Welcome to the ABEM Vs30 Guidance Tool
This step-by-step guide will take you through the process of collecting quality seismic data to undertake Vs30 analysis. This guide is optimized for mobile devices.
NOTE: Vs30 surveys require 4.5Hz vertical geophones
With the set-up wizard on the screen of the instrument, click start, below.
>> START <<
Settings and field procedures are based on recommendations published by Park et al.
Click for more information
Step 1a: Instrument Settings
Select 24 channels in the Terraloc Set-up Wizard
(use single cable option for 48 channel instruments)
Select Vs30 from the drop-down menu
Select the green “NEXT” button
Step 1b: Instrument Settings
On the second page of the Terraloc Set-up Wizard, select 2m geophone spacing and hammer source.
Press “OK”
Step 2: Cable / Geophone Layout
This is a generic layout for a Vs30 measurement with 24 geophones.
If you have a 48 channel instrument, use only the first cable to provide 24 channels.
Geophone spacing should be 2 metres
Step 3a: First Shot Position / Trigger Connection
Place shot plate 48m from Geophone 1
Trigger connection via trigger wire
Place a spare geophone next to the shot plate and connect to the trigger reel.
The far-end of the trigger reel should be plugged into the “Analog. Trig In” trigger connection on the instrument end-panel.
It is possible to use a wireless trigger connection, see here for more information.
Step 3b: Set-up Layout Geometry
Open the Layout Geometry window by pressing 6 on the front panel of the instrument
Enter shot position x: -48m
Step 4: 1st Shot
Example shot record from a -48m off-end shot:
Data look different? Try our Troubleshooting Guide
Optional Step 4a: Dispersion Analysis
If you want to check that the shot will produce a good dispersion curve (the basis for Vs30 processing) press CTRL + ALT + ENT to open the Dispersion Analysis Tool.
Once open, navigate using the arrow keys, backspace and enter to open the most recent shot record.
Optional Step 4b: Dispersion Analysis
Accept default parameters on first run, by pressing ENT, and wait for results to appear.
This process can be followed for each shot, just press ESC to return to the main instrument software.
Data look different? Try our Dispersion Curve Guide
Step 5: 2nd Shot
Update shot position to -24m in Layout Geometry
(press 6 on the front panel)
Example shot record from a -24m off-end shot:
Data look different? Try our Troubleshooting Guide
Step 6: 3rd Shot
Update shot position to -12m in Layout Geometry
(press 6 on the front panel)
Example shot record from a -12m off-end shot:
Data look different? Try our Troubleshooting Guide
Step 7: 4th Shot
Update shot position to -2m in Layout Geometry
(press 6 on the front panel)
Example shot record from a -2m off-end shot
Data look different? Try our Troubleshooting Guide
Step 8a: 5th Shot
Place shot plate 2m from the last geophone
Enter shot position as 48m in Layout Geometry
(press 6 on the front panel)
Remember: the distance entered is from the first geophone (0m in the spread)
Data look different? Try our Troubleshooting Guide
Step 8b: 5th Shot
Example shot record from a 2m off-end (48m) shot:
Data look different? Try our Troubleshooting Guide
Step 9: 6th Shot
Update shot position to 58m in Layout Geometry
(press 6 on the front panel)
Example shot record from a 12m off-end shot:
Data look different? Try our Troubleshooting Guide
Step 10: 7th Shot
Update shot position to 70m in Layout Geometry (press 6 on the front panel)
Example shot record from a 24m off-end shot:
Data look different? Try our Troubleshooting Guide
Step 11: 8th Shot
Update shot position to 94m in Layout Geometry (press 6 on the front panel)
Example shot record from a 48m off-end shot:
Data look different? Try our Troubleshooting Guide
Step 12: Transfer Data
Using Android device?
Connect your phone via USB to the Terraloc Pro 2 and allow access on your device.
The Terraloc will see your device as an external storage location, use the CTRL + SHIFT + LEFT ARROW shortcut to access the file explorer and move files across.
Using ALT + TAB will take you back to the Terraloc Pro 2 software.
Using USB drive and PC
Connect your USB drive to the Terraloc Pro 2 and this will be used as the destination for the Quick Backup function on the instrument.
Step 13: Process / Analyze Data
Processing requires 3rd party inversion software such as Geogiga
Step 14: Generic Processing Workflow
The 8 shots are processed individually, each creating a velocity model, these results are correlated to generate a combined velocity model, summarised by the Vs30 value.
IMPORT DATA
& QUALITY CHECK
|
GENERATE
DISPERSION CURVES
|
PICK THE LINE
OF THE CURVE
|
RUN INVERSION ON
THE PICKED CURVE
|
COMBINE RESULTS TO GENERATE
AVERAGE VELOCITY MODEL
|
COMPARE Vs30 VALUE
AGAINST AGREED STANDARD
(after BSSC, 1997*)
*Building Seismic Safety Council (BSSC), 1997, NEHRP, recommended provisions for seismic regulations for new buildings, Part 1-Provisions (FEMA Federal emergency Management Agency 302), 290 p.