seismo-electromagnetics
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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 Earthquake prediction is a branch of the science of seismology concerned with the specification of the time, location, and magnitude of future earthquakes within stated limits, and particularly "the determination of parameters for the ''next'' ...
. 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 Parkfield earthquake is a name given to various large earthquakes that occurred in the vicinity of the town of Parkfield, California, United States. The San Andreas fault runs through this town, and six successive magnitude 6 earthquakes occurre ...
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 A van is a type of road vehicle used for transporting goods or people. Depending on the type of van, it can be bigger or smaller than a pickup truck and SUV, and bigger than a common car. There is some varying in the scope of the word across th ...
– 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.twenty articles in a special issue of
Geophysical Research Letters ''Geophysical Research Letters'' is a biweekly peer-reviewed scientific journal of geoscience published by the American Geophysical Union that was established in 1974. The editor-in-chief is Harihar Rajaram. Aims and scope The journal aims for rap ...

table of contents
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 Noise is unwanted sound considered unpleasant, loud or disruptive to hearing. From a physics standpoint, there is no distinction between noise and desired sound, as both are vibrations through a medium, such as air or water. The difference aris ...
and relate them to a possible impending earthquake. In case of verification (classification as "SES activity"),
natural time analysis Natural time analysis is a statistical method applied to analyze complex time series and critical phenomena, based on event counts as a measure of "time" rather than the clock time.Varotsos, Sarlis & Skordas 2011 (book), preface and chapter 2 Nat ...
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 () 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."


QuakeFinder and 'Freund physics'

In his investigations of crystalline physics, 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 battery currents 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 "Freund physics". Most seismologists reject Freund's suggestion that stress-generated signals can be detected and put to use as precursors, for a number of reasons. First, it is believed 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 have extensively searched for statistically reliable electrical precursors, using sophisticated instrumentation, and have not identified any such precursors. And thirdly, water in the earth's crust would cause any generated currents to be absorbed before reaching the surface. QuakeFinder is a company focused on developing a system for
earthquake prediction Earthquake prediction is a branch of the science of seismology concerned with the specification of the time, location, and magnitude of future earthquakes within stated limits, and particularly "the determination of parameters for the ''next'' ...
. The company has a long-standing collaboration with Freund. They have deployed a network of sensor stations that detect the electromagnetic pulses the team believes precede major earthquakes. Each sensor is believed to have a range of approximately 10 miles (16 km) from the instrument to the source of the pulses. As of 2016, the company says they have 125 stations in California, and their affiliate Jorge Heraud says he has 10 sites in Peru. Using these sensors, Heraud says that he has been able to triangulate pulses seen from multiple sites, in order to determine the origin of the pulses. He said that the pulses are seen beginning from 11 to 18 days before an impending earthquake, and have been 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 Heraud have yet verifiably predicted an earthquake, much less issued multiple predictions of the type that might be objectively testable for statistical significance. Current research suggests it's dissolved gases that come out of solution when de-pressurized and then ionize to generate the electrical signatures.


Corralitos anomaly

In the month prior to the
1989 Loma Prieta earthquake The 1989 Loma Prieta earthquake occurred on California's Central Coast on October 17 at local time. The shock was centered in The Forest of Nisene Marks State Park in Santa Cruz County, approximately northeast of Santa Cruz on a section of t ...
measurements of the earth's magnetic field at ultra-low frequencies by a
magnetometer A magnetometer is a device that measures magnetic field or magnetic dipole moment. Different types of magnetometers measure the direction, strength, or relative change of a magnetic field at a particular location. A compass is one such device, ...
in Corralitos, California, just 7 km from the epicenter of the impending earthquake, started showing anomalous increases in amplitude. Just three hours before the quake the measurements soared to about thirty times greater than normal, with amplitudes tapering off after the quake. Such amplitudes had not been seen in two years of operation, nor in a similar instrument located 54 km away. To many people such apparent locality in time and space suggested an association with the earthquake. Additional magnetometers were subsequently deployed across northern and southern California, but after ten years, and several large earthquakes, similar signals have not been observed. More recent studies have cast doubt on the connection, attributing the Corralitos signals to either unrelated magnetic disturbance or, even more simply, to sensor-system malfunction. Study of the closely monitored 2004 Parkfield earthquake found no evidence of precursory electromagnetic signals of any type.


