Active source experiment (MASW) - Revision history

Marc at 13:11, 20 December 2011

2011-12-20T13:11:39Z

Marc: /* = Manual picking */

2011-12-20T13:10:26Z

= Manual picking

Marc: /* Manual picking */

2011-12-20T13:10:12Z

Manual picking

Marc: /* Picking a dispersion curve */

2011-12-20T13:08:56Z

Picking a dispersion curve

Marc: /* Parameters setting */

2011-12-20T11:24:53Z

Parameters setting

Marc: /* Parameters setting */

2011-12-20T11:24:27Z

Parameters setting

Marc: /* Getting ready */

2011-12-20T11:13:09Z

Getting ready

Marc: /* Getting ready */

2011-12-17T14:02:14Z

Getting ready

Marc at 13:05, 12 March 2010

2010-03-12T13:05:56Z

Marc at 13:05, 12 March 2010

2010-03-12T13:05:15Z

@@ Line 1: / Line 1: @@
 [[Category:Tutorials]]
-=== General overview ===
+== 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|FK]] transform is used.
-=== Getting ready ===
+== Getting ready ==
 [[Image:MASW_DISPLAY_SEISMIC_SECTION_NEW_NEW.png|thumb|right|400px|Exemple of a seismic section.]]
@@ Line 18: / Line 18: @@
 <br style="clear: both"/>
-=== Description of the MASW toolbox ===
+== Description of the MASW toolbox ==
 [[Image:MASW_ToolBox_Overview_new.png|thumb|right|400px|Overview of Masw toolbox]]
@@ Line 31: / Line 31: @@
 <br style="clear: both"/>
-=== Parameters setting ===
+== Parameters setting ==
 [[Image:MASW_Parameters_PREPROCESSING.png|thumb|right|250px]]
@@ Line 57: / Line 57: @@
 <br style="clear: both"/>
-=== Picking a dispersion curve ===
+== Picking a dispersion curve ==
 [[Image:Masw_dispersion_curve_plot.png|thumb|right|400px|Dispersion curve plot with a clear bi-modal propagation corresponding to shot gather displayed above.]]
@@ Line 66: / Line 66: @@
 === Manual picking ===
-== Semi-automatic picking ==
+=== Semi-automatic picking ===
-== Fully automatic picking ==
+=== Fully automatic picking ===

@@ Line 64: / Line 64: @@
 All picked curves are available under tab ''Curves'' from the toolbox with a [[SciFigs: Curve Browser|curve browser]].
-==== Manual picking ===
+=== Manual picking ===
 == Semi-automatic picking ==
 == Fully automatic picking ==

@@ Line 64: / Line 64: @@
 All picked curves are available under tab ''Curves'' from the toolbox with a [[SciFigs: Curve Browser|curve browser]].
-== Manual picking ==
+==== Manual picking ===
 == Semi-automatic picking ==
 == Fully automatic picking ==

← Older revision		Revision as of 13:08, 20 December 2011
Line 58:		Line 58:

	=== Picking a dispersion curve ===		=== Picking a dispersion curve ===
		+
		+	[[Image:Masw_dispersion_curve_plot.png\|thumb\|right\|400px\|Dispersion curve plot with a clear bi-modal propagation corresponding to shot gather displayed above.]]
		+
		+	In the result window, one plot is created for each identified shot. A right click inside a plot lets you switch to picking mode (''Pick''). Leave this mode by clicking again on menu item ''Pick''.
		+	All picked curves are available under tab ''Curves'' from the toolbox with a [[SciFigs: Curve Browser\|curve browser]].
		+
		+	== Manual picking ==
		+
		+	== Semi-automatic picking ==
		+
		+	== Fully automatic picking ==

@@ Line 54: / Line 54: @@
 * Specify the phase slowness band to be processed. Note that you can also specify the phase velocities. However computation will be performed in the slowness domain.
 * There are three options to normalize the beampower results: no normalization, normalization by the power spectra, normalization for each frequency by the maximum of the beampower.
 === Picking a dispersion curve ===

← Older revision		Revision as of 11:24, 20 December 2011
Line 54:		Line 54:
	* Specify the phase slowness band to be processed. Note that you can also specify the phase velocities. However computation will be performed in the slowness domain.		* Specify the phase slowness band to be processed. Note that you can also specify the phase velocities. However computation will be performed in the slowness domain.
	* There are three options to normalize the beampower results: no normalization, normalization by the power spectra, normalization for each frequency by the maximum of the beampower.		* There are three options to normalize the beampower results: no normalization, normalization by the power spectra, normalization for each frequency by the maximum of the beampower.
		+
		+	=== Picking a dispersion curve ===

