physics

Kiyoo Mogi

Kiyoo Mogi 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 Kiyoo Mogi rather than just read about it. In short: Kiyoo Mogi (茂木清夫, Mogi Kiyoo; 1929 in Yamagata Prefecture, Japan–6 June 2021) was a prominent seismologist. He was regarded as Japan's foremost authority on earthquake prediction and was a chair of the Japanese Coordinating Committee for Earthquake Prediction (CCEP).

Key takeaways

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

Reference excerpt

Kiyoo Mogi (茂木清夫, Mogi Kiyoo; 1929 in Yamagata Prefecture, Japan–6 June 2021) was a prominent seismologist. He was regarded as Japan's foremost authority on earthquake prediction and was a chair of the Japanese Coordinating Committee for Earthquake Prediction (CCEP). Mogi was also a director of the University of Tokyo's Earthquake Research Institute, a professor at Nihon University and a professor emeritus at Tokyo University. Due to the seismic activity in Japan, Mogi also took an interest in the safety of nuclear power in Japan. In 1969, Mogi predicted that there was a possibility of a shallow magnitude 8.0 earthquake in the Tōkai region of Japan, an area that has experienced a number of previous large earthquakes. Following the passing of the Large-Scale Earthquake Countermeasure Act, in 1978, Mogi was appointed to the newly created Earthquake Assessment Committee (EAC) for the expected Tokai earthquake, charged with warning the government if the quake was imminent. He went on to chair the ECA from 1991 until he resigned from the post in 1996 after failing to persuade the government of the need to take uncertainty into account when issuing warnings.

Nuclear power Following damage at the Kashiwazaki-Kariwa Nuclear Power Plant due to the 2007 Chūetsu offshore earthquake, Mogi called for the immediate closure of the Hamaoka Nuclear Power Plant, which was built close to the centre of the expected Tōkai earthquake despite his 1969 prediction. Previously, in 2004, he had stated that the issue 'is a critical problem which can bring a catastrophe to Japan through a man-made disaster'.

Mogi doughnut hypothesis In 1969, Mogi proposed a hypothesis for earthquake prediction, now known as the 'Mogi doughnut hypothesis', that major earthquakes tend to occur in an unusually seismically calm area surrounded by a ring of unusually high seismic activity. The Mogi doughnut is one of several pattern hypotheses that have been proposed.

Mogi model

In 1958, Mogi was responsible for a major advance in understanding the dynamics of volcanos. After studying data from several sources, he concluded that a mathematical solution developed by Yamakawa in 1955 could be used in the modelling of the deformation of a volcano caused by pressure changes in its magma chamber. The 'Mogi model' (also known as the 'Mogi-Yamakawa model') subsequently became the first commonly used quantitative method in volcanology, and is still widely used today.

Bibliography Experimental Rock Mechanics (2006) Earthquake Prediction (1985)

Worked examples

Example 1 — a first encounter with Kiyoo Mogi

Start with the simplest possible case. Write down what Kiyoo Mogi 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 Kiyoo Mogi 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 Kiyoo Mogi 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 Kiyoo Mogi

In research: Kiyoo Mogi 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 Kiyoo Mogi 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: Kiyoo Mogi is common in secondary-school and first-year university syllabi. It links to neighbouring topics 1929 births, 2021 deaths, Japanese seismologists, so understanding it makes those chapters shorter.
In everyday life: Look for Kiyoo Mogi 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 Kiyoo Mogi in 20 minutes

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

Frequently asked questions

What is Kiyoo Mogi in simple terms?

Why does Kiyoo Mogi 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 Kiyoo Mogi?

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 Kiyoo Mogi.