VAN method
Encyclopedia
The VAN method is a controversial method for earthquake prediction
based on the assumption that minerals under mechanical stress emit characteristic electrical signals. The name of the method derives from the surname initials of each of its inventors, Greek physicist
s Panayotis Varotsos
, Caesar Alexopoulos and Kostas Nomikos. Currently (2010) the VAN team is part of the Solid Earth Physics Institute of the University of Athens, Greece and is headed by Professor Panayotis Varotsos.
component of 1 Hz or less and an amplitude proportional to the magnitude of the earthquake. According to the VAN team the SES are emitted by rocks under the stress caused by the movement of tectonic plates. They are attributed to the piezoelectric behaviour
of some mineral
s, especially quartz
, or to effects related to the behaviour of crystallographic defects under stress and they appear when the mechanical stress on rocks reaches a critical value, a few weeks before the earthquake.
The seismic electric signals propagate with relatively low attenuation along the tectonic faults, due to the increased electrical conductivity caused either by the intrusion of ground water in them or by the ionic characteristics of the minerals. These signals are detected at stations which consist of pairs of electrodes inserted into the ground, amplifiers and filters. They are then transmitted to the headquarters of the VAN team in Athens where they are recorded and evaluated. Currently the VAN team operates 9 stations, while in the past (1999) they could afford up to 17. The VAN team claims that they are able to predict earthquakes of magnitude larger than 5, with an uncertainty
of 0.7 units of magnitude and in a 2-hour to 11-day time window. The VAN stations have a degree of spatial selectivity. For example the station IOA, located near Ioannina
, detects seismic electric signals which correspond to tectonic activity in Western Peloponnese and the Ionian Sea, while it does not detect signals related to tectonic activity around Ioannina.
The generation of electric signals by minerals under high stress leading to fracture has been confirmed with laboratory experiments.
In recent years the VAN team has tried to improve the accuracy of the estimation of the time of the forthcoming earthquake by introducing the concept of natural time, a parameter which indicates the evolution of the process from the generation of the seismic electric signal to the fracture at the tectonic fault.
The VAN method is also used for investigation of seismic electric signals in Japan.
VAN has claimed to have observed at a recording station in Athens a perfect record of a one-to-one correlation between SESs and earthquake of magnitude ≥ 2.9 which occurred 7 hours later in all of Greece. However, it was later shown that the list of earthquake used for the correlation was false. Although VAN stated in their article that the list of earthquakes was that of the Bulletin of the National Observatory of Athenshttp://www.noa.gr/indexen.html (NOA) it was found that 37% of the earthquakes actually listed in the bulletin, including the largest one, were not in the list used by VAN for issuing their claim. In addition, 40% of the earthquake which VAN claimed had occurred were not in the NOA bulletin.
Examining the probability of chance correlation of 22 claims of successful predictions by VAN it was found that 74% were false, 9% correlated by chance, and for 14% the correlation was uncertain. No event correlated at a probability greater than 85%, whereas the level required in statistics for accepting a hypothesis test as positive is 99%, sometimes relaxed to 95%.
None of the earthquakes which Van claimed were preceded by SESs generated an SES themselves and an analysis of the propagation properties of SESs in the Earth’s crust showed that it is impossible that signals with the amplitude reported by VAN could have been generated by small earthquakes and transmitted over the several hundred kilometers distances from the epicenter to the receiving station.
VAN’s publications are characterized by a lack of addressing the problem of eliminating the many and strong sources of change in the magneto-electric field measured by them, such as telluric currents and neighbors of Varotsos turning on and off their television set in suburban Athens, by a lack of statistical testing of the validity of their hypothesis, by changing the parameters of the hypothesis constantly (the moving goal post technique), and by a belief that phenomena of rock physics seen in the laboratory can be assumed to take place in the Earth’s seismogenic crust.
One inherent problem of the method is that, in order for any prediction to be useful, it has to predict a forthcoming earthquake with a reasonable accuracy with respect to timeframe, epicenter and magnitude. Otherwise, if the prediction is too vague, no feasible decision (such as to evacuate the population of a certain area for a given period of time) can be made. The VAN team have been arguing that, as the sensor rod network expands and its data processing technique is refined, its predictions will become increasingly useful.
Major opponents of VAN were the Greek seismologists Vassilis Papazachos
and G. Stavrakakis. The debate between Papazachos and the VAN team has repeatedly caused public attention in their home country Greece
and has been extensively discussed in the Greek media.
Earthquake prediction
An earthquake prediction is a prediction that an earthquake of a specific magnitude will occur in a particular place at a particular time . Despite considerable research efforts by seismologists, scientifically reproducible predictions cannot yet be made to a specific day or month...
based on the assumption that minerals under mechanical stress emit characteristic electrical signals. The name of the method derives from the surname initials of each of its inventors, Greek physicist
Physicist
A physicist is a scientist who studies or practices physics. Physicists study a wide range of physical phenomena in many branches of physics spanning all length scales: from sub-atomic particles of which all ordinary matter is made to the behavior of the material Universe as a whole...
s Panayotis Varotsos
Panayotis Varotsos
Panayotis Varotsos is a Greek physicist , full professor in the Department of Physics of the University of Athens since 1986, notable for his VAN method to predict earthquakes. His group claims the ability to identify electromagnetic signals that are precursors to earthquakes...
