Target-Driven Integrated Near-Surface Geophysics: A Framework for Method Selection and Multi-Method Interpretation

Abstract Near-surface geophysics provides non-invasive tools for characterising the shallow subsurface across geotechnical, environmental, infrastructure, archaeological, and security-related applications. Yet the shallow subsurface is highly heterogeneous, and no individual method is universally capable of resolving all relevant targets, depths, and physical properties under all site conditions. This narrative review compares three major methodological families used in shallow subsurface investigations: seismic methods, ground-penetrating radar (GPR), and electromagnetic (EM) methods including transient electromagnetics (TEM) and electrical resistivity tomography (ERT). Their physical sensitivities, acquisition characteristics, processing and inversion approaches, resolution scales, and site-specific failure modes are examined with emphasis on the complementary information provided by elastic, dielectric, and electrical-property contrasts. Building on this comparison, a seven-step target-driven framework is proposed for method selection, integrated survey design, co-registration, joint interpretation, validation, and uncertainty reporting. The framework is operationalised through a decision matrix that maps target type, physical contrast, site conditions, and investigation depth to recommended method combinations, integration levels, and known failure modes. Five levels of integration rigour are distinguished, from side-by-side display to full probabilistic joint inversion, enabling practitioners to select the approach appropriate to the available data quality, computational resources, and decision context. The paper also discusses the limitations of multi-method integration, including scale mismatch, co-registration errors, structural coupling assumptions, petrophysical model uncertainty, and the risk of artificial agreement in joint inversion results. Representative application domains — cavity detection, archaeological prospection, seawater intrusion, geotechnical site investigation, and infrastructure assessment — are discussed with explicit reference to the framework. Recent advances in full-waveform inversion, joint petrophysical inversion, passive seismic methods, multi-channel GPR, and machine learning are reviewed. The central conclusion is that integrated near-surface geophysics is most effective when method combinations are selected from the expected target physics and site constraints, interpreted within a common spatial and uncertainty framework, and validated against independent ground truth rather than simply compared post hoc.