, some months ago I posted this question about m and nppm parameters. I think this is a topic of interest for which it would be important for you to give an answer (at least for me). The ellipticity was calculated with HV TFA and plotted with max2curve of Geopsy version 2.

"Hi Marc,
I would like to submit this topic to help me in the conscious choice of the parameters m and nppm for the calculation of the right ellipticity curve.
In Deliverable D4 of the Neries-jra4 project we read in the conclusions:
"The best parameter selection for the Morlet wavelet parameter m is in the range of 4-16 with preference given to m = 8. For the number of selected wavelets per minute, nppm, we recommend using the range 5 or lower, with preference to lower values ​​as low as 1 when the recording time is sufficiently large to obtain good statistics. It is also advisable to process the data with different values ​​of nppm to identify the stable parts of the fundamental mode ellipticity curve ".
In the case that I submit to you I would like to know if the choice made is correct or not. In the first image I have the H/V curve and those of ellipticity with different values ​​of m and nppm = 10 (the time series have a duration of 1h). In the second I plotted the curve with m = 2 (which I considered the best) with 4 nppm values, from 3 to 20.
On the basis of the results I have identified that nppm = 5 is the curve to be used for the joint inversion (curve with singularity).
What is your opinion on this?"

Thanks
Luigi

Hi Luigi,

Sorry to have left your message for too long unanswered.
I agree that among the proposed values the combination m=2 and nppm set to 3 or 5 is probably closer to reality than the others. I prefer the approach proposed by Hobiger et al. (2009 in GRL). HVTFA with low nppm, just use a very small part of the signal. It looks for the very strong pure Rayleigh wave. On the contrary Raydec proposed by Manuel Hobiger uses the full signal length and stacks. To improve the reliability, I would check also with this method, soon inside geopsy but one year ago it was already coming soon. Without any support I can send you a copy of the Matlab code for Raydec.

Best regards,

Marc

Thanks, Marc.

When in Geopsy? Never?
"Not scientist" users like me (who I am not familiar with Matlab), how can they proceed to the joint inversion if they do not have the possibility to obtain a reliable ellipticity curve from the H / V curve?
Only from HRBF or radial and transverse Capon when, however, the minimum frequency is that of the frequency of the H / V peak .... or by applying the reduction of the amplitude of the right flank of the peak by a factor equal to the square root of 2. HVTFA gives a better or similar quality result?
Or is the problem not so crucial to the final outcome?

I remember finding very interesting and attractive the paper for the study of the seismic hazard in Lucerne, where the CVT was applied.
The use of Rayleigh-wave ellipticity for site-specific hazard assessment and microzonation: application to the city of Lucerne, Switzerland
Valerio Poggi, Donat Fah, Jan Burjanek and Domenico Giardini

A question without response: would the results have been different by applying Raydec?

Best regards
Luigi