, Caesar Alexopoulos and Kostas Nomikos. Currently (2010) the VAN team is part of the Solid Earth Physics Institute of the University of Athens, Greece and is headed by Professor Panayotis Varotsos.
Description of VAN
Prediction of earthquakes with this method is based on the detection, recording and evaluation of Seismic Electric Signals or SES. These electric signals have a fundamental frequencyFrequency
Frequency is the number of occurrences of a repeating event per unit time. It is also referred to as temporal frequency.The period is the duration of one cycle in a repeating event, so the period is the reciprocal of the frequency...
component of 1 Hz or less and an amplitude proportional to the magnitude of the earthquake. According to the VAN team the SES are emitted by rocks under the stress caused by the movement of tectonic plates. They are attributed to the piezoelectric behaviour
Piezoelectricity
Piezoelectricity is the charge which accumulates in certain solid materials in response to applied mechanical stress. The word piezoelectricity means electricity resulting from pressure...
of some mineral
Mineral
A mineral is a naturally occurring solid chemical substance formed through biogeochemical processes, having characteristic chemical composition, highly ordered atomic structure, and specific physical properties. By comparison, a rock is an aggregate of minerals and/or mineraloids and does not...
s, especially quartz
Quartz
Quartz is the second-most-abundant mineral in the Earth's continental crust, after feldspar. It is made up of a continuous framework of SiO4 silicon–oxygen tetrahedra, with each oxygen being shared between two tetrahedra, giving an overall formula SiO2. There are many different varieties of quartz,...
, or to effects related to the behaviour of crystallographic defects under stress and they appear when the mechanical stress on rocks reaches a critical value, a few weeks before the earthquake.
The seismic electric signals propagate with relatively low attenuation along the tectonic faults, due to the increased electrical conductivity caused either by the intrusion of ground water in them or by the ionic characteristics of the minerals. These signals are detected at stations which consist of pairs of electrodes inserted into the ground, amplifiers and filters. They are then transmitted to the headquarters of the VAN team in Athens where they are recorded and evaluated. Currently the VAN team operates 9 stations, while in the past (1999) they could afford up to 17. The VAN team claims that they are able to predict earthquakes of magnitude larger than 5, with an uncertainty
Measurement uncertainty
In metrology, measurement uncertainty is a non-negative parameter characterizing the dispersion of the values attributed to a measured quantity. The uncertainty has a probabilistic basis and reflects incomplete knowledge of the quantity. All measurements are subject to uncertainty and a measured...
of 0.7 units of magnitude and in a 2-hour to 11-day time window. The VAN stations have a degree of spatial selectivity. For example the station IOA, located near Ioannina
Ioannina
Ioannina , often called Jannena within Greece, is the largest city of Epirus, north-western Greece, with a population of 70,203 . It lies at an elevation of approximately 500 meters above sea level, on the western shore of lake Pamvotis . It is located within the Ioannina municipality, and is the...
, detects seismic electric signals which correspond to tectonic activity in Western Peloponnese and the Ionian Sea, while it does not detect signals related to tectonic activity around Ioannina.
The generation of electric signals by minerals under high stress leading to fracture has been confirmed with laboratory experiments.
In recent years the VAN team has tried to improve the accuracy of the estimation of the time of the forthcoming earthquake by introducing the concept of natural time, a parameter which indicates the evolution of the process from the generation of the seismic electric signal to the fracture at the tectonic fault.
The VAN method is also used for investigation of seismic electric signals in Japan.
Criticism of VAN
The usefulness of the VAN method for prediction of earthquakes has been a matter of debate. Both positive and negative criticism on the VAN method is summarized in the 1996 book "A Critical Review of VAN", edited by Sir James Lighthill. A very critical review of the methodology was published by Y. Y. Kagan of UCLA in 1997.VAN has claimed to have observed at a recording station in Athens a perfect record of a one-to-one correlation between SESs and earthquake of magnitude ≥ 2.9 which occurred 7 hours later in all of Greece. However, it was later shown that the list of earthquake used for the correlation was false. Although VAN stated in their article that the list of earthquakes was that of the Bulletin of the National Observatory of Athenshttp://www.noa.gr/indexen.html (NOA) it was found that 37% of the earthquakes actually listed in the bulletin, including the largest one, were not in the list used by VAN for issuing their claim. In addition, 40% of the earthquake which VAN claimed had occurred were not in the NOA bulletin.
Examining the probability of chance correlation of 22 claims of successful predictions by VAN it was found that 74% were false, 9% correlated by chance, and for 14% the correlation was uncertain. No event correlated at a probability greater than 85%, whereas the level required in statistics for accepting a hypothesis test as positive is 99%, sometimes relaxed to 95%.
None of the earthquakes which Van claimed were preceