Inversion Frameworks

At sites with strong impedance contrasts, such as soft soil over shallow rock, Rayleigh-wave energy shifts smoothly from the fundamental to higher modes at low frequencies. This mode jump is easy to miss, and treating it as the fundamental mode overestimates deep Vs and misplaces bedrock. Predominant-mode inversion automatically uses, at each frequency, the mode with the largest vertical surface amplitude.

 ✅No mode numbering or fundamental-mode assumption needed

 ✅Works with combined active (MASW) and passive (MAM) data

 ✅Recovers velocity contrasts and bedrock depth accurately

 ✅Validated at the I-15 Downhole Array against PS logs

Ref: Bhaumik & Cox (2026), Engineering Geology 

A measured dispersion image is not a single theoretical mode: it is a superposition of modes, body waves and near-field energy, shaped by the source-receiver layout. Effective-mode inversion models this directly. The HTLM active-source wavefield is computed for the actual survey geometry, and the resulting effective dispersion curve is matched to the data with particle swarm optimization.

 ✅Accounts for near-field effects and modal superposition

 ✅Handles mode kissing, higher-mode skipping and stiff layers

 ✅Captures offset-dependent behavior of real surveys

 ✅Removes subjective mode identification

Ref: Bhaumik & Naskar (2026), Géotechnique