[MSNoise] Autocorrelations in MSNoise

[Aurélien Mordret]

Hi Thomas,

What is the pre-processing of the noise when computing autocorrelations? Is
it the same as for the cross-correlations?

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.

-- 
==========================

Postdoctoral fellow
Department of Earth, Atmospheric and Planetary Sciences
Massachusetts Institute of Technology
54-526
Cambridge, MA  02139-4307
e-mail: mordret at mit.edu
web: http://web.mit.edu/mordret/www