What is Resistivity Surveying?

Introduction to Resistivity Surveying

Resistivity surveying is a crucial geophysical exploration technique widely used in geological surveys, mineral resource exploration, environmental monitoring, and engineering inspections. This article provides a comprehensive and in-depth reference for professionals and researchers in related fields by detailing the definition, principles, methods, advantages and disadvantages, application differences, and case studies of resistivity surveying.

Definition and Principles of Resistivity Surveying

Resistivity surveying is a method that infers the geological structure underground by measuring the variation of resistivity of rocks or soils with depth. Resistivity is an electrical property of matter that reflects the degree to which matter impedes current flow. Different types of rocks and soils have different resistivity characteristics, providing the basis for the application of resistivity surveying.

High-Density Resistivity Method

The high-density resistivity method is an advanced resistivity surveying technique that quickly acquires high-resolution underground resistivity distribution information by arranging a large number of electrodes along a survey line and using automated equipment for data collection. It is suitable for complex geological conditions and large-area exploration work due to its fast measurement speed, high data accuracy, and ability to perform two-dimensional and three-dimensional imaging.

DC Resistivity Sounding

DC resistivity sounding is one of the traditional resistivity surveying methods. It calculates resistivity by injecting direct current into the ground and measuring the potential difference. It is simple in equipment, easy to operate, and low in cost, but it is relatively lacking in data acquisition speed and resolution compared to the high-density resistivity method.

2D and 3D Electrical Resistivity Imaging Methods

Two-dimensional and three-dimensional electrical resistivity imaging methods are important directions in the development of resistivity surveying technology. Two-dimensional imaging methods acquire lateral resistivity distribution information of underground geological bodies by arranging electrodes along a survey line, while three-dimensional imaging methods reflect the three-dimensional structure of underground geological bodies more comprehensively by arranging electrodes in multiple directions. These methods have wide applications in urban geological surveys, karst detection, and groundwater pollution monitoring.

Electrical Resistivity Tomography (ERT)

ERT is an inversion technique based on resistivity sounding data. It constructs two-dimensional or three-dimensional models of underground resistivity distribution and intuitively displays the underground geological structure. ERT has significant application value in mineral resource exploration, environmental monitoring, and engineering inspection.

Induced Polarization (IP)

IP is an extended technique of resistivity surveying. It provides more geological information by measuring the polarization effect of rocks under the action of current. IP has unique advantages in mineral exploration and groundwater pollution monitoring.

Comparison and Advantages/Disadvantages of Various Methods

Different types of resistivity surveying methods differ in measurement principles, equipment requirements, data processing methods, and application ranges. The high-density resistivity method is fast in measurement, high in data accuracy, and capable of two-dimensional and three-dimensional imaging, but it is costly in equipment; DC resistivity sounding is simple in equipment, easy to operate, and low in cost, but relatively lacking in data acquisition speed and resolution; two-dimensional and three-dimensional electrical resistivity imaging methods provide more comprehensive underground geological information, but the data processing and inversion process is complex; ERT and IP have unique advantages in specific fields but require high data quality and inversion algorithms.

Application Differences and Case Studies

Resistivity surveying plays an important role in different application scenarios. In urban geological surveys, the high-density resistivity method and two-dimensional electrical resistivity imaging methods can quickly acquire underground geological structure information, providing a basis for urban planning and engineering construction; in karst detection, three-dimensional electrical resistivity imaging methods and ERT can effectively identify karst caves and underground passages, ensuring the safety of engineering construction; in groundwater pollution monitoring, IP and ERT can monitor the pollution range and migration path of groundwater, providing technical support for environmental protection.

Forward and Inversion Comparison of Data

The forward and inversion of resistivity sounding data are important links in data processing and interpretation. The forward process calculates resistivity data based on a known geological model to verify the rationality of the model and the feasibility of the method; the inversion process constructs a model of underground resistivity distribution based on actual measurement data to reveal the underground geological structure. The forward and inversion processes verify and complement each other, jointly providing a scientific basis for the application of resistivity surveying.

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