H/V Rotate

Introduction

Result of a H/V Rotate computing, displaying the H/V as a function of azimuth

This tool is used to obtain the H/V in the horizontal plane, i.e., as a function of azimuth, from any type of 3D vibration signals (ambient vibrations, earthquake…). The example used for explanations is an ambient vibration recording on soil.

Here, a series of H/V is calculated from 0° to 180° every 10 °, and is presented in a frequency-azimuth graphic. This graphic can be used to analyse the H/V in the horizontal plane. Results are displayed between 0° and 180°, the 180-360° being a symetry of the 0-180°.

For H/V processing, the data should have:

• 3 signals: North-South, East-West and Vertical;
• a common name (see here to modify the name of the component);
• enought common samples in time to be processed.

As for the other tools, the data can be processed:

• from a graphic viewer, to verify the windowing and to display the results;
• from a table. In this case, Geopsy will display only the resulting curves.

A global description of the Spectrum rotate Toolbox is available for more details.

This tool is very similar to the HV Toolbox in its use.

There are only two differences between this tool and the HV tool:

• there is no automatic possibility to save a file with the HV curves,
• the computing of the Fourier amplitude spectra implies synchronous windows.

Getting ready

• Download compressed signal file. If the file has been already downloaded (as for H/V or Spectrum purposes for example), do not download it again.
• Load and view these downloaded signals.
• Select H/V Rotate in menu Tools (alternative ways to start a tool)

Window selection

General sub-tab in Time tab of toolbox

This part is devoted to define how the windowing will be performed (see also Time windows section for more details):

- automatic selection with an anti-trigger algorithm (STA/LTA) or not ?

- are bad samples accepted (and how many) ?

- may windows overlap or not, and if yes by how much ?

-...

• Make sure you are in the Time Tab, and that parameters are as in the example window. The Anti-triggering on raw signal button has been checked.
• To make sure that parameters are set up alright, it is possible to download the compressed parameter file and load toolbox parameters.

Raw signal sub-tab in Time tab of toolbox with the anti-trigger parameters

• Click on the Raw signal, to check that anti-trigger parameters are as in the example window.

Select pop-up menu

• Click on the Select button and select Auto into the pop-up menu.

Number of selected windows

• The number of selected windows appears at the bottom right corner of the time tab. The number of windows should be as in the example.

Selected windows

• Selected windows should appear as green rectangles on the signal viewer. Here, the windows are synchronous on the three components as we required a common windowing.

Processing parameters

Processing tab in H/V Rotate Toolbox

• Click on the Processing tab, and make sure that parameters are as in the example window.

Output parameters

Output tab in toolbox

• Make sure you are in the Output tab, and that parameters are as in the example window.

• As mentioned before, it is impossible to save the curves in ASCII format.

Data processing

• Click on Start button at the bottom of the toolbox, whatever tab is displayed.

No selected windows pop-up window

• In case no window selection has been performed, a pup-up window appears.

Simply click on the Yes button and processing will follow its way.

Results

Signal display

Signal displayed with colored windows used for computing spectrum rotate

• Selected windows are colored.

Spectrum Rotate Graphic

Result of the computing, displaying the H/V by frequency in funtion of the direction

• The 0° direction indicates the North direction
• The 90° direction indicates the East direction

• Below the graphic displaying the the 2D H/V, there is a palette that allows the user to change the colouring characteristics of the graph.

Changing spectrum graphics appearance

Output tab showing an example to use a make-up

• It is possible to change the appearance of the spectrum graphics at the user's will using a make-up.

Saving results

Pop-up menu to save rotate data

To save the results, it is possible to create a 3 columns file where the whole data will be saved (see file example).

Browser to save rotate data

To do so, the user has to make a "right click" inside the rotate graphic to save and select "Export values". A browser will open to choose a destination folder and file name.

Pop-up menu to save rotate graphics in individual graphic

There are two solutions to save the results graphically. The first one allows saving each individual graph in independant files and the second allows saving all the graphics onto the graphic window in a single file.

• Saving the graphs in individual files
  • The spectrum graphics may be saved in various image formats.
  • Right click in the left hand margin of the spectrum graphic.
  • In the pop-up menu, choose Export image. Then choose a destination.
  • Saving individual file does not allow to save the palette in the saved graphic.

Pop-up menu to save rotate graphics in a global graphic file

• Saving all the graphs in a single file
  • Select Export image in the File sub-menu.
    

    Directory were to save the graphics
  • Choose a destination folder, image format, and file name.

Pop-up menu to save the rotate graphics in page format

• Another possibility is to save the graphic in a page format, compatible with Figue. In this case,
  • Select Save as... in the File sub-menu. A pop-up menu appears.
    

    Directory were to save the graphics
  • Choose a destination folder, image format, and file name.