Abnormal ESAC Record

[ESBornand]

Dear all, I made an ESAC record in the shape of a rectangle with 24 geophones with a sample of 2 ms and 20 min duration, when processing it, the spectral density of each geophone showed that 23 of the geophones have an amplitude much less than a geophone, I appreciate your comments, LINK to download and fix the rectangle is attached, THANKS!

https://drive.google.com/file/d/1yu2-fB ... share_link

[admin]

Hi,

Your sensors are placed at inter-distances that do not exceed 17 m, hence we expect similar spectral densities at intermediate and low frequencies. Looking at the spectral densities only, three sensors have distinct responses below 1 Hz: R022, R005 and R006. Also, R002 and R013 do not behave like the others above 1 Hz. All the others are similar below 6 Hz. Above, some minor differences can be noted. The varying locations may explain these details. I do not have the coordinates of the sensors directly ready so I did not try any array processing. I suspect disturbances in array processing using those sensors. You can try to process with and without those sensors (one or several). Do you note any difference?

If you can redo the experiment, it would be nice to place the sensor at the same locations, note the serial numbers of the sensors. Record and analyse directly the results. Note the strange responses. Swap dubious sensors with "normal" response sensors. Is the weird response attached to the sensor or is it linked to a particular location?

Best regards,

Marc

[ESBornand]

Thanks for your prompt response Marc, in the previous post I attached the coordinates of the rectangular array in JPG, when processing you will realize that Geophone R022 has amplitudes far above the rest, if R022 is the problem, in GEOPSY how can it be done? delete that channel and be left with only 23 geophones?
Thanks!

[admin]

Open the signals in a table, select only the signals you want to process and drag them to a new graphic window (drag them on the graphic icon in the toolbar).

[luigiV]

Hi Marc, first of all happy new year.

I have a question:
In the title of the topic there is the term ESAC that you have not covered in the answer. I remember asking you in the past if Geopsy could process data with the Esac code. I've never received a reply, but I don't think it can. Can you confirm that?

Thanks
Luigi

[admin]

Hi Luigi,

Thanks to your message, I took a bit of time to check how to implement ESAC in the SPAC toolbox with minimal modifications. ESAC (Ohori paper) is highly cited and I have always been curious to compare it to MSPAC (Bettig et al) but without finding the appropriate opportunity. In fact, I took the whole day to implement it (short question but not so short answer!). It is now running for the next release. The output is also a .target file but with directly the dispersion curves for vertical, radial and transverse. I'm currently testing it on synthetic signals.

Best regards,

Marc

[luigiV]

Hi Marc,
very good news!
As an old man, I worry about having time to use this tool and the new release...

Best Regards
Luigi