Ground engineering · Earthquake geotechnics
Site period & Vs30 from layers calculator
Time-averaged shear-wave velocity over 30 m, average Vs of the soil column and fundamental site period.
Standard: Vs30 = 30/Σ(hi/Vsi) · T = 4H/Vs
Open the live calculator → All ground engineering calculators
Inputs in the worked example
The live calculator starts with these values; change any of them and every result, check and diagram updates instantly.
| Input | Value | Unit |
|---|---|---|
| Layers: thickness (m), Vs (m/s) | 4, 160 6, 220 10, 350 15, 600 |
Worked example — results
| Result | Value | Unit |
|---|---|---|
| Vs30 = 30/Σ(h/Vs) | 307.7 | m/s |
| Total thickness | 35.00 | m |
| Average Vs of column | 330.7 | m/s |
| Site period 4H/Vs | 0.423 | s |
- ✓ Profile reaches 30 m
Method, formulas and assumptions
- Vs30 = 30/Σ(h/Vs) = 30/SUM([t.tt]) = 307.66 m/s
- Total thickness = SUM([t.h]) = 35 m
- Average Vs of column = 35/SUM([t.tt2]) = 330.67 m/s
- Site period 4H/Vs = 4*35/330.67 = 0.42338 s
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For preliminary design and education. Check every result against the current standard and your own engineering judgement before use.