@@ Line 12: / Line 12: @@
 * [[Loading and viewing signals|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 [[Geopsy:_Table| 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|Geopsy Edit]] menu. Alternatively, you can also add the ''Source X'' field in the [[Geopsy:_Table|Table signal viewer]].
+* Check that source location is X=-4 meters by editing sources with ''Set sources'' in [[Geopsy:_Edit_menu|Geopsy Edit]] menu. Alternatively, you can also add the ''Source X'' field in a [[Geopsy:_Table|Table signal viewer]], unlock editing in [[Geopsy:_Edit_menu|Geopsy Edit]] menu,  and edit manually the table fields. Another way is to run ''Set Header'' in [[Geopsy:_Edit_menu|Geopsy Edit]] menu with ''SourceX=-4''.
 <br style="clear: both"/>

@@ Line 8: / Line 8: @@
 [[Image:MASW_DISPLAY_SEISMIC_SECTION_NEW_NEW.png|thumb|right|400px|Exemple of a seismic section.]]
-* Download the [[Media:exemple_masw.seg2|compressed signal file]].
+* Download the [[Media:Exemple_masw.tar.gz|compressed signal file]].
 * Launch [[Geopsy|Geopsy]] and set ''Rxxx'' as name in the [[Geopsy:_Preferences| Geopsy Loading Preferences]].
 * [[Loading and viewing signals|Load and view]] these downloaded signals. A seismic section as the one displayed in the figure on the right should then appeared.

@@ Line 43: / Line 43: @@
 * Specify the [[Geopsy: Time Limits|time limits]] of the window length which will be used for FK processing: all samples out of the time window defined previously inthe ''Pre-processing'' tab will be set to 0.
 * Specify the [[Geopsy: Sampling Frequency|Frequency band width]] to be used in the computation of [[FK|beampower]] spectra
-* When checking the ''High Resolution'' box, one can also compute [[HFRK|HRFK]] instead of [[FK|FK]]. In such a case however, one has to specify a [[HRFK|damping factor]] in order to stabilize the cross spectral matrix before inverting it. The optimum damping value is found by trial and error.
+* When checking the ''High Resolution'' box, one can also compute [[HRFK]] instead of [[FK]]. In such a case however, one has to specify a [[HRFK|damping factor]] in order to stabilize the cross spectral matrix before inverting it. The optimum damping value is found by trial and error.
 <br style="clear: both"/>

@@ Line 33: / Line 33: @@
 [[Image:MASW_Parameters_PREPROCESSING.png|thumb|right|250px]]
 In ''Pre-processing'' tab:
-* Select the minimum and maximum source-to-receiver distance which will be processed. This allows to exclude signals close to the source shot (this distance should be at least one wavelength in order to reduce [[Geopsy:Active_source_experiment_(MASW)|near-field effects)]] or at large distances for which the signal-to-noise ratio may be low.
+* Select the minimum and maximum source-to-receiver distance which will be processed. This allows to exclude signals close to the source shot (this distance should be at least one wavelength in order to reduce near-field effects or at large distances for which the signal-to-noise ratio may be low.
 * Select the begin and end time window that will be considered during the processing. A [[Geopsy:_Taper|taper]] is then applied to the selected time window.
 * Specify the [[Geopsy:_Time_Limits|time limits]] to be processed. A [[Geopsy:_Taper|taper]] is then applied to the selected time interval.
@@ Line 41: / Line 41: @@
 In ''Processing'' tab:
-* Specify the [[Geopsy:_Time_Limits|time limits]] of the window length which will be used for FK processing: all samples out of the time window defined previously inthe ''Pre-processing'' tab will be set to 0.
+* Specify the [[Geopsy: Time Limits|time limits]] of the window length which will be used for FK processing: all samples out of the time window defined previously inthe ''Pre-processing'' tab will be set to 0.
-* Specify the [[Geopsy:_Sampling_Frequency|Frequency band width]] to be used in the computation of [[FK|beampower]] spectra
+* Specify the [[Geopsy: Sampling Frequency|Frequency band width]] to be used in the computation of [[FK|beampower]] spectra
 * When checking the ''High Resolution'' box, one can also compute [[HFRK|HRFK]] instead of [[FK|FK]]. In such a case however, one has to specify a [[HRFK|damping factor]] in order to stabilize the cross spectral matrix before inverting it. The optimum damping value is found by trial and error.
@@ Line 49: / Line 49: @@
 [[Image:MASW_Parameters_OUTPUT.png|thumb|left|250px]]
 In ''Output'' tab:
-* Specify the [[Geopsy:_Sampling_Frequency|frequency band]] to be processed.
+* Specify the [[Geopsy: Sampling Frequency|frequency band]] to be processed.
 * Specify the phase slowness band to be processed. Note that you can also specify the phase velocities. However computation will be performed in the slowness domain.
 * There are three options to normalize the beampower results: no normalization, normalization by the power spectra, normalization for each frequency by the maximum of the beampower.