ULF magnetic field precursors

Two recent studies by Konstantinos Eftaxias and his colleagues examined
ULF Ulf, or Ulv is a masculine name common in Scandinavia and Germany. It derives from the Old Norse word for " wolf" (''úlfr'', see Wulf). The oldest written record of the name's occurrence in Sweden is from a runestone of the 11th century. The ...
magnetic fields preceding major earthquakes. At the
2011 Tohoku earthquake Eleven or 11 may refer to: *11 (number), the natural number following 10 and preceding 12 * one of the years 11 BC, AD 11, 1911, 2011, or any year ending in 11 Literature * ''Eleven'' (novel), a 2006 novel by British author David Llewellyn *''E ...
, ULF radiation exhibited critical behavior, while at the 2008 Sichuan earthquake, the researchers found a depression of the horizontal ULF magnetic field, which may also be interpreted as a manifestation of criticality.


TEC variations

Professor Kosuke Heki of
Hokkaido University , or , is a Japanese national university in Sapporo, Hokkaido. It was the fifth Imperial University in Japan, which were established to be the nation's finest institutions of higher education or research. Hokkaido University is considered ...
in
Japan Japan ( ja, 日本, or , and formally , ''Nihonkoku'') is an island country in East Asia. It is situated in the northwest Pacific Ocean, and is bordered on the west by the Sea of Japan, while extending from the Sea of Okhotsk in the n ...
said that he discovered by accident that GPS signals changed about 40 minutes before the 2011 Tohoku-Oki earthquake. Reviewing historical data for other earthquakes, he found that this same correlation occurred during other incidents. He suggested that the GPS signals were detecting variations in the levels of the TEC (total electron content) of the ionosphere in the hour preceding an earthquake.


Satellite observations

The "Detection of Electro-Magnetic Emissions Transmitted from Earthquake Regions" satellite, constructed by
CNES The (CNES; French: ''Centre national d'études spatiales'') is the French government space agency (administratively, a "public administration with industrial and commercial purpose"). Its headquarters are located in central Paris and it is und ...
, has made observations which show strong correlations between certain types of low frequency electromagnetic activity and the most seismically active zones on the Earth, and have shown a sharp signal in the
ionospheric The ionosphere () is the ionized part of the upper atmosphere of Earth, from about to above sea level, a region that includes the thermosphere and parts of the mesosphere and exosphere. The ionosphere is ionized by solar radiation. It plays an ...
electron The electron ( or ) is a subatomic particle with a negative one elementary electric charge. Electrons belong to the first generation of the lepton particle family, and are generally thought to be elementary particles because they have n ...
density Density (volumetric mass density or specific mass) is the substance's mass per unit of volume. The symbol most often used for density is ''ρ'' (the lower case Greek letter rho), although the Latin letter ''D'' can also be used. Mathematicall ...
and
temperature Temperature is a physical quantity that expresses quantitatively the perceptions of hotness and coldness. Temperature is measured with a thermometer. Thermometers are calibrated in various temperature scales that historically have relied o ...
near southern Japan seven days before a 7.1 magnitude earthquake occurred there (on August 29 and September 5, 2004, respectively). Quakesat is an earth observation
nanosatellite A small satellite, miniaturized satellite, or smallsat is a satellite of low mass and size, usually under . While all such satellites can be referred to as "small", different classifications are used to categorize them based on mass. Satellites ca ...
based on 3
CubeSat A CubeSat is a class of miniaturized satellite based around a form factor consisting of cubes. CubeSats have a mass of no more than per unit, and often use commercial off-the-shelf (COTS) components for their electronics and structure. CubeSats ...
s. It was designed to be a proof-of-concept for collecting
extremely low frequency Extremely low frequency (ELF) is the ITU designation for electromagnetic radiation (radio waves) with frequencies from 3 to 30  Hz, and corresponding wavelengths of 100,000 to 10,000 kilometers, respectively. In atmospheric scien ...
earthquake precursor signals from space. The primary instrument is a
magnetometer A magnetometer is a device that measures magnetic field or magnetic dipole moment. Different types of magnetometers measure the direction, strength, or relative change of a magnetic field at a particular location. A compass is one such device, ...
housed in a 2-foot (0.6 m) telescoping boom. The science behind the concept is disputed. ESPERIA is an equatorial space mission mainly concerned with detecting any tectonic and preseismic related signals. More in general, it has been proposed for defining the near-Earth electromagnetic, plasma, and particle environment, and for studying perturbations and instabilities in the ionosphere-
magnetosphere In astronomy and planetary science, a magnetosphere is a region of space surrounding an astronomical object in which charged particles are affected by that object's magnetic field. It is created by a celestial body with an active interior d ...
transition region. To study earthquake preparation processes and
anthropogenic Anthropogenic ("human" + "generating") is an adjective that may refer to: * Anthropogeny, the study of the origins of humanity Counterintuitively, anthropogenic may also refer to things that have been generated by humans, as follows: * Human i ...
impacts in the Earth's surface, a phase A study has been realized for the
Italian Space Agency The Italian Space Agency ( it, Agenzia Spaziale Italiana; ASI) is a government agency established in 1988 to fund, regulate and coordinate space exploration activities in Italy. The agency cooperates with numerous national and international enti ...
. The Deformation, Ecosystem Structure and Dynamics of Ice (DESDynI) radar satellite, which was canceled in the White House's 2012 budget proposal, would have the capacity to identify elastic strain in tectonic plates, combining
L-band The L band is the Institute of Electrical and Electronics Engineers (IEEE) designation for the range of frequencies in the radio spectrum from 1 to 2 gigahertz (GHz). This is at the top end of the ultra high frequency (UHF) band, at the lowe ...
interferometric Interferometry is a technique which uses the '' interference'' of superimposed waves to extract information. Interferometry typically uses electromagnetic waves and is an important investigative technique in the fields of astronomy, fiber o ...
synthetic aperture radar and a multi-beam infrared
lidar Lidar (, also LIDAR, or LiDAR; sometimes LADAR) is a method for determining ranges (variable distance) by targeting an object or a surface with a laser and measuring the time for the reflected light to return to the receiver. It can also be ...
to detect strains in the Earth's surface that could lead to serious earthquakes. Russia and the United Kingdom agreed to jointly deploy two satellites in 2015 that will measure electromagnetic signals that are released from the earth's crust prior to earthquakes. The project is said to be able to "help predict earthquakes and potentially save thousands of lives." Another site of current research is China, where a satellite launch was planned for 2014, to provide data from ionospheric phenomena for comparison with seismo-electromagnetic phenomena on the ground. Such a link is partially borne out in the current literature, with ionospheric phenomena already shown to precede seismic phenomena by a few hours to days. The network would potentially show whether such ionospheric phenomena are sourced from ground electrical phenomena.


