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The Basic Vocabulary of Geophysics

Our vision is to be technology leader in seamlessly integrated hardware and software for subsurface imaging so we have created a simple, fundamental glossary for non-experts.

Here you’ll find a simple glossary of technical terms used in our web content – the glossary provides easy-to-understand definitions for the main scientific terms used on this website in the risk assessment domain. Please use this as a mini dictionary for words often used in the world of hydrologists and geophysicists. At TEMcompany the goal is that our specialized expertise, can be your go-to trusted advisor in the geophysical and TEM method jungle.


Artificial Recharge:

Across the world, groundwater levels are reducing. Artificial recharge is a groundwater management technique used to replenish or recharge aquifers with water in a deliberate and controlled manner. This process involves the human intervention of adding water to underground aquifers, typically 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 in 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 are in the “saturated zone” of the Earth’s crust, where all available spaces are filled with water. A serious environmental problem arises when the aquifer is contaminated by the seepage of sewage or toxins from waste dumps. If the groundwater in coastal areas is over-exploited, salt water can seep into the aquifer.

Aquifer Storage and Recovery:

For hundreds of years, the technique of aquifer storage and recovery has been used for water resource management. It is known as an active method for storing water underground during wet periods and for its recovery when needed, usually 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. With natural stores in the ground that can be positioned up to hundreds of meters depth, depending on the type of subsoil, these systems, the naturally occurring groundwater and sediment at these depths are used as storage and heat transfer medium.

Aquifer Vulnerability:

All over the world groundwater vulnerability maps are still undergoing development or are rarely attempted, even though aquifer vulnerability methods are well tested. Aquifer vulnerability is not an absolute characteristic but indicating where contamination probably will impact water quality and is a method to predict the risk associated with such an aquifer and the capacity of the overlying beds serving as a filter of contaminants released from the surface.


Beneath the surface materials gravel, and soil, the bedrock is found, which 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 Earth’s crust. Bedrock is solid and tightly bound consolidated rock, and by determining the specific type of bedrock the natural history of the region 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 that are 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 related to 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 and include 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 well fields, and assessing the environmental impact of groundwater contamination. They provide valuable insights into subsurface water systems and help guide decision-making in water resource management and environmental protection. 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 tools in hydrogeology, environmental science, and water resource management.


One of the Earth’s most important natural resources is groundwater, and our groundwater plays a vital role 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 components of effective groundwater resource management.

Geological Mapping:

There are various methods used in the geoscience landscape. Geological mapping is a fundamental method used by geologists and earth scientists 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 of the crucial fields of our work at TEMcompany and in the geological and geotechnical field is to create images of the underground surface down to a few hundred of meters using new surface imaging tools. Near-surface mapping refers to the process of studying and mapping geological features, subsurface structures, and other phenomena in the Earth’s uppermost layers. This type of mapping is essential for various applications, including environmental studies, civil engineering projects, geotechnical investigations, and resource exploration.


Many of these technical terms covers different concepts, such as resistivity that is 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 non-invasive 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 is composed of several distinct layers, each with its own unique properties, composition, and characteristics. The shallow subsurface refers to the uppermost layers of the Crust, extending 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 the one focusing on studying of the geological features, materials, and structures beneath the Earth’s surface is subsurface geology. 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 is 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 that is referred to in different context: These are the subsurface layers and 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 is founded upon this method. The Transient Electromagnetic (TEM) system is a geophysical method used to investigate subsurface properties and structures by measuring the electromagnetic response of the Earth 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 the geophysics world is the transmitter moment. 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. It 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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