1. Importing Input Data
Seismic Data with Source/Receiver (SR) Setup [*(SR).dat]
In the main menu, go to "Process" → "Common-Offset (CO) Section" and then select the sample data in "...\Sample Data\VOID\VOID(SR).DAT."
2. Generating Common-Offset (CO) Sections
The following dialog will show up that has options for output trace arrangement. Click the indicated button to specify the output file name. Then, the generation will be automatically executed and the output will be displayed.
To zoom in the top 1-sec portion of the output, select the "View" tab, press the "zoom-in" button once and then drag mouse to encompass the portion of display as illustrated below.
The record number displayed on top indicates the corresponding common offset multiplied by 100; for example, "600" for 6-m common offset as illustrated below. Different common-offset sections can be viewed by pressing one of the four record-scan buttons, one of which is indicated below, in the "Data" tab. One side of the symmetric scattering feature on a common-offset section, which appears similar to the hyperbolic arrival pattern of body-wave diffraction, can be identified as slant (sloping down from right to left) patterns originating from the corresponding surface location (44-m).
Another common-offset (17-m ) section is displayed below that shows the similar feature from the void location.
This shows the longest common-offset (29-m) section.
3. Horizontal Event (HE) Filtering
Usually, the scattering feature can be enhanced by filtering out the horizontal arrivals by using the "Horizontal Event (HE)" filtering. For that, select "Process" tab in the BSA display window. Then, right-click the "Filter" button to display the dialog shown below. Check "Save output" and enter "VOID(SR)(CO)(HE=5)" for output file name when prompted as illustrated in the "Save As" dialog.
Then, (normal) click the "Filter" button and double click any place in the display as illustrated below.
Choose "Horizontal Events", specify a value (e.g., "5") in the "Horizontal Window (%)", and then click OK button to execute the filtering for all records. A value less than or equal to 5 (%) is usually optimal. A smaller number would be necessary if the horizontal event has the higher dominant frequency, and vice versa. Click "Yes" to display output.
Display normalization option can be changed by using the button (1) in the "View" tab. Surface coordinates of the display can also be chosen for trace number (2), station number (3), and the survey-line distance (3) buttons, last two of which (3 & 4) represent the source-receiver center coordinates.
Double click any place in the display to show the following control dialog in which all the display characteristics can be modified. For example, labeling characteristics on the horizontal (surface) and vertical (time) axes can be changed in the "Labeling" tab as shown below.
The following section shows the horizontal coordinate of the center station number between source and receiver for the shortest common-offset (6-m) section.
The following section shows the horizontal coordinate of the center station number between source and receiver for the intermediate common-offset (17-m) section.
The following section shows the horizontal coordinate of the center station number between source and receiver for the longest common-offset (29-m) section.
