Geopsy: H/V and Spectrum Toolboxes: Time Tab
Contents
Use
The toolbox Time tab is used to customize the parameters for selecting the signal windows used for processing. Two series of parameters are described in two sections:
- the global time range section
- the time windows section
A third section gives information on the number of selected windows obtained after applying the parameters defined in the two precedent sections.
Global time range section
Used to select the portion of the signal that will be processed (more informations).
Time windows section
Short-duration disturbances of the signal can be avoided during H/V or Spectrum processing by using an anti-trigger window selection to remove the transients. The objective is to keep the most stationary parts of ambient vibrations, and to avoid the transients often associated with specific sources (footsteps, close traffic). This objective is exactly the opposite of the usual goal of seismologists who want to detect signals, and have developed specific trigger algorithm to track the unusual transients possibly indicating the start of an earthquake. Here an anti-trigger algorithm is used, which is exactly the opposite: it detects transients and tries to avoid them. For more information on this topic, it it suggested to consult the SESAME user guidelines [1]. Windows are then processed individually to get H/V or Spectrum curves in all selected windows, which are then averaged
MAIN ARTICLE: Time windows
Number of windows section
In the 'Number of windows section, underneath the Time windows tabs, a pop-up menu and a numerical display are used to show the number of selected windows.
When all stations is displayed in the pop-up menu, the number of windows in the numerical display is the total number of windows selected over all the stations. It is also displayed when a single station is processed.
The number of windows selected in each station of a multiple processing may be displayed individually.
The number of windows of the selected station appears in the numerical display, and simultaneously a zoom of the selected station appears in the signal Graphic Sheet.
