geopsy.org

Hello.
I have velocity time histories of 10 shots for 24 geophones from MASW testing. How to generate a dispersion curve in Geopsy by stacking the 10 shots?

Hi,

There two ways to achieve the stack: in time domain with a simple summation of all shots and in frequency domain by summing the FK spectra. The latter is preferred because you can avoid synchronisation errors. Triggers are never perfect and there are always tiny errors. In the result sheet of MASW tool, select all the plots (one per shot) you want to stack, go to menu "Tools/Stack selected plots". An additional plot is created with the stack.

Best regards,

Marc

Thanks Marc.
However, when I am generating dispersion images, the dispersion images from 2 different shots are coming in 2 different windows and they are not getting stacked together. How to get multiple dispersion images in a single window so that we can stack them? I have a separate notepad file for every single velocity time history from every single shot.

Aniket

You can put the signals recorded for several shot in a single graphical window by dragging and dropping them. Start the Active FK tool for the graphic viewer containing all shots. You will have several dispersion plots in the result sheet. Once they are in the same sheet, you can select them together and stack them.

Best regards,

Marc

Hi Marc,
I want to ask you what are the steps to obtain a sum file in time domain. I tried, but the result is always a graphical window with all files to be stacked in sequence, just like with dragging and dropping.
Thanks
Luigi

I assume that you want to stack various records of active shots. For each shot you have to create a Group. View the signals of the first shot and go to menu "Waveform/Add signals", select the group to add. The current viewer and the selectable groups must have the same number of signals. It is probably more correct is the sampling frequency and the sample number are the same but it is not checked.

There is also a tools called "Noire reduction" which provide stack of signals, phase correction of signals and a smart weighted stack. I'm unsure if this tool still work for recent releases.

Sorry Marc,
but in my release (3.4.2) under Waveform there is no "add signals" option (only substract signals).