Resonance proximity
Committed structural frequencies reviewed against the site's f₀ — the soil-structure resonance screening earthquake engineers actually perform.
f₁ vs f₀ ⋅ one view
HVSR — Seismic site characterization
Read the structure.
Read the ground it stands on.
Modal Master ships a complete horizontal-to-vertical spectral ratio workflow inside the OMA platform: SESAME reliability and clarity criteria evaluated item by item, directional H/V, f₀ stability analysis, and native strong-motion formats — structure and site, in one instrument.
0CRITERIA
SESAME reliability + clarity checks, itemized pass/fail.
f₀STABILITY
Fundamental frequency tracked across windows and azimuths.
H/VDIRECTIONAL
Azimuthal H/V for directional site response.
.V2+ SMC · SAF
Strong-motion formats ingested natively.
The incumbents grew out of mechanical vibration labs. Earthquake engineering asks a question they never built for: what does the site do to the structure? None of the major integrated OMA suites ships HVSR. Modal Master has it in the box.
— Why site characterization lives inside an OMA platform
01 — SESAME, itemized
Nine criteria. Each one shown.
Nine criteria. Each one shown.
Pass and fail.
The SESAME Guidelines (2004) define when an H/V curve is reliable and when its peak is clear. Modal Master evaluates every criterion on every curve and prints the measured value beside the threshold — not a single traffic light, but the full checklist a reviewer expects.
- The peak frequency exceeds ten cycles per window:
f₀ > 10 / Lw— enough of the wavefield in every window to trust the estimate. - A significant cycle count across the whole record:
nc(f₀) > 200— the peak is built from statistics, not from a lucky segment. - Bounded amplitude scatter near the peak:
σA(f) < 2over 0.5 f₀–2 f₀ (relaxed to< 3for f₀ below 0.5 Hz).
- A trough below the peak: some
f⁻in [f₀/4, f₀] with amplitude underA₀/2. - A trough above the peak: some
f⁺in [f₀, 4 f₀] with amplitude underA₀/2. - The peak actually stands out:
A₀ > 2. - The peak stays put under its own uncertainty band:
fpeak[A(f) ± σA(f)] = f₀ ± 5%. - Frequency scatter within the SESAME bound:
σf < ε(f₀), with the threshold taken from the guideline's frequency class. - Amplitude scatter within the SESAME bound:
σA(f₀) < θ(f₀), likewise class-dependent.
Criteria as defined in the SESAME European research project guidelines for H/V spectral ratio (2004). Modal Master reports each criterion individually with its measured value; the verdict is auditable, never a black box.
02 — Beyond the single curve
A peak is a claim.
A peak is a claim.
Stability is the proof.
DIRECTIONAL H/V
Site response has a compass bearing.
Sedimentary basins, ridges, and buried topography make site amplification directional. Modal Master computes H/V across azimuths, so a peak that only exists in one direction is seen for what it is — and genuine directional resonance is documented instead of averaged into blur.
- AzimuthalH/V evaluated across rotation angles, not just the geometric mean.
- AnisotropyDirectional peaks flagged and visualized for the report.
f₀ STABILITY
The fundamental frequency, over time.
A defensible f₀ must hold across the recording, not just in the average. The stability analysis tracks the peak across time windows, exposing drift, transient contamination, and the windows that disagree — so the reported site frequency is the one the whole record supports.
- WindowedPer-window peak tracking across the full record.
- ScatterDispersion shown against the SESAME bounds, not hidden behind a mean.
03 — The data you actually have
Strong-motion records,
Strong-motion records,
ingested natively.
Site work runs on the formats seismic networks produce. Modal Master reads them directly — no conversion scripts, no metadata loss on the way in.
.V2 / .V2CProcessed strong-motion records, read as delivered by the network.
.SMCStrong-motion CD format, ingested with its station metadata.
SAFSimple ASCII Format — import and export, for interchange with the ambient-vibration ecosystem.
AmbientThe same session handles TDMS, CSV/TXT, and XLSX ambient data — site and structure side by side.
04 — One instrument
Structure and site,
Structure and site,
on the same desk.
The question that decides retrofit budgets is a comparison: where the structure's committed frequencies sit relative to the site's fundamental frequency. When the OMA result and the H/V result live in one platform, that comparison is a workflow — not a data-wrangling project between two tools.
Site studies at scale
SESAME-graded H/V curves with itemized verdicts, ready for microzonation and site-classification deliverables.
SESAME ⋅ itemizedHistoric structures
Ambient identification plus site characterization in a single visit — the low-impact survey heritage work demands.
structure + site ⋅ one visitPrivate demonstration
Bring a site record.
Leave with a verdict.
Watch an H/V curve go from raw record to itemized SESAME verdict — every criterion, every measured value, every threshold — alongside the modal survey of the structure itself.
Enterprise evaluations · Technical dossiers under NDA · Volume licensing