Journal of Geology & Geophysics
Open Access

An Overview on Geophysics of the Shallow Subsurface

Naoko Yoshida^{* *}Correspondence: Naoko Yoshida, Department of Geosystems, Graduate School of Engineering, Tokyo University, Tokyo, Japan, Email:

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Description

The shallow subsurface of the Earth, extending from the surface to a few hundred meters below, holds a treasure trove of information about our planet's history, resources, and environmental conditions. Exploration geophysics is the key to unlocking these hidden secrets. Through a variety of noninvasive methods, exploration geophysics allows scientists and engineers to investigate the shallow subsurface, revealing vital insights that impact various fields, from environmental studies to resource exploration. This article delve into the world of exploration geophysics of the shallow subsurface, its methods, applications, and significance.

Exploration geophysics is a branch of geophysics that focuses on characterizing subsurface properties without physical excavation. Instead, it relies on the measurement of physical properties of Earth materials and the use of geophysical techniques to interpret these properties. These techniques are instrumental in mapping and understanding subsurface structures, geological formations, and environmental conditions.

Methods of exploration geophysics for the shallow subsurface

Seismic refraction and reflection: Seismic waves generated at the surface are used to investigate subsurface structures. Refraction surveys determine depths and velocities of subsurface layers, while reflection surveys map the interfaces between different geological formations.

Ground Penetrating Radar (GPR): GPR utilizes radar pulses to image the subsurface. It's particularly useful for locating buried objects, mapping shallow bedrock, and assessing pavement thickness.

Electrical Resistivity Tomography (ERT): ERT measures the electrical resistivity of subsurface materials. It is effective in identifying changes in soil and groundwater properties, detecting contaminants, and characterizing aquifers.

Magnetic surveying: Magnetic surveys measure variations in the Earth's magnetic field caused by magnetic minerals in the subsurface. This method can help locate buried structures, map geological boundaries, and identify ore bodies.

Gravity surveying: Gravity surveys measure variations in gravitational acceleration. They are used to map subsurface density variations, such as those related to geological structures or groundwater resources.

Applications of exploration geophysics in the shallow subsurface

Environmental studies: Exploration geophysics plays a critical role in environmental investigations, helping to detect and characterize contaminants, assess groundwater resources, and monitor landfills and waste disposal sites.

Civil engineering: Engineers use geophysical surveys to evaluate the stability of construction sites, assess soil conditions, and determine foundation suitability for structures.

Resource exploration: Exploration geophysics aids in the discovery of natural resources such as groundwater, minerals, and hydrocarbons. It is essential for locating reserves and planning extraction.

Archaeology: Archaeologists use geophysical techniques to map buried archaeological features, such as ancient structures or artifacts, without excavation.

Infrastructure assessment: Geophysics helps assess the condition of critical infrastructure, such as roads, bridges, and pipelines, to ensure safety and prevent failures.

Significance and benefits

Exploration geophysics of the shallow subsurface offers several key benefits and significance.

Non-invasive: Geophysical methods are non-invasive and do not require physical disturbance of the ground, making them environmentally friendly and cost-effective.

Rapid surveys: Geophysical surveys can cover large areas relatively quickly, providing valuable information for decisionmaking in various applications.

Risk reduction: In environmental and engineering projects, geophysics helps identify potential hazards, reducing risks associated with construction or contamination.

Resource efficiency: Geophysical surveys assist in optimizing resource exploration, ensuring that valuable resources are located and extracted efficiently.

Scientific insights: Exploration geophysics contributes to scientific research by providing data that enhances our understanding of geological processes and subsurface dynamics.

Challenges and future directions

Despite its many advantages, exploration geophysics faces challenges.

Data interpretation: Accurate interpretation of geophysical data requires expertise and may be influenced by site-specific conditions.

Resolution limits: The resolution of geophysical surveys may not be sufficient for very shallow features or fine-scale structures.

Site accessibility: Some sites may be difficult to access for surveying, particularly in urban areas.

Future directions in exploration geophysics including, ongoing development of advanced geophysical techniques, such as 3D modeling and machine learning, enhances the accuracy and resolution of subsurface imaging. Geophysics will continue to play a crucial role in environmental monitoring and the assessment of climate change impacts on the subsurface. As resource demands increase, exploration geophysics will be vital in locating and managing water, minerals, and energy resources.

Exploration geophysics of the shallow subsurface is a versatile and essential tool that allows us to investigate the Earth beneath our feet without disturbing its delicate balance. Whether for environmental protection, resource exploration, civil engineering, or scientific research, the applications of exploration geophysics are vast and impactful. As technology advances and our understanding of subsurface processes deepens, exploration geophysics will continue to reveal the Earth's hidden secrets and contribute to sustainable and informed decision-making in various domains.