Editing Earthquake prediction (section)

===== VAN seismic electric signals =====
{{Main|VAN method}}
<!-- NOTE TO EDITORS: this section is for describing electromagnetic anomalies as possible precursors. It is *not* the place for a critical assessment, or even a full description, of the VAN method, other than as relates to "SES", lest this section becomes bloated and out of proportion to the weight of the other sections. -->
The most touted, and most criticized, claim of an electromagnetic precursor is the [[VAN method]] of physics professors [[Panayiotis Varotsos]], Kessar Alexopoulos and Konstantine Nomicos (VAN) of the [[National and Capodistrian University of Athens|University of Athens]]. In a 1981 paper<ref>{{Harvnb|Varotsos|Alexopoulos|Nomicos|1981}}, described by {{Harvnb|Mulargia|Gasperini|1992|p=32}}, and {{Harvnb|Kagan|1997b|loc=§3.3.1|p=512}}.</ref> they claimed that by measuring geoelectric voltages – what they called "seismic electric signals" (SES) – they could predict earthquakes.{{efn|1=Over time the claim was modified. See [[#1983–1995: Greece (VAN)|1983–1995: Greece (VAN)]] for more details.}}

In 1984, they claimed there was a "one-to-one correspondence" between SES and earthquakes<ref>{{Harvnb|Varotsos|Alexopoulos|1984b|p=100}}.</ref> – that is, that "''every sizable EQ is preceded by an SES'' and inversely ''every SES is always followed by an EQ'' the magnitude and the [[epicenter]] of which can be reliably predicted"<ref>{{Harvnb|Varotsos|Alexopoulos|1984b|p=120}}. Italicization from the original.</ref> – the SES appearing between 6 and 115 hours before the earthquake. As proof of their method they claimed a series of successful predictions.<ref>{{Harvnb|Varotsos|Alexopoulos|1984b|loc=Table 3|p=117}}; {{Harvnb|Varotsos|Alexopoulos|Nomicos|Lazaridou|1986}}; {{Harvnb|Varotsos|Lazaridou|1991|loc=Table 3|p=341}}; {{Harvnb|Varotsos|Lazaridou|Eftaxias|Antonopoulos|1996a|loc=Table 3|p=55}}. These are examined in more detail in [[#1983–1995: Greece (VAN)|1983–1995: Greece (VAN)]].</ref>

Although their report was "saluted by some as a major breakthrough",{{efn|1=One enthusiastic supporter (Uyeda) was reported as saying "VAN is the biggest invention since the time of Archimedes".<ref>{{Harvnb|Chouliaras|Stavrakakis|1999|p=223}}.</ref>}} among seismologists it was greeted by a "wave of generalized skepticism".<ref>{{Harvnb|Mulargia|Gasperini|1992|p=32}}.</ref> In 1996, a paper VAN submitted to the journal [[Geophysical Research Letters]] was given an unprecedented public peer-review by a broad group of reviewers, with the paper and reviews published in a special issue;<ref>{{Harvnb|Geller|1996b}}; {{cite journal|title=Table of contents|journal=Geophysical Research Letters|volume=23|issue=11|date=27 May 1996|doi=10.1002/grl.v23.11}}</ref> the majority of reviewers found the methods of VAN to be flawed. Additional criticism was raised the same year in a public debate between some of the principals.<ref>The proceedings were published as ''A Critical Review of VAN'' {{Harv|Lighthill|1996}}. See {{Harvtxt|Jackson|Kagan|1998}} for a summary critique.</ref>{{efn|1=A short overview of the debate can be found in an exchange of letters in the June 1998 issue of ''Physics Today''.<ref>{{Harvnb|Geller|Jackson|Kagan|Mulargia|1998}}; {{Harvnb|Anagnostopoulos|1998}}.</ref>}}

