PolarStiff: Anisotropic G0 Profiler for Seismic Site Response
Software that turns routine clay site-investigation data (void ratio, stress history, geologic age) into direction-dependent small-strain stiffness profiles for earthquake site response, correcting the common assumption that clay stiffness is identical in every direction of wave polarization.
Concept
PolarStiff is a tool for seismic site response engineers. The user enters what routine site investigations in clay already produce: layer stratigraphy, void ratio (or index properties), effective stresses, overconsolidation ratio, and the unloading/aging history of each clay layer. The tool returns a depth profile of the small-strain shear modulus G0 for each plane of polarization relative to the in-situ principal stress directions — separate stiffness values for differently polarized shear waves — with uncertainty bands, and exports them in the input formats of standard 1D/2D site response codes (e.g., DEEPSOIL, STRATA). The single wedge: replace the customary single isotropic G0 per layer with polarization-dependent values, so amplification analyses in clay basins stop carrying a documented, correctable bias. Calibration rests on the six-Italian-clay dataset of paired in-situ and laboratory measurements.
Why now
Paper [0] reports a combined in-situ and laboratory campaign on six different Italian natural clays, with laboratory G0 measured on high-quality undisturbed specimens reconsolidated to the best estimate of the in-situ geostatic effective stresses. It demonstrates that G0 is governed by (i) soil state — the combination of current void ratio and acting effective stress, (ii) overconsolidation arising from both unloading and aging, and (iii) the plane of polarization with respect to the principal stress directions for seismic body waves. Factor (iii) is the commercially decisive one: it shows that today's isotropic-G0 site response practice in clays is measurably incomplete in a specific, correctable way, and the paper supplies the parameter dependencies needed to build that correction into a profiler. Paper [1] supplies the underlying soil-state/stiffness framework the tool's correlations rest on.
Written by GLM · 10 Oct 2026
AI assessment
A highly focused, scientifically grounded tool that solves a specific technical bias in seismic engineering using a clear data-driven wedge.
- Evidence strength 5/5
- The idea directly implements the findings of Paper [2], which provides the specific experimental data on six Italian clays to quantify the effect of polarization on G0.
- Market pull 4/5
- The target users (seismic engineers and agencies like INGV) have a high urgency for accuracy in microzonation, and the tool integrates into existing workflows (DEEPSOIL/STRATA).
- Novelty & moat 5/5
- Unlike the general-purpose SoilTwin, this focuses on a specific, overlooked physical phenomenon (anisotropy of G0) and provides a direct correction for a known industry bias.
- Feasibility 5/5
- The MVP is essentially a software implementation of the correlations and datasets provided in the cited research, requiring no new lab discovery.
- Wedge clarity 5/5
- The wedge is extremely sharp: replacing a single isotropic G0 value with polarization-dependent values in standard site-response inputs.
- Simplicity / focus 5/5
- The product is a single-purpose profiler with a clear input-output loop, avoiding the 'platform' trap.
Scored by Gemma 4 · 10 Oct 2026. Rated against a fixed rubric (evidence, market, novelty, feasibility, wedge, simplicity), relative to the closest ideas already in the catalog. A prior estimate to compare ideas before real-world signal arrives.
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Who benefits
INGV supports Italy's municipal seismic microzonation studies; polarization-dependent G0 profiles directly improve the site-response layer of those studies in Italian clay deposits.
- Dipartimento della Protezione Civileorganization
Italy's Civil Protection Department coordinates seismic microzonation programs for municipalities; a calibrated, clay-specific anisotropic G0 profiler standardizes stiffness inputs across Level 2/3 microzonation deliverables.
- GeoStru Softwarecompany
This Italian geotechnical software vendor could integrate the profiler as a differentiated, Italy-calibrated stiffness module inside its seismic and geotechnical product line.
The Italian geotechnical consultancy routinely runs site response studies on Italian clays; the tool converts its standard lab data into defensible anisotropic G0 profiles without new testing campaigns.
- Arupcompany
Arup's seismic design practice would use polarization-dependent G0 to reduce systematic bias in clay-basin ground-motion amplification analyses for buildings and infrastructure.
Research it builds on
- Fundamentals of Soil BehaviorJames K. Mitchell, Kenichi Soga, Catherine O’Sullivan · 2025 · 3023 citationsAll ideas from this paper →
- Remarks on the stiffness at small strains of six Italian claysMichele Jamiolkowski, Renato Lancellotta, Diego Carlo Lo Presti · 2026 · 148 citationsAll ideas from this paper →