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The Basic Vocabulary of Geophysics

Here is a simple geophysical glossary of technical terms that we use on our website. It provides easy-to-understand definitions of the leading scientific terms you will see mentioned. Please use this page as a mini dictionary for words that are often used in the world of hydrologists and geophysicists.

Artificial Recharge:

Groundwater levels are reducing worldwide. Artificial recharge is a groundwater management technique used to replenish or recharge aquifers with water in a deliberate and controlled manner. This process involves human intervention, such as adding water to underground aquifers through various methods to increase groundwater levels or maintain the quality and quantity of groundwater resources.


When a water-bearing rock readily transmits water to wells and springs, it is called an aquifer – an underground layer of water-bearing, permeable rock, rock fractures, or consolidated materials. An aquifer is a body of porous rock or sediment saturated with groundwater. Groundwater enters an aquifer as precipitation seeps through the soil. It can move through the aquifer and resurface through springs and wells. An aquifer acts as a groundwater reservoir when the underlying rock is impermeable and is in the “saturated zone” of the Earth’s crust, where credible spaces are filled with water. A serious environmental problem arises when the aquifer is contaminated by sewage seepage or toxins from waste dumps. Saltwater can seep into the aquifer if the groundwater in coastal areas is over-exploited.

Aquifer Storage and Recovery:

Aquifer storage and recovery have been used for water resource management for hundreds of years. It is an active method for storing water underground during wet periods and recovering when needed, usually during dry periods. The technique is being further developed and refined as demand for fresh water threatens to exceed supply in many other parts of the world. Natural stores in the ground can be positioned up to hundreds of meters deep, depending on the type of subsoil; these systems, the naturally occurring groundwater and sediment at these depths are used as storage and heat transfer mediums.

Aquifer Vulnerability:

Groundwater vulnerability maps are still being developed or are rarely attempted worldwide, even though aquifer vulnerability methods are well-tested. Aquifer vulnerability is not an absolute characteristic but indicates where contamination will probably impact water quality. It is a method to predict the risk associated with such an aquifer and the overlying beds’ capacity to filter contaminants released from the surface.


Beneath the surface materials, gravel and soil, bedrock is found. Bedrock is a designation that covers, for example, limestone, sandstone, and granite that can extend hundreds of meters below the surface of the Earth toward the base of the Earth’s crust. BedroCrust is a solid and tightly bound consolidated rock, and by determining the specific type of bedrock, the region’s natural history can be described and mapped out.

Bias-Free Gate:

This term is related to the time window during which the tTEM system collects data from the subsurface. This “gate” is “bias-free,” implying that the data collected in this period is not influenced or distorted by external factors or the transmitter itself, allowing for a more accurate representation of the subsurface properties. The early bias-free gate in this tTEM system is crucial for obtaining high-resolution, reliable data for analyzing and studying the subsurface, particularly the top 30-50 meters critical for several applications like water supply, farming, construction, etc.

Depth of Investigation:

The depth of investigation is a critical parameter in subsurface studies, helping to determine the suitability of various methods for specific applications. It informs decisions on site characterization, groundwater assessment, resource exploration, and environmental remediation, ensuring that investigations are conducted effectively and yield meaningful results at the desired depths.


This is the phenomenon of the interaction of electric currents or fields and magnetic fields the interaction of electric and magnetic fields, and it encompasses a wide range of phenomena and applications in physics, engineering, and technology. Electromagnetic waves are a fundamental aspect of this field, including phenomena like electricity, magnetism, and electromagnetic radiation.

Hydrogeologic Models:

Hydrogeologic models play a critical role in managing groundwater resources, evaluating the potential impact of land use changes, designing healthy fields, and assessing the environmental effects of groundwater contamination. They provide valuable insights into subsurface water systems and help guide water resource management and ecological protection decision-making. These models are used to simulate and analyze the movement of groundwater, the distribution of subsurface water, and the interaction between groundwater and surface water. They are essential hydrogeology, environmental science, and water resource management tools.


One of the Earth’s most critical natural resources is groundwater, vital in supporting ecosystems, providing drinking water, and sustaining various human activities, including agriculture and industry. Sustainable practices, aquifer protection, and water quality monitoring are essential for effective groundwater resource management.

Geological Mapping:

Various methods are used in the geoscience landscape. Geological mapping is a fundamental method geologists and earth scientists use to visually represent the distribution, nature, and relationships of geological features and rock formations on the Earth’s surface and in subsurface regions. This mapping process involves fieldwork, data collection, and the creation of geological maps.

Near-Surface Mapping:

One crucial aspect of our work at TEMcompany and in the geological and geotechnical fields is creating images of the underground surface down to a few hundred meters using new surface imaging tools. Near-surface mapping involves studying and mapping geological features, subsurface structures, and other phenomena in the Earth’s uppermost layers. This mapping type is essential for various applications, including environmental studies, civil engineering projects, geotechnical investigations, and resource exploration.


Many of these technical terms cover concepts such as resistivity, also known as electrical resistivity tomography (ERT). This is a geophysical method used to investigate the subsurface properties of the Earth by measuring the electrical resistivity of geological materials. Resistivity geophysics is a versatile and noninvasive technique that provides valuable subsurface information for various applications. It is often used in combination with other geophysical methods to gain a comprehensive understanding of subsurface conditions.

Shallow Subsurface:

The Earth has several distinct layers, each with unique properties, composition, and characteristics. The shallow subsurface refers to the uppermost layers of the crust, which extend from the surface down to a relatively limited depth. This depth range can vary but typically encompasses the top few meters to several tens of meters below the ground surface. The shallow subsurface is a crucial geological zone with various characteristics and importance, and it plays a significant role in a wide range of environmental, geological, and engineering applications.

Subsurface Geology:

There are various branches of geoscience, and subsurface geology focuses on studying the geological features, materials, and structures beneath the Earth’s surface. It involves investigating the composition, properties, and history of rocks, sediments, and other subsurface materials and understanding the processes that have shaped the Earth’s subsurface over geological time scales. Subsurface geology is essential for various applications, including resource exploration, environmental assessment, civil engineering, and understanding the Earth’s geological history.

Subsurface Imaging:

When imaging an object below the surface of a medium, such as soil, water, atmosphere, or tissue, the technique is called subsurface imaging. It is an essential tool in various scientific, engineering, and environmental applications, allowing researchers and professionals to provide valuable information for scientific research, resource exploration, environmental management, and engineering applications. These insights into the subsurface are helping to make informed decisions and mitigate risks associated with subsurface conditions.

Subsurface Layers:

There are various geological and geophysical zones or strata that exist beneath the Earth’s surface, which are referred to in different contexts: These are the subsurface layers, which extend from the surface down to significant depths, and they play a crucial role in geological processes, resource exploration, environmental studies, and engineering applications.


Our name, business, and basis of existence are founded upon this method. The Transient Electromagnetic (TEM) system is a geophysical method used to investigate subsurface properties and structures by measuring the Earth’s electromagnetic response to a transient electromagnetic pulse. It is particularly useful for mapping the resistivity distribution in the subsurface, which can provide valuable information about geological formations and, most importantly, groundwater resources.

Transmitter Moment:

A key parameter in geophysics is the transmitter moment. It most commonly refers to the product of the transmitter current and the transmitter loop area in a controlled-source electromagnetic (CSEM) or electromagnetic induction survey. The transmitter moment is often used to characterize the electromagnetic source in such surveys and influences the quality and resolution of subsurface data obtained through electromagnetic methods like CSEM and electromagnetic induction.

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