Difference between revisions of "Active source experiment (MASW)"
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=== General overview === | === General overview === | ||
| − | First introduced by Al-Husseini et al. (1981), Mari (1984), | + | First introduced by Al-Husseini et al. (1981), Mari (1984), Gabriels et al. (1987), the Multichannel analysis of surface waves was popularized by Park et al. (1999). This technique relies on the recording along a 1D linear profile of seismic signals produced by a controlled source (hammer, vibrator, explosion, etc.) and analysis of surface wave dispersion properties after applying slant-stack or FK transform to the recorded seismic section. In the following tutorial, only the [[FK|FK]] transform is used. |
=== Getting ready === | === Getting ready === | ||
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| + | ===Description of the MASW toolbox === | ||
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| + | [[Image:MASW_ToolBox_Overview.png|thumb|right|400px|Overview of Masw toolbox]] | ||
| + | Open the MASW toolbox by pushing the following plugin icon [[Image:MASWToolboxPluginIcon.png|30px]] or, alternatively, by selecting ''Linear F-K for active experiments'' in [[Geopsy: Tools|''Tools'']] menu. | ||
| + | Two windows should then open as displayed in the figure on the right: the ''Linear FK toolbox'' to set up processing parameters and a ''Linear fk results'' to display MASW results. The ''Linear FK toolbox'' is composed of four tabs: | ||
| + | * ''Pre-processing'' tab is used to define the time window, the tapering, the amplitude normalization, etc. | ||
| + | * ''Processing'' tab allows to define the processing scheme (FK or HRFK) | ||
| + | * ''Output'' tab is used to set up the frequency and slowness band to be processed and the output filename | ||
| + | * ''Time'' tab allows to select the time limits and part of the signals to be processed and the time window length; | ||
| + | * ''Curves'' tab is used to save, remove or load dispersion curves that are picked | ||
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* HRFK (cross-link avec HRFK de Mathias) | * HRFK (cross-link avec HRFK de Mathias) | ||
* normalize energy | * normalize energy | ||
Revision as of 15:31, 11 March 2010
General overview
First introduced by Al-Husseini et al. (1981), Mari (1984), Gabriels et al. (1987), the Multichannel analysis of surface waves was popularized by Park et al. (1999). This technique relies on the recording along a 1D linear profile of seismic signals produced by a controlled source (hammer, vibrator, explosion, etc.) and analysis of surface wave dispersion properties after applying slant-stack or FK transform to the recorded seismic section. In the following tutorial, only the FK transform is used.
Getting ready
- Download the compressed signal file.
- Launch Geopsy and set Rxxx as name in the Geopsy Loading Preferences.
- Load and view these downloaded signals. A seismic section as the one displayed in the figure on the right should then appeared.
- Check in the Table signal viewer that sensors location is ranging from 0 to 92 meters with a 4 meters spacing.
- Check that source location is X=-4 meters by editing Set sources in Geopsy Edit menu. Alternatively, you can also add the Source X field in the Table signal viewer.
Description of the MASW toolbox
Open the MASW toolbox by pushing the following plugin icon 
or, alternatively, by selecting Linear F-K for active experiments in Tools menu.
Two windows should then open as displayed in the figure on the right: the Linear FK toolbox to set up processing parameters and a Linear fk results to display MASW results. The Linear FK toolbox is composed of four tabs:
- Pre-processing tab is used to define the time window, the tapering, the amplitude normalization, etc.
- Processing tab allows to define the processing scheme (FK or HRFK)
- Output tab is used to set up the frequency and slowness band to be processed and the output filename
- Time tab allows to select the time limits and part of the signals to be processed and the time window length;
- Curves tab is used to save, remove or load dispersion curves that are picked
- HRFK (cross-link avec HRFK de Mathias)
- normalize energy
FK Computing
- computation for one single file and picking of the curve
- alternatives : 1) create a stack file and then compute the FK; 2)compute FK for all shots and then stack the FK maps