See also

*
Electrical resistivity tomography Electrical resistivity tomography (ERT) or electrical resistivity imaging (ERI) is a geophysical technique for imaging sub-surface structures from electrical resistivity measurements made at the surface, or by electrodes in one or more borehole ...
* Induced polarization *
Magnetometer A magnetometer is a device that measures magnetic field or magnetic dipole moment. Different types of magnetometers measure the direction, strength, or relative change of a magnetic field at a particular location. A compass is one such device, ...
* Seismoelectrical method * Telluric current *
VAN method A van is a type of road vehicle used for transporting goods or people. Depending on the type of van, it can be bigger or smaller than a pickup truck and SUV, and bigger than a common car. There is some varying in the scope of the word across th ...


References


Sources

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Further reading

*Seismo electromagnetics: lithosphere-atmosphere-ionosphere coupling, Masashi Hayakawa, Oleg A. Molchanov, TerraPub, 2002,
On the reported magnetic precursor of the 1989 Loma Prieta earthquake
Jeremy N. Thomas, Jeffrey J. Love, Malcolm J.S. Johnston, Phys. Earth Planet. Int., 173, 207–215, doi:10.1016/j.pepi.2008.11.014, 2009.
Ionospheric precursors of earthquakes
Sergey Pulinets, Kirill Boyarchuk, Springer, 2004, *Electromagnetic Phenomenon Related to Earthquakes and Volcanoes, Birbal Singh, Narosa Pub. House, 2008, 17 Jun 2009,
A Critical review of VAN: earthquake prediction from seismic electrical signals
James Lighthill, World Scientific, 1996, {{ISBN, 978-981-02-2542-1
Monitoring of ULF (ultra-low-frequency) Geomagnetic Variations Associated with Earthquakes
Masashi Hayakawa, Katsumi Hattori and Kenji Ohta, Sensors 2007, 7, 1108–1122
Pre-earthquake ionospheric anomalies registered by continuous GPS TEC measurements
J. Y. Liu, Y. J. Chuo, S. J. Shan, Y. B. Tsai, Y. I. Chen, S. A. Pulinets, and S. B. Yu, Annales Geophysicae (2004) 22: 1585–1593 Geomagnetism Seismology