Re: [MSNoise] Autocorrelations in MSNoise

Hi Thomas, As far as I understand you haven't changed anything since then in the code concerning the pre-processing when computing autocorrelations. Right? Greetings from Athens, Christos From: Thomas Lecocq <thomas.lecocq@... <http://gmane.org/get-address.php?address=thomas.lecocq%2d7ewb5K7nbqnl%2fIpH24cmtA%40public.gmane.orgSubject: Re: Autocorrelations in MSNoise <http://news.gmane.org/find-root.php?message_id=54DB931F.5080705%40seismology.beNewsgroups: gmane.science.geophysics.msnoise <http://news.gmane.org/gmane.science.geophysics.msnoiseDate: 2015-02-11 17:36:31 GMT (1 year, 14 weeks, 6 days, 11 hours and 16 minutes ago) Hello Aurélien, Le 11/02/2015 18:30, Aurélien Mordret a écrit : > Hi Thomas, > What is the pre-processing of the noise when computing autocorrelations? Is > it the same as for the cross-correlations? Yeah, currently it's the same, WHICH IS NOT GOOD ! (that's why it's written somewhere NOT TO USE AUTOCORR), but that might not be trivial to find... Your suggestion makes absolutely sense ! Are you used to github etc ? If yes, please fork and PR an updated version of whiten ! (including a autocorr=False flag in the def, maybe?)! Regards from Brussels Thomas > If yes, would it be better to not fully whiten the data before > autocorrelation as the only information comes from the amplitude spectrum > (and not the phase)? > I suggest to modify a bit the whiten.py function to keep the structure of > the whole code similar. Following Gorbatov et al. (2013), instead of > putting the amplitude spectrum =1 (with tapper) I would use a normalisation > with a water-level in the form > A(freq) = A(freq)/max(A(freq),c*max(A(freq))) > With A the amplitude spectrum and c the water-level factor (which is > typically on the order of 1%). > It should not change the results for the cross-correlations and improve the > autocorrelations. > Does it make sense or did I missed something? > Cheers, > Aurelien > REF: > Gorbatov, A., Saygin, E., & Kennett, B. L. N. (2013). Crustal properties > from seismic station autocorrelograms. *Geophysical Journal International*, > **192**(2), 861-870.