How To...

1) Setting vertical and horizontal scales on 2D profiles Does SurfSeis 3 have the ability for the user to set the vertical and horizontal scales on 2D profiles?

2) Changing assigned mode numbers In selecting higher modes, is it possible to pick dispersion curves and to change the number of the mode that has been assigned, in order to do tests with different mode numbers for a given dispersion curve?

3) Emulate roll-along with a fixed spread How to use a fixed spread with SurfSeis software to emulate a roll-along data acquisition pattern (and avoid the "No variation along x-axis" error message).

4) How can I create a .grd file from a three-column text (.txt) file in SurfSeis?

5) How do I use my own density, velocity, and/or Poisson's ratio values with SurfSeis 3?

6) Can data be presented in 3D using SurfSeis?

7) How do we deal with velocity increasing with frequency dispersion curves (a.k.a., Lamb wave patterns)?

8) How can I reproduce the default interpolation which is used in SurfSeis to generate a 2D Vs map in Surfer?

9) How to Make 2-D Images Show Distance (m or ft).


1) Does SurfSeis 3 have the ability for the user to set the vertical and horizontal scales on 2D profiles?

[SurfSeis3] Yes, the outputs are text files that can be easily modified as needed (with Excel, for example).

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2) In selecting higher modes, is it possible to pick dispersion curves and to change the number of the mode that has been assigned, in order to do tests with different mode numbers for a given dispersion curve?

[SurfSeis3] Yes, you can edit the .DC file by clicking View, (Edit) Dispersion Curves on the menu, and delete/add points for every mode. You can also edit the .DC file as a text file and change the mode number digit (the last digit in each row).

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3) How to use a fixed spread with SurfSeis software to emulate a roll-along data acquisition pattern (and avoid the "No variation along x-axis" error message).

If you have estimated the necessary number of seismic spread channels (say, 24) and you have the ability to acquire data using a larger number of channels (say, 48), then you may find it more labor efficient to acquire MASW data using a fixed spread. Seismic records can be obtained by shooting from off one end of the spread (first shot outside the spread) and then continuing shooting into the spread (moving the source toward the middle of the spread). Then, from the data acquired in such a manner data, record traces can then be extracted (cut) to emulate a roll-along data acquisition pattern with a smaller spread (e.g., having 24 channels).

Example:
Assume the 48 geophones are located on stations 1001-1048 and a total of 13 seismic records were shot (acquired) with the source located at stations 999, 1001, … through 1023 for the records numbered from 101 to 113. SurfSeis can help you pull out (extract, cut) thirteen 24-channel records using the following steps.

  1. Convert data from SEG2 to KGS format (say, line1.dat).
  2. Apply geometry information (Field Setup) into the trace headers.
  3. Click 'Display,' then 'Seismic' buttons, and open the converted kgs data file (say, line1.dat).
  4. Find the "scissors" button located at the top right corner of the window displaying seismic data. (The "scissors" button is located on the row containing the pointing-hand buttons. If you do not see these buttons, click the 'Record…' label to activate/deactivate that row of buttons). Click the "scissors" button to display a 'Cut Records' window containing three tabs ('Record,' 'Trace,' and 'Time').
  5. At the 'Record' tab select the end record at the 'End' drop box, or check the 'All Records' checkbox.
  6. Click 'Save Output As' button to specify the output file name (the default in this example would be line1(CUT).dat.)
  7. At the 'Trace' tab select the 'Begin' and 'End' trace numbers (e.g., 1 and 24). At both Increment boxes select 2 (this is because your source moved with 2 geophone intervals, i.e., 999, 1001, etc.)
  8. Click the 'OK' button to extract (cut) the new set of records each containing now only 24 traces.
  9. Open the new file (e.g., line1(CUT).dat) and go through the records using the pointing-hand buttons to make sure you have extracted the intended range of traces from each record.

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4) How can I create a .grd file from a three-column text (.txt) file in SurfSeis?

You can always make a .grd file from a .txt file by choosing from the menu "View," "2-D Vs Image," click the "Open" button, and from the "Files of type" select *.txt files to display. Chose a .txt file and the software will make a grid for you. You can change the interpolation algorithm by right-mouse-button clicking on the image, choosing "Options" and under the "Settings" tab there is an "Interpolation Algorithm" radio button. After making a new choice, click the "Update Image" button to make the new grid.

The Kriging algorithm can be data demanding and in some cases may not work. If this is the case, then you can switch to Bilinear. In addition to the menu approach you can change it through the corresponding .INI file. SurfSeis remembers the used algorithm in the text file "INTPScheme.INI," which resides in the \INI subfolder of your SurfSeis install folder. There you can change "Kriging" to "Bilinear," if needed, and then start the program, which will use the specified algorithm.

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5) How do I use my own density, velocity, and/or Poisson's ratio values with SurfSeis 3?

To use your own model, including different density, Vp, and/or PR ratios you need to select the "Fixed Vs model" radio button, which is located under the "Initial Vs Layer" tab of the "Inversion Controls" window (that is activated by clicking the "Controls" button"). SurfSeis 4 provides flexible options for using initial models (see SurfSeis 4 manual).

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6) Can data be presented in 3D using SurfSeis?

The MASW method estimates a 1-D vertical Vs profile from a seismic record. When multiple records are acquired moving their position along a line, the resulting 1-D Vs profiles can be assembled into a 2-D vertical cross section (a.k.a, in a x-z plane). Similarly, when seismic data is acquired across a broad surface area (e.g., along several parallel lines) the 1-D Vs profiles can be assembled into a 3-D Vs volume image.

SurfSeis provides the tools for 2-D imaging for user convenience and provides results in a 3-column text format, such that they can be used by third-party software specialized in gridding (e.g., for irregularly spaced data) and imaging such data in 2-D and 3-D (e.g., Arc GIS, QuickSurf, Surfer, Voxler, etc.).

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7) How do we deal with velocity increasing with frequency dispersion curves (a.k.a., Lamb wave patterns)?

Please see this Acrobat PDF on "Lamb Wave Patterns."

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8) How can I reproduce the default interpolation which is used in SurfSeis to generate a 2D Vs map in Surfer?

Very often Kriging with anisotropy ratio 2/1 to 4/1 can produce similar results.

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9) How to Make 2-D Images Show Distance (m or ft).

Please see this Acrobat PDF.