astronomy

Preliminary reference Earth model

Preliminary reference Earth model is a astronomy 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 Preliminary reference Earth model rather than just read about it. In short: The preliminary reference Earth model (PREM) plots the average of Earth's properties by depth. It includes a table of Earth properties, including elastic properties, attenuation, density, pressure, and gravity.

Key takeaways

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

Reference excerpt

The preliminary reference Earth model (PREM) plots the average of Earth's properties by depth. It includes a table of Earth properties, including elastic properties, attenuation, density, pressure, and gravity. PREM has been widely used as the basis for seismic tomography and related global geophysical models. It incorporates anelastic dispersion and anisotropy and therefore it is frequency-dependent and transversely isotropic for the upper mantle. PREM was developed by Adam M. Dziewonski and Don L. Anderson in response to guidelines of a "Standard Earth Model Committee" of the International Association of Geodesy (IAG) and the International Association of Seismology and Physics of the Earth's Interior (IASPEI) Other Earth reference models include iasp91 and ak135.

References

External links IRIS EMC - Reference Earth Models Table of values in PREM model Model formulas, inputs, and overview

Illustrations

Worked examples

Example 1 — a first encounter with Preliminary reference Earth model

Start with the simplest possible case. Write down what Preliminary reference Earth model claims or describes in one sentence, then invent the smallest concrete situation in which that sentence is true. In astronomy, 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 Preliminary reference Earth model 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 Preliminary reference Earth model 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 Preliminary reference Earth model

In research: Preliminary reference Earth model appears in astronomy 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 Preliminary reference Earth model 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: Preliminary reference Earth model is common in secondary-school and first-year university syllabi. It links to neighbouring topics Planetary geology, Structure of the Earth, so understanding it makes those chapters shorter.
In everyday life: Look for Preliminary reference Earth model 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 Preliminary reference Earth model in 20 minutes

Read the reference excerpt below once, without taking notes.
Close the page and write down what Preliminary reference Earth model 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 Preliminary reference Earth model out loud to somebody else — or to Teacher Smith in the lgStudy chat.

Frequently asked questions

What is Preliminary reference Earth model in simple terms?

Why does Preliminary reference Earth model matter?

Because it connects several astronomy 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 Preliminary reference Earth model?

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 Preliminary reference Earth model.