Difference between revisions of "Geopsy: H/V and Spectrum Toolboxes: Time Tab"

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== Use ==
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= '''Use''' =
  
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This toolbox tab contains the parameters to select the part of the signal used for [[H/V_spectral_ratio|H/V]] or [[Spectral_amplitudes|Spectrum]] processing on which window selection is performed.
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[[Image:HV_SPEC_toolb_time.png|thumb|right|300px|''Time'' tab of the H/V and Spectrum toolboxes]]
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The two series of paramaters are described in two areas:
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The toolbox '''Time''' tab is used to customize the parameters for selecting the signal windows used for processing.
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Two series of parameters are described in two sections:
  
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* the global time range area
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* the global time range section
  
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* the time windows area
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* the time windows section
  
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A third area gives information on the number of selected windows obtained after applying to the signal the parameters of the two precedent areas.
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A third section gives information on the number of selected windows obtained after applying the parameters defined in the two precedent sections.
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At the very bottom two buttons indicate wether to [[Geopsy: Load_Toolbox_Parameters|load parameters]] from previouly processed data or to [[Geopsy: Load_Toolbox_Parameters|start signal processing]] signal processing.
 
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[[Image:HV_SPEC_toolb_time.png|thumb|center|400px|''Time'' tab of the H/V and Spectrum toolboxes]]
 
 
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== Global time range area ==
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= '''Global time range section''' =
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Select the portion of the signal that will be processed ([[Geopsy: Time_Limits|more informations]]).
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[[Image:HV_SPEC_toolb_time_global.png|thumb|right|300px|''Global time range'' section in the ''Time'' tab of he H/V and Spectrum toolboxes]]Used to select the portion of the signal that will be processed ([[Geopsy: Time_Limits|more informations]]).
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[[Image:HV_SPEC_toolb_time_global.png|thumb|right|300px|''Global time range'' area in the ''Time'' tab of he H/V and Spectrum tollboxes]]
 
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== Time windows area ==
 
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Short-duration disturbances of the signal can be avoided during [[H/V_spectral_ratio|H/V]] or [[Spectral_amplitudes|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 satrt of an earthquake. Here an anti-trigger algorithm is used, which is exactly the opposite: it detects transients but it tries to avoid them. For more information on this topic it it suggested to consult the SESAME user guidelines <ref>Guidelines for the implementation of the H/V spectral ratio technique on ambient vibrations measurements, processing and interpretation, [http://SESAME-FP5.obs.ujf-grenoble.fr], 62 pages, April 2005</ref>. Windows are then processed indidualy to get individual window H/V or Spectrum, which are then averaged.
 
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This area comprises four sub-tabs:
 
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* general
 
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* raw signal
 
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* filter
 
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* filtered signal
 
  
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=== General sub-tab ===
 
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This sub-tab contains the parameters used to select stable signal windows.
 
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[[Image: HV_SPEC_toolb_time_time_gen.png|thumb|right|300px|''General'' sub-tab in the ''Time windows'' area of the ''Time'' tab ]]
 
 
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==== Window length ====
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= '''Time windows section''' =
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There are three ways to define window length (duration, in seconds) [[Image: HV_SPEC_toolb_time_time_general_popup.png|''Window length'' pop-up menu]]
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[[Image:HV_SPEC_toolb_time_windows.png|thumb|right|300px|''Time windows'' section in the ''Time'' tab of the toolboxes]]
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<br style="clear: both"/>
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Short-duration disturbances of the signal can be avoided during [[H/V_spectral_ratio|H/V]] or [[Spectral_amplitudes|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 <ref>Guidelines for the implementation of the H/V spectral ratio technique on ambient vibrations measurements, processing and interpretation, [http://SESAME-FP5.obs.ujf-grenoble.fr], 62 pages, April 2005</ref>. Windows are then processed individually to get H/V or Spectrum curves in all selected windows, which are then averaged
  
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* exactly: all selected windows will have the same exact duration. Only one value needs to be entered.
 
  
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[[Image: Time-time_exactly.png|300px]]
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'''MAIN ARTICLE''': [[Geopsy: H/V and Spectrum Toolboxes: Time Tab: Time windows|Time windows]]
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* at least: selected windows will have a duration comprised between two values.
 
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[[Image: Time-time_atleast.png|300px]]
 
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This may be useful in case of very perturbated signal to get the most possible windows.
 
