WinSism refraction seismic

of W_GeoSoft Geo2X SA

How to use the software ?

Compatibiliy

• Window 7,8 (PDF display problem)

• Window Xp (no known problem)

• Windows 95, 98 (no known problem)

• Windows 2000 & NT (Occasional compatibility problems)

• Windows Me (Few feedback…)

Few abbreviations to know

• TT= travel time

• FBP= First break point

• IT=Intercept times

• BR=Bedrock

• GRM= Generalized Reciprocal Method

• SU=Seismic Unix

First you must convert your field data to SU format

Click here

Then select your file format

To convert SEG2 to SU, just select all records of a spread

Select your records

Convert to Su format

All shots data of one spread will be recorded into one large SU file !!!, Shot order must be the same as field recording order, shot 1 = first offset, shot 2=end shot 1

First break picking is the next stepPrecise picking is fundamental!

Use the scroll bar to select record

Select the SU file

Pick the FBP(First break points)

You can enlarge trace size, clip amplitudes and more… With the mouse reduce time display

How tu use automatic picking

First, click on the smallest break time with the right button

The move the scroll to adjust all FBP automatically

If necessary adjust parameters

Picking can be corrected later

Travel time structure•To give valuable informations a seismic refraction spread MUST have at least 2 offsets, 2 end shots one center shot (see REDPATH booklet) !

•You can have up to 48 shots and 96 receivers per shot

•Distance ZERO is END SHOT 1

•Offset 1 will have a negative distance

•All receiver distances are measured from END SHOT 1

Now, we can build the travel time (1)

You must enter few data

•File name

•Geophone spacing and number

•Shot spacing and number

Build the travel time (2)

Double click on the top first cell of shot 1 and the select the corresponding FBP file.Repeat for all shotsTime delay can be added to all times

FBP files can be renamed when used or reversed

Build the travel time (3)

Repeat for all shot and correct if necessary shot location and elevation

Click on SAVE and DISPLAY

Build the travel time (4)

Display and control the travel time

Zoom is possible

Travel time correction 1

Select and display the SU file

Click on the FPB to correctTravel time is updated automatically

If necessary adjust display parameters

Travel time correction 2

Correct the value on the grid then click on SAVE and DISPLAY button

You can move any FBP time, double click on a point, keep pressed and release the mouse at the new correct location. To delete a point, double click on it and release without moving.

Travel time correction 3

Bed rock velocity determination

To know the BR velocity use the true velocity between the two offset shots

If you have not a straight line, you can have more than one BR velocity

If you know the number of layers save the BR velocity

Travel time movingYou can move the offset shot down to the End shot

You can determine:1. Which part of

the End shot belongs to bedrock

2. The intercept time for the end shot (Save it)

Bedrock arrivals

First and second layer arrivals

Velocity determination (1): Linear regression

Select a shot first and last geophone

Compute using linear regression and save the velocity for the correct layer number

Velocity determination (2)

You can draw a line with the mouse (Down, move Up), velocity is computed and can be saved (Menu PROCESSINGVELOCITY DETERMINATION)

Depth computation Intercept Time method

When all layer velocities and IT have been determined, you can compute the layer thicknesses and BR depthSelect shotComputeSave if not automatic

Coloured profile display (1)

Select the PROFILE PARAMETER tabAnd enter your choices Profile elevation and thicknessDraw shot or/and geophones

Click here to prepare the profile

Coloured profile display (2)

This graph can be saved as WMF, JPG file or copy into the clipboard and PASTE into any program (WORD, PAINT, CORELDRAW)Click on right button to launch graph editor

ABC method (1)

Move down the offset travel time to fit as well as possible on the end shots

ABC method (2)

Move the total time line down to the end of shots

You can now compute time from surface to bedrock below all geophones

Delay times give a good idea of bedrock geometry, like furrows

ABC method (3)

If you already compute depth below shots, you can know the bedrock depth below all receivers

ABC method (4)

You can also display a ABC coloured profile

GRM method (1)

This method is not suitable if you have less than 24 geophones

First have a look on the velocity fonction curve to select the receiver spacing

See the PALMER thesis PDF file in the W_GeoSoft CD-ROM for all theory

GRM method (2)

Then the Time depth curve is drawn

GRM method (3)

Last step, depth computation below all geophones and save the values in the GRM grid file

GRM method (4)

Using the GRM file, you can draw a coloured profile of GRM depth computation

Quick interpretation

You can have easily a first idea of depth with the QUICK INTERPRETATION module. The

Just select the shot number, the number of layer and move the layer limit

You can save depth and velocities in the WinSism WS4 file

WinSism menu

Display a TT Read a WinSism file Save a WinSism file Convert field records

FB picking Redisplay TT File info Correct a TT Build TT

Quick interpretation Trace moving Velocity linear regression Velocity point to point Velocity line True velocity

Thickness computation Printing Display profile ABC method GRM Method Zoom

Help Ruler EXIT

Most of the operations can be launched using pictograms or shortcuts