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Hi Marc,
I want to ask you if it is possible to save the result of an H / V curve obtained with the directional energy that can be used for the calculation of the power spectrum and which represents the curves of the single components that lead to that spectral ratio. In my attempts, for example saving the H / V result of a 30 ° rotation of the horizontal components (with directional energy option) and loading the relative log file for the calculation of the power spectrum, I realized that it is identical to the one of the spectral ratio obtained with squared energy. I also tried to rotate the components with the rotate components option in the Waveform section and then calculate H / V with the squared energy, but the result is different from the one using the directional energy option.
Is there something wrong with my request?
I am attaching a plot with 4 well-differentiated spectral ratio curves, which correspond to four log files that provide the same power spectrum.
Thanks
Luigi

Hi Luigi,

I can't see what's wrong. On your plot, we can see a progression from N/V to E/V with the intermediate steps 30 an 60 deg. I also checked on a test case: the square average output is different for the 30 deg. directional output.

If you rotate the components by 30 deg. with the waveform tool, you can get the N to coincide with the direction 30 deg. . The square average is building a H made of the average of the rotated N but also the rotated E component. In the directional option, only the rotated component is included. That's probably the reason for the observed difference. If the component N and E are similar (equipartition of the noise wavefield), rotation has almost no effect and the square average option is almost equal to the directional energy option.

Best regards,

Marc

Thanks Marc.

I need 2 more clarifications, please:

1) when geopsy calculates H / V spectrum does it use the rotation of the components (like the one in Waveform-rotate components) ?
2) how can I extract the spectra of the two components for each rotation? My idea would be to rotate the components (with waveform/rotate) to the desired angle, calculate the power spectrum and then save the .spec files of the horizontal components. Is this right?

In some tests I have done it has never happened to me that the H / V ratio changes with the rotation of the components, especially for the frequency of the peak. Does this seem like a shareable statement to you, or was I not lucky ?

Best Reagards
Luigi

when geopsy calculates H / V spectrum does it use the rotation of the components (like the one in Waveform-rotate components) ?

In waveform rotate components, the three components are rotated with a rotation matrix in the three axes. For H/V rotate, spectrum rotate, and directional energy, geopsy only computes the projection of N and E on the desired direction.

how can I extract the spectra of the two components for each rotation? My idea would be to rotate the components (with waveform/rotate) to the desired angle, calculate the power spectrum and then save the .spec files of the horizontal components. Is this right?

If you run a spectrum rotate, you get the spectrum in all directions from 0 to 180 deg. . Two components over 90 deg. is the same as one component over 180 deg. What you propose should return the same results but it is manual and longer to achieve. It could be checked for one or two angles (e.g. 30 and 60). Just look at the spectrum of the N component for instance.

Ok, Marc, thanks, but if I want to represent the N and E components for different projections (or rotations) how can I do it practically without calculating the power spectra? It seems to me that this was also the question posed by Giuseppe and this is your answer:

".......
In the result file, there is one spectrum per direction from 0 to 180 deg. (excluded), with a default step of 10 deg. (adjustable in the parameters). If you want the rotated NS and EW, let's say rotated by 20 deg., You can run
CODE: SELECT ALL
awk '{if ($ 2 == 20) print $ 1, $ 3}' CN01_Z.spec> NS_20.spec
awk '{if ($ 2 == 100) print $ 1, $ 3}' CN01_Z.spec> EW_20.spec
If you want the rotated signals, you can use rotate from Waveform menu. It is also accessible from the command line via the waveform console. "

Basically this is what interests me too, but with Windows how can I get the same result if not following the long path (rotate components and calculate the power spectra saving the .spec)?

Best regards
Luigi

You can open the spec file in a spreadsheet and extract the portions you want. Effectively, 'awk' is not available in GeopsyLand. You can try MobaXterm, MSys, git bash,... there are terminal emulations under Windows. There is also an agreement between Microsoft and Ubuntu to get a bash terminal under Windows.

Sorry, with "spec" do you means the spectrum results (Z.spec, N.spec, E.spec)?
If so, the spec files contain frequency, average and Standard deviation, but not rotations.
So how do I extract the portion of interest, for example N20?
I'm probably not well tuned ....
Sorry
Luigi