What Are Geophysical Methods? The Ultimate Technology Handbook

1. Core Concepts & Method Classifications

1.1 Definitions & Scientific Basis

Geophysical Methods are non-destructive techniques that infer subsurface structures by measuring geophysical fields (electromagnetic, seismic waves, etc.). They are categorized as:

• ​Passive Methods: Utilize natural fields (gravity, geomagnetism)
• ​Active Methods: Employ artificially induced fields (electrical currents, seismic waves)

Technical Essence: Inversion algorithms convert surface observations into subsurface physical property distributions, with resolution exponentially decreasing with depth1.

1.2 Mainstream Method Matrix

Method	Physical Parameter	Detection Depth	Typical Equipment
​High-Density Resistivity (HDR)	Resistivity	10-500m	Geotech GIM
​ERT	3D Resistivity	5-300m	Geotech WGMD
​GPR	Dielectric Constant	0.1-30m	Geopro T-Series
​Seismic	Wave Velocity/Impedance	50-5000m	GE-ANT-1C

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2. Technical Comparisons & Innovations

2.1 Resistivity-Based Methods

High-Density Resistivity Method

• Principle: Automated multi-electrode arrays (60-120 channels) generate 2D/3D resistivity profiles
• Advantages:
  • 5x faster data acquisition than traditional DC methods
  • Digital filtering achieves 80dB SNR in urban environments
  • Identifies karst conduits <5m diameter

ERT (Electrical Resistivity Tomography)

• Innovations:
  • ConvResNet AI inversion reduces 3D modeling from 24h to 1.8h
  • 1000V high-voltage system enables 300m penetration

2.2 Electromagnetic Wave Methods

GPR (Ground-Penetrating Radar)

• Frequency Selection:
  • 100MHz: Municipal pipeline detection (10m depth, 0.3m resolution)
  • 2.6GHz: Concrete defect inspection (0.5m depth, 2cm resolution)
• Case Study: Identified 22,370m³ karst cavities in Wuhan using multi-frequency GPR

2.3 Advanced Seismic Applications

• ​Microseismic Monitoring: ±3m positioning accuracy for CO₂ storage leakage warning
• ​Surface Wave Survey: MASW technique inverses shear wave velocity within 50m depth

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3. Industrial Applications & Cost Efficiency

3.1 Mineral Exploration

• ​Orebody Delineation:
  • 3D ERT differentiated silicified zones (ρ>2000Ω·m) in Guangdong Pb-Zn mines with <8% error
  • Reduced exploration costs by 40% through integrated surveys

3.2 Geotechnical Engineering

• ​Subway Tunnels: GPR+MSSW combination detected boulder clusters in shield tunnel zones
• ​Dam Monitoring: Time-lapse ERT tracked embankment core saturation changes with ±2% accuracy

3.3 Environmental Management

• ​Contaminant Monitoring: TEM+ERT synergy mapped VOC plumes in industrial sites
• ​Permafrost Thaw: UAV infrared + ANS interferometry warned of thaw hazards

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4. Equipment Selection & Technological Breakthroughs

Geotech Series Solution Matrix

Product Line	Key Innovations	Application Scenarios
​GIM Series	120-channel AI switching	3D metal ore modeling
​Geological Radar	Multi-frequency synchronization	Urban road collapse warning
​Seismic nodal	500-node wireless network	Site seismic risk assessment

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References

• ​GPR basic principles
• Ground-penetrating radar (GPR) methodology:https://www.sciencedirect.com/topics/earth-and-planetary-sciences/ground-penetrating-radar(Describes the principle of GPR as a high-frequency electromagnetic wave reflection method)
• ​Multi-frequency GPR applications
• Multi-frequency GPR systems in civil engineering:https://www.ndt.net/article/v11n07/loizos.pdf(Describes the relationship between 100MHz-2.6GHz frequency band selection and detection depth)
• ​ERT and GPR joint exploration
• Integrated geophysical methods (ERT+GPR):https://link.springer.com/article/10.1007/s12665-021-09775-4(Illustration of the case of resistivity tomography and radar collaborative detection of karst)
• ​Modern GPR system parameters
• Study on the effectiveness of ALS+GPR+Geoelectrics combination:https://www.researchgate.net/publication/327456723(Verification of multi-method collaboration in archaeological and geological surveys)