Selecting windows to analyze transient signals

This forum is dedicated to discuss all problems and suggestions related to the use of geopsy database and its plugins (array processing, H/V,...).
lucapuzzilli
Posts: 5
Joined: Wed Mar 09, 2011 1:29 pm
Location: Roma

Selecting windows to analyze transient signals

Postby lucapuzzilli » Wed Jun 13, 2012 2:12 pm

Hello dr. Wathelet, in the HV plugin of course we can remove transiente signals using the anti-triggering option: some authors said that including transient in the H/V spectral ratio should notworsen the estimation of the fundamental resonance frequency of a site.
So after the selection of some time windows of "good" signal, i try to analyze also the transient signals.
For example in a registration of N minute i've found some discarded period with anti-triggering option, then with the option to "inverse" windows selection i obtained a few windows in wich there was "high energy transient": the plugin allows me to obtain the HV for these windows.
Is this correct and you've never tried before to do the same?
Regards
Luca

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Re: Selecting windows to analyze transient signals

Postby admin » Mon Jul 02, 2012 12:12 pm

I agree that the transient signal might contain valid information about the soil structure. What you should avoid is sources located very close to the station. The distance is related to the wavelength. i.e. variable according to the considered frequency. For short distance waves, the partition between vertical and horizontal is mostly influenced by the type of source and not really by the medium properties. If your measurements is not located right on the side of a passing road, or if no one is walking at a few meters of the station, transients are certainly strong energy coming from distant sources which has sufficient distance to develop surface waves or body wave resonance, i.e. leading to a reliable and stable H/V curve.

Your test has been carried out several times during SESAME project. It is case dependent. Personally, I use the anti-trigger only in some rare case.


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