Microgravity Surveys

Microgravity surveying is a geophysical mapping technique that measures localised variations within the Earth's gravitational field to determine areas of contrasting density.

Microgravity surveying is commonly performed to aid in the location of buried features such as faults, sinkholes, tunnels, and voids associated with mines, quarries, and infrastructure. Data are acquired non-intrusively using the latest high-accuracy gravimeters. Gravimeters can be deployed across linear profiles and/or equally spaced grids at survey stations in varying increments, depending on the depth of investigation.

Gravity surveys are often used in conjunction with other geophysical techniques, such as ground-penetrating radar (GPR) and electrical resistivity tomography (ERT), to build up a more complete picture of the subsurface.

SEP Geophysical can carry out microgravity surveys with great precision. We make sure that the data quality is monitored constantly and that all corrections, modelling and data processing methods are done meticulously in order to obtain the most accurate results using this sensitive technique.

Microgravity Survey Applications

Mapping of variations in subsurface density

Geophysical surveys are used to map the three-dimensional density distribution of the subsurface. The gravity method is ideal for mapping subsurface density variations, which can be caused by a variety of geological processes.

Voiding, cavities and solution features

The microgravity method can be used to detect and map voids, cavities and solution features within the subsurface. These features often occur in karst terrain and can range in size from small fractures to large caverns.

Cave, Dene and Swallow Hole Detection

Karst terrain is characterised by the presence of caves, dolines (sinkholes) and swallow holes. The microgravity method can be used to map these features, as well as their subsurface extent.

Historic mine-workings

The microgravity geophysical method can be used in the assessment of the subsurface extent of historic mine workings. This is particularly useful in areas where there is no surface evidence of mining activity.

Geological Mapping including near-surface fault detection

The microgravity method can be used for geological mapping at a variety of scales. This includes the mapping of near-surface fault zones, which can be achieved by analysing variations in subsurface density.

Benefits of Microgravity Surveys

The microgravity method has a number of advantages over other types of ground investigations, including:

Non-intrusive – This method is non-intrusive and, therefore, causes no damage to the environment.

Precise – Gravimeters are capable of measuring very small variations in density, making them an ideal tool for mapping subtle features such as fractures and solution features.

Versatile – The method can be used in a variety of different settings and environments.

Microgravity Survey FAQs

How does a microgravity survey work?

A gravity survey works by taking surface measurements to determine changes in the earth's gravitational field caused by variations in subsurface density. This is achieved by using a highly sensitive instrument called a gravimeter, which are able to detect very small changes in gravity.

When a gravimeter is placed over a dense material, it measures a higher acceleration due to gravity, indicating a positive gravity anomaly. Conversely, when positioned above a less dense material, such as an air-filled cavity, the instrument detects a lower gravitational acceleration, signifying a negative gravity anomaly (relative gravity low).

By collecting multiple measurements across an area, a gravity map can be created to identify areas of density contrast and help detect subsurface features.

What are the limitations of a microgravity survey?

In comparison to some other geophysical methods, the main limitation of a microgravity survey is the time and attention to detail required to manage the sensitivity of the measurements. The microgravity measurements need to be taken very precisely and any measurement errors or inaccuracies can impact the results of the survey.

How much does a microgravity survey cost?

The cost of microgravity surveying will vary depending on a number of factors, including the size and complexity of the project, as well as the location and accessibility of the site. For an accurate quote, it is best to speak to one of our team.

What equipment is required for a microgravity survey?

A microgravity survey will require the use of a gravimeter, which is a sensitive instrument that measures changes in gravity. Additionally, you will need high-precision topographic equipment to accurately map the location of gravity measurements, such as a base station.

When is a gravity survey required?

It is often recommended that a microgravity survey is carried out prior to construction or development work, as this can help to identify any potential hazards or problems that may be present in the area. A microgravity survey can help to identify features such as voiding, caves and mine workings, which could cause safety issues if not addressed properly.

Additionally, this type of survey can be used in geological investigations to map; variations in competent material, and shallow igneous dykes.

Get in Touch

If you would like to find out more about microgravity surveys, or if you would like to speak to one of our team, please don't hesitate to get in touch. We are highly experienced in this area, and we would be more than happy to discuss your specific requirements.

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