A primary criticism was that the method is geophysically implausible and scientifically unsound.<ref>{{Harvnb|Mulargia|Gasperini|1996a|p=1324}}; {{Harvnb|Jackson|1996b|p=1365}}; {{Harvnb|Jackson|Kagan|1998}}; {{Harvnb|Stiros|1997|p=478}}.</ref> Additional objections included the demonstrable falsity of the claimed one-to-one relationship of earthquakes and SES,<ref>{{Harvnb|Drakopoulos|Stavrakakis|Latoussakis|1993|pp=223, 236}}; {{Harvnb|Stavrakakis|Drakopoulos|1996}}; {{Harvnb|Wyss|1996|p=1301}}.</ref> the unlikelihood of a precursory process generating signals stronger than any observed from the actual earthquakes,<ref>{{Harvnb|Jackson|1996b|p=1365}}; {{Harvnb|Gruszow|Rossignol|Tzanis|Le Mouël|1996|p=2027}}.</ref> and the very strong likelihood that the signals were man-made.<ref>{{Harvnb|Gruszow|Rossignol|Tzanis|Le Mouël|1996|p=2025}}.</ref>{{efn|1=For example the VAN "IOA" station was next to an antenna park, and the station at Pirgos, where most of the 1980s predictions were derived, was found to lie over the buried grounding grid of a military radio transmitter. VAN has not distinguished their "seismic electric signals" from artificial electromagnetic noise or from radio-telecommunication and industrial sources.<ref>{{Harvnb|Chouliaras|Stavrakakis|1999}}; {{Harvnb|Pham|Boyer|Chouliaras|Le Mouël|1998|pp=2025, 2028}}; {{Harvnb|Pham|Boyer|Le Mouël|Chouliaras|1999}}.</ref>}} Further work in Greece has tracked SES-like "anomalous transient electric signals" back to specific human sources, and found that such signals are not excluded by the criteria used by VAN to identify SES.<ref>{{Harvnb|Pham|Boyer|Chouliaras|Savvaidis|2002}}.</ref> More recent work, by employing modern methods of statistical physics, i.e., detrended fluctuation analysis (DFA), multifractal DFA and wavelet transform revealed that SES are clearly distinguished from signals produced by man made sources.<ref>{{Harvnb|Varotsos|Sarlis|Skordas|2003a}}</ref><ref>{{Harvnb|Varotsos|Sarlis|Skordas|2003b}}</ref>

The validity of the VAN method, and therefore the predictive significance of SES, was based primarily on the empirical claim of demonstrated predictive success.<ref>{{Harvnb|Stiros|1997|p=481}}.</ref> Numerous weaknesses have been uncovered in the VAN methodology,{{efn|1=For example it has been shown that the VAN predictions are more likely to follow an earthquake than to precede one. It seems that where there have been recent shocks the VAN personnel are more likely to interpret the usual electrical variations as SES. The tendency for earthquakes to cluster then accounts for an increased chance of an earthquake in the rather broad prediction window. Other aspects of this will be discussed below.}} and in 2011 the International Commission on Earthquake Forecasting for Civil Protection concluded that the prediction capability claimed by VAN could not be validated.<ref name=":5">{{Harvnb|ICEF|2011|pp=335–336}}.</ref> Most seismologists consider VAN to have been "resoundingly debunked".<ref>{{Harvnb|Hough|2010b|p=195}}.</ref> On the other hand, the Section "Earthquake Precursors and Prediction" of "Encyclopedia of Solid Earth Geophysics: part of "Encyclopedia of Earth Sciences Series" (Springer 2011) ends as follows (just before its summary): "it has recently been shown that by analyzing time-series in a newly introduced time domain "natural time", the approach to the critical state can be clearly identified [Sarlis et al. 2008]. This way, they appear to have succeeded in shortening the lead-time of VAN prediction to only a few days [Uyeda and Kamogawa 2008]. This means, seismic data may play an amazing role in short term precursor when combined with SES data".<ref name=":6">{{Harvnb|Uyeda|Nagao|Kamogawa|2011}}</ref>

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 (signal processing)|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 phenomena|critical phenomenon]].<ref>Varotsos, Sarlis & Skordas 2002;{{full citation needed|date=May 2020}} Varotsos 2006.{{full citation needed|date=May 2020}}; {{Harvnb|Rundle|Holliday|Graves|Turcotte|2012}}.</ref><ref>{{Harvnb|Huang|2015}}.</ref> A review of the updated VAN method in 2020 says that it suffers from an abundance of false positives and is therefore not usable as a prediction protocol.<ref name="auto">{{Harvnb|Helman|2020}}</ref> VAN group answered by pinpointing misunderstandings in the specific reasoning.<ref>{{Harvnb|Sarlis|Skordas|Christopoulos|Varotsos|2020}}</ref>