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Seismo-electromagnetics

Seismo-electromagnetics 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 Seismo-electromagnetics rather than just read about it. In short: Seismo-electromagnetics are various electro-magnetic phenomena believed to be generated by tectonic forces acting on the Earth's crust, and possibly associated with seismic activity such as earthquakes and volcanoes. Study of these has been prompted by the prospect they might be generated by the increased stress leading up to an earthquake, and might thereby provide a basis for short-term earthquake prediction.

Key takeaways

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

Reference excerpt

Seismo-electromagnetics are various electro-magnetic phenomena believed to be generated by tectonic forces acting on the Earth's crust, and possibly associated with seismic activity such as earthquakes and volcanoes. Study of these has been prompted by the prospect they might be generated by the increased stress leading up to an earthquake, and might thereby provide a basis for short-term earthquake prediction. However, despite many studies, no form of seismo-electromagnetics has been shown to be effective for earthquake prediction. A key problem is that earthquakes themselves produce relatively weak electromagnetic phenomena, and the effects from any precursory phenomena are likely to be too weak to measure. Close monitoring of the Parkfield earthquake revealed no significant pre-seismic electromagnetic effects. However, some researchers remain optimistic, and searches for seismo-electromagnetic earthquake precursors continue.

VAN method The VAN method – named after P. Varotsos, K. Alexopoulos and K. Nomicos, authors of the 1981 papers describing it – measures low frequency electric signals, termed "seismic electric signals" (SES), by which Varotsos and several colleagues claimed to have successfully predicted earthquakes in Greece. Both the method itself and the manner by which successful predictions were claimed have been severely criticized and debated by VAN, but the critics have not retracted their views. Since 2001, the VAN group has introduced a concept they call "natural time", applied to the analysis of their precursors. Initially it is applied on SES to distinguish them from noise and relate them to a possible impending earthquake. In case of verification (classification as "SES activity"), natural time analysis is additionally applied to the general subsequent seismicity of the area associated with the SES activity, in order to improve the time parameter of the prediction. The method treats earthquake onset as a critical phenomenon. After 2006, VAN say that all alarms related to SES activity have been made public by posting at arxiv.org. One such report was posted on Feb. 1, 2008, two weeks before the largest earthquake in Greece during the period 1983–2011. This earthquake occurred on February 14, 2008, with magnitude (Mw) 6.9. VAN's report was also described in an article in the newspaper Ethnos on Feb. 10, 2008. However, Gerassimos Papadopolous complained that the VAN reports were confusing and ambiguous, and that "none of the claims for successful VAN predictions is justified", but this complaint was answered on the same issue.

QuakeFinder and Freund physics In his investigations of crystalline physics, Dr. Friedemann Freund found that water molecules embedded in rock can dissociate into ions if the rock is under intense stress. The resulting charge carriers can generate electrically charged particles under certain conditions. Freund suggested that perhaps these currents could be responsible for earthquake precursors such as electromagnetic radiation, earthquake lights and disturbances of the plasma in the ionosphere. The study of such currents and interactions is known as electromagnetic precursor energy signals or Freund physics. Most seismologists reject Dr. Freund's theory that stress-generated signals can be detected and put to use as precursors, for three reasons. First, it is theorized that stress does not accumulate rapidly before a major earthquake, and thus there is no reason to expect large currents to be rapidly generated. Secondly, seismologists searched for statistically reliable electrical precursors, using seven field test instruments prior to the 2004 Parkfield earthquake and did not identify any such precursors. And thirdly, it is theorized water in the earth's crust would cause any charged particles to be absorbed before reaching the surface. QuakeFinder was a company focused on developing a system for deploying magnetic field sensors (magnetometer) with a mission to save lives by forecasting earthquakes. The company operated as an independent company with controlling interest from Stellar Solutions, LLC and included a long-standing research collaboration between Mr. Tom Blier and Dr. Freund. The company deployed a network of sensor stations to detect low-frequency, electromagnetic pulses the team believed might precede major earthquakes. The sensors were reported to have a range of approximately 10 miles (16 km) from the instrument to the source of the pulses. As of 2016, the company reported 125 stations in California, and their research colleague, Dr. Jorge Heraud (Pontifica Universidad Catolica del Peru) reported 10 sites in Peru. Using these sensors, Dr. Heraud published peer-reviewed findings that he had been able to triangulate pulses seen from multiple sites, in order to determine the origin of the pulses. Dr. Heraud reported that the pulses were seen beginning from 11 to 18 days before an impending earthquake, and could be used to determine the location and timing of future seismic events. However, insofar as a verifiable prediction would require a publicly stated announcement of the location, time, and size of an impending event before its occurrence, neither QuakeFinder nor Dr. Heraud verifiably predicted an earthquake, nor issued multiple predictions of the type that might be objectively testable for statistical significance. Current research suggests the electrical signatures are produced by dissolved gases that come out of solution when de-pressurized and then ionize.

… excerpt ends here. Continue reading the full article.

Worked examples

Example 1 — a first encounter with Seismo-electromagnetics

Start with the simplest possible case. Write down what Seismo-electromagnetics 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 Seismo-electromagnetics 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 Seismo-electromagnetics 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 Seismo-electromagnetics

In research
Seismo-electromagnetics 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 Seismo-electromagnetics 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
Seismo-electromagnetics is common in secondary-school and first-year university syllabi. It links to neighbouring topics Geomagnetism, Seismology, so understanding it makes those chapters shorter.
In everyday life
Look for Seismo-electromagnetics 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 Seismo-electromagnetics in 20 minutes

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

Frequently asked questions

What is Seismo-electromagnetics in simple terms?

Seismo-electromagnetics are various electro-magnetic phenomena believed to be generated by tectonic forces acting on the Earth's crust, and possibly associated with seismic activity such as earthquakes and volcanoes. Study of these has been prompted by the prospect they might be generated by the in…

Why does Seismo-electromagnetics 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 Seismo-electromagnetics?

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 Seismo-electromagnetics.

Tags

  • Geomagnetism
  • Seismology

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