physics

Geophysical imaging

Geophysical imaging is a physics topic covered in the lgStudy science library. This page brings together a partial reference excerpt, illustrations, worked examples, real-world applications and a short study plan, so you can understand Geophysical imaging rather than just read about it. In short: Geophysical imaging (also known as geophysical tomography) is a minimally destructive geophysical technique that investigates the subsurface of a terrestrial planet. Geophysical imaging is a noninvasive imaging technique with a high parametrical and spatio-temporal resolution.

Key takeaways

Geophysical imaging belongs to physics; place it in that map before memorising details.
Learn the definition first, then one example that makes the definition concrete.
Connect Geophysical imaging to a quantity you can measure, compute or draw — that is where exam questions come from.
Reproduce the core statement of Geophysical imaging from memory before moving on to harder problems.

Reference excerpt

Geophysical imaging (also known as geophysical tomography) is a minimally destructive geophysical technique that investigates the subsurface of a terrestrial planet. Geophysical imaging is a noninvasive imaging technique with a high parametrical and spatio-temporal resolution. It can be used to model a surface or object understudy in 2D or 3D as well as monitor changes. There are many applications of geophysical imaging some of which include imaging the lithosphere and imaging glaciers. Many different techniques exist to perform geophysical imaging including seismic methods, electrical resistivity tomography, ground-penetrating radar, etc. Types of geophysical imaging:

Electrical resistivity tomography Ground-penetrating radar Induced polarization Seismic tomography and Reflection seismology Magnetotellurics

Applications

Imaging the Lithosphere Some geophysical imaging techniques for the Earth's lithosphere and upper mantle include teleseismic tomography, surface-wave tomography, gravity modeling, and electromagnetic methods. Geophysical imaging techniques can be combined to create a more accurate image of the lithosphere. The techniques used to image the lithosphere can be used to map out the thermostructure of the Earth. In turn, the thermostructure reveals near surface processes such as seismicity, magma emplacement, and mineralization events. The ability to image the thermostructure could also reveal geophysical observables like gravity and information about tectonic plates like plate velocity and strain partitioning.

Alpine Rock Glaciers Geophysical imaging techniques have been applied to alpine rock glaciers to better understand mountain permafrost and perform hazard-mitigation measures. The types of geophysical imaging used include: diffusive electromagnetic, geoelectric, seismic tomography, and ground-penetrating radar. In fact, the first use of ground-penetrating radar was to determine a glacier's depth in 1929. Two dimensional geophysical imaging techniques have recently allowed for 2D imaging of mountain permafrost.

Types of geophysical imaging

Seismic Methods Seismic methods utilize elastic energy created by natural and artificial sources to create an image of the subsurface. Seismic waves are recorded on geophones. Seismic methods are split up into three different methods, reflection, refraction, and surface wave, based on the physical property of the waves being considered. The reflection method looks at reflected energy from sharp boundaries to determine contrasts in density and velocity. Reflections methods are mainly applied in the upper subsurface; however, strong lateral and vertical seismic velocity variations cause reflection methods to be difficult to implement in the upper 50 meters of the subsurface. The refraction method looks at refracted compressional, p-waves, or shear, s-waves, that bend through velocity gradients. Tracking differences in velocity of the p-waves and s-waves can be useful because s-wave's velocity react differently to fluid saturation and fracture geometry. Reflection and refraction seismic methods exploit the waves that can be produced by sledgehammer, explosives, weight drops, and vibrators to image the subsurface. The third seismic method, surface wave methods, look at the surface waves that seem to roll along the surface (ground roll). Utilization of several different seismic methods can accomplish a more precise and clearer result of seismic imaging.

See also Archaeological geophysics Electrical resistivity tomography Ground-penetrating radar Exploration geophysics Geophysical Tomography Group (The) Medical imaging Stanford Exploration Project

References

Illustrations

Worked examples

Example 1 — a first encounter with Geophysical imaging

Start with the simplest possible case. Write down what Geophysical imaging claims or describes in one sentence, then invent the smallest concrete situation in which that sentence is true. In physics, the smallest case is usually a single object, a single equation or a single measurement. Check that every symbol or term in your sentence has a meaning in that case.

Example 2 — changing one variable

Take the situation from Example 1 and change exactly one quantity: double it, halve it, or set it to zero. Predict what should happen to Geophysical imaging before you calculate. Comparing your prediction with the result is the fastest way to find out whether you understand the idea or only the words.

Example 3 — an exam-style question

Typical questions about Geophysical imaging ask you to (a) state it precisely, (b) apply it to given data, and (c) explain a limitation. Practise writing all three answers in under five minutes; the third part is what separates a full-mark answer from an average one.

Applications of Geophysical imaging

In research: Geophysical imaging appears in physics research whenever the underlying quantities have to be modelled precisely. Papers usually cite it as a starting assumption and then explore where it breaks down.
In technology and industry: Engineering practice reuses Geophysical imaging in design rules, simulations and safety margins. Knowing the idea lets you read a specification sheet and understand why the numbers look the way they do.
In the classroom: Geophysical imaging is common in secondary-school and first-year university syllabi. It links to neighbouring topics Geophysical imaging, so understanding it makes those chapters shorter.
In everyday life: Look for Geophysical imaging outside the textbook — in sport, cooking, traffic, electronics or the sky above you. An example you found yourself is remembered far longer than one you were given.

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How to study Geophysical imaging in 20 minutes

Read the reference excerpt below once, without taking notes.
Close the page and write down what Geophysical imaging means in your own words.
Compare your version with the excerpt and mark what you missed.
Work through the three examples above with pen and paper.
Explain Geophysical imaging out loud to somebody else — or to Teacher Smith in the lgStudy chat.

Frequently asked questions

What is Geophysical imaging in simple terms?

Why does Geophysical imaging matter?

Because it connects several physics ideas at once: it gives you a definition you can apply, a quantity you can calculate, and a way to check whether a result is plausible.

How should I study Geophysical imaging?

Read the excerpt, restate it from memory, then work through the examples and applications listed on this page. The five-step study plan above takes about twenty minutes.

What does this page cover?

It gives you a compact reference excerpt plus original lgStudy explanations, examples, applications and study material on Geophysical imaging.