Quickstart — your first calculation in 5 minutes

In 5 minutes you see RSL III working on a sample stratigraphic column.

1. Open the app

Go to nx.geostru.ai/rsl/.

2. Load a sample

Top toolbar → Samples → pick a ready-made case (e.g. "Saturated sand on bedrock — Central Italy M=6.0").

The sample populates:

• Stratigraphy: 4-6 layers with realistic Vs, γ, G/Gmax and ξ curves
• Input accelerogram: real seismic record (e.g. from ITACA)
• Reference bedrock (Vs > 800 m/s) as the base of the column

3. Run the calculation

Press Run calculation at the top. RSL III:

1. Discretises the column into sub-layers (step chosen automatically from Vs and f_max)
2. Initialises G = G_max and ξ = ξ_min for each layer
3. Computes the transfer function from bedrock to surface (reflection/transmission coefficients method, frequency domain)
4. Estimates γ_max for each layer; updates G and ξ by reading the degradation curves
5. Iterates until γ_eff changes by less than the tolerance (~0.5%) — typically 4-8 iterations

Time: 1-3 seconds for a 20-50 m column.

4. Inspect the results

The main outputs you see:

Surface response spectrum

The PSA (Pseudo Spectral Acceleration) compared with the reference NTC spectrum for the site. Where the RSL PSA exceeds the NTC one are zones of local amplification that the site imposes on the structure.

γ_max, a_max, σ_max profiles

For each depth along the column, shows:

• γ_max (maximum shear strain, in %) — layers with γ > 0.1% are in a significantly non-linear regime
• a_max (peak acceleration) — amplification from bedrock to surface
• σ_max (maximum shear) — useful for liquefaction and stability checks

ICMS amplification factors

FA (amplification factor, short periods 0.1-0.5 s), FH (long periods 0.4-0.8 s) and FT (all periods) — the three indicators required by Italian Level 3 seismic microzonation (ICMS 2008/2018).

More on ICMS factors →

5. Export the Word report

Toolbar → Report. Download the .docx with:

• Cover page + input data
• Tabulated stratigraphy + degradation curves
• Input accelerogram + Fourier
• Surface response spectrum + NTC comparison
• γ_max, a_max, σ_max profiles
• ICMS amplification factors
• Conclusions

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Next steps

• Complete workflow — a real project from start to finish
• Equivalent-linear method — how the calculation works
• ICMS — amplification factors for microzonation
• Input data — complete description of every field

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