Seismic imaging uses energy waves to investigate physical features beneath the earth’s surface, with various techniques such as electrical resistivity tomography and ground-penetrating radar. The information is processed using tomographic reconstruction software algorithms to create a definitive picture of what lies beneath. Seismic imaging has practical applications in construction, mining, and geological analysis.
Seismic imaging is the process of investigating physical features beneath the surface of the earth. The technique, also known as geophysical imaging, uses the process of revealing sections of the Earth with an energy wave. In order for a researcher to take a seismic image, a geophysical tomograph must be used. The image is referred to as a tomogram. Since seismic imaging is considered an applied science, the information gleaned through the procedure generally has a practical use.
The task of taking a geophysical image uses projection tomographs from multiple directions. Each of these corners takes a slice of the Earth’s appearance and feeds the data into some sort of processor. Modern techniques use a computer to process the seismic image using tomographic reconstruction software algorithms, essentially placing each slice into one large image. This presents a definitive picture of what lies beneath the earth’s surface.
One of the most common forms of seismic imaging is known as electrical resistivity tomography. Electrical measurements are taken from the surface by drilling holes in the ground and placing electrodes inside. The method uses a direct current which creates an image from the information.
Ground-penetrating radar is also a popular technique for analyzing geophysical information below the surface. This method sends radar pulses into the ground and reflects signals from various structures in the ground. Usually the UHF or VHF frequencies of the radio spectrum are used. This is a non-invasive method of detecting various things like rocks, structures, openings, and water.
The best way to isolate metallic materials such as minerals below the surface is the concept of induced polarization. Similar to electrical resistivity tomography, an electric current is sent into the ground and monitored via electrodes to identify the voltage. The different resistive frequencies can be measured in a specific time interval. Unlike the other method, however, alternating current is used to provide the seismic image.
Reflection seismology is another form of performing seismic imaging. This allows researchers to send controlled seismic energy to the Earth’s surface using specialized vibration tools. Once the wave is reflected off an object, it travels back to a receiver, giving the analyst an understanding of the exact depth of the feature in question.
Seismic imaging has several applications. When engineers are trying to construct a building, the presence of underground objects must be ascertained. Additionally, mineral and petroleum mining uses the techniques to help locate resources. The practice is also used for general geological analysis in an attempt to study subsurface characteristics.
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