earth science

Tidal triggering of earthquakes

Tidal triggering of earthquakes is a earth science 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 Tidal triggering of earthquakes rather than just read about it. In short: Tidal triggering of earthquakes is the idea that tidal forces may induce seismicity. In connection with earthquakes, syzygy refers to the idea that the combined tidal effects of the sun and moon – either directly as earth tides in the crust itself, or indirectly by hydrostatic loading due to ocean tides – should be able to trigger earthquakes in rock that is already stressed to the point of fracturing, and therefore…

Key takeaways

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

Reference excerpt

Tidal triggering of earthquakes is the idea that tidal forces may induce seismicity. In connection with earthquakes, syzygy refers to the idea that the combined tidal effects of the sun and moon – either directly as earth tides in the crust itself, or indirectly by hydrostatic loading due to ocean tides – should be able to trigger earthquakes in rock that is already stressed to the point of fracturing, and therefore a higher proportion of earthquakes should occur at times of maximal tidal stress, such as at the new and full moons. Scientists have searched for such a correlation for over a century, but with the exception of volcanic areas (including mid-ocean spreading ridges) the results have been mixed. It has been suggested that some negative results are due to failure to account for tidal phase and fault orientation (dip), while "many studies reporting positive correlations suffer from a lack of statistical rigor." One systematic investigation found "no evidence for an increase in seismicity during intervals of large tidal range but there is clear evidence for small but significant increase in earthquake rates near low tide"; it did not find an increase of earthquakes near peak spring tides. Seismicity is favored at low tides, particularly for reverse faults, because unloading unclamps the fault, reducing friction. Ocean loading has no effect at all on strike-slip faults. Research work has shown a robust correlation between small tidally induced forces and non-volcanic tremor activity. Volcanologists use the regular, predictable Earth tide movements to calibrate and test sensitive volcano deformation monitoring instruments. The tides may also trigger volcanic events.

See also Earthquake prediction#1990: New Madrid, U.S. (Browning) Jim Berkland#Methodology Love number Tidal effect on plate tectonics

Notes

Sources

Illustrations

Worked examples

Example 1 — a first encounter with Tidal triggering of earthquakes

Start with the simplest possible case. Write down what Tidal triggering of earthquakes claims or describes in one sentence, then invent the smallest concrete situation in which that sentence is true. In earth science, 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 Tidal triggering of earthquakes 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 Tidal triggering of earthquakes 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 Tidal triggering of earthquakes

In research: Tidal triggering of earthquakes appears in earth science 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 Tidal triggering of earthquakes 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: Tidal triggering of earthquakes is common in secondary-school and first-year university syllabi. It links to neighbouring topics Seismology stubs, Tides, Types of earthquake, so understanding it makes those chapters shorter.
In everyday life: Look for Tidal triggering of earthquakes 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 Tidal triggering of earthquakes in 20 minutes

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

Frequently asked questions

What is Tidal triggering of earthquakes in simple terms?

Why does Tidal triggering of earthquakes matter?

Because it connects several earth science 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 Tidal triggering of earthquakes?

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 Tidal triggering of earthquakes.