 
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==== Window Overlaping ====
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= '''Number of windows section''' =
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[[Image: View stations all.png|thumb|'right|300px|''Number of windows'' section]]In the '''Number of windows'' section, underneath the [[Geopsy: H/V and Spectrum Toolboxes: Time Tab: Time windows|Time windows]] tabs, a pop-up menu and a numerical display are used to show the number of selected windows.
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* When the ''Overlap'' box is not checked
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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.
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[[Image: Time-time_nooverlap_menu.png|300px|Overlap box (not checked)]]
 
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contiguous selected signal windows will not overlap, resulting in this type of windowing
 
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[[Image: Time-time_nooverlap.png|300px|Overlap box (not checked)]]
 
 
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* When the ''Overlap'' box is checked
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[[Image: View station pop-up.png|thumb|right|300px|Pop-up menu of the ''Number of windows'' section]]
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[[Image: Time-time_overlap_menu.png|300px|Overlap box (checked)]]
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The number of windows selected in each station of a multiple processing may be displayed individually.
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contiguous selected signal windows will overlap by a chosen percentage, resulting in this type of windowing
 
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[[Image: Time-time_overlap.png|300px|Windows with overlap box checked)]]
 
 
<br style="clear: both"/>
 
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==== Bad Sample Definition and Use ====
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[[Image: View station 1 Station.png|thumb|right|300px|Number of windows of the selected station]]
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[[Image: Time-time_Bad_sample.png|300px]]
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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.
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* It is possible to define a level above which a sample is considered as bad, i.e. that should rejected when defining stable windows.
 
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To do so, check the ''Bad sample threshold'' box and enter the desired threshold, which is a percentage of the maximum amplitude over the entire signal.
 
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* A maximum number of bad samples may be accepted inside windows during the selection process.
 
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Check the Bad sample tolerance button and enter the number of tolerated bad samples.
 
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This option may only be used when the previous one is checked.
 
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[[Image: Time-time_Bad_sample.png|300px]]
 
 
<br style="clear: both"/>
 
<br style="clear: both"/>
  
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==== Anti-triggering choice ====
 
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The goal of the anti-triggering is to keep the most stationary parts of ambient vibrations, and to avoid the transients. Eventualy, user's defined bad sample are also considered as part of the non-stationary signal.
 
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Two types of anti-trigger may be applied to he signal, both based on [[Geopsy: STA/LTA|STA/LTA]] detection.
 
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''Italic text''
 
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[[Image: Time-time_antitriggering.png|300px]]
 
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* Anti-trigger on raw signal
 
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When the ''Anti-triggering on raw signal'' box is checked, the anti-trigger is applied sample per sample all along the entire signal, using the STA/LTA parameters entered in the ''Raw signal'' sub-tab.
 
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* Anti-trigger on filtered signal
 
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When the ''Anti-triggering on filtered signal'' box is checked, the signal is first filtered using the parameters entered in the ''Filter'' sub-tab, and then the anti-trigger is applied sample per sample all along the entire signal, using the STA/LTA parameters entered in the ''Filtered signal'' sub-tab.
 
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IMPORTANT NOTICE: when using the anti-triggering on the filtered signal, the signal is filtered ONLY to select stable windows.
 
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The processing is then performed on the RAW signal.
 
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In order to process filtered signal the raw signal should first be filtered with the [[Geopsy: Filter|''Filter'']] in the [[Geopsy: Waveform_Menu|''Waveform'']] menu.
 
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=== Raw Signal sub-tab ===
 
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This sub-tab is divided into two areas.
 
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[[Image: HV_SPEC_toolb_time_time_raw.png|300px]]
 
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* STA/LTA parameters area (to the left), includes STA length, LTA length, as well as minimum and maximum STA/LTA thresholds.
 
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* ''Apply to'' area (to the right), indicates to which tracks the anti-trigger is applied (top, above the  … : Vertical, North, East) and to which file (bottom underneath the … : "Strong Peak").
 
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Simply check the boxes of the tracks and files that are to be processed.
 
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=== Filter sub-tab ===
 
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[[Image: HV_SPEC_toolb_time_time_filter.png|300px]]
 
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[[Geopsy: Filter|''Filter'']]
 
  
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== References ==
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= References =
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<referenes/>
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<references/>

Latest revision as of 14:23, 28 February 2013

Use

Time tab of the H/V and Spectrum toolboxes

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

Global time range section in the Time tab of he H/V and Spectrum toolboxes

Used to select the portion of the signal that will be processed (more informations).


Time windows section

Time windows section in the Time tab of the toolboxes

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

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.


Pop-up menu of the Number of windows section

The number of windows selected in each station of a multiple processing may be displayed individually.

Number of windows of the selected station

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.


References

  1. ↑ Guidelines for the implementation of the H/V spectral ratio technique on ambient vibrations measurements, processing and interpretation, [1], 62 pages, April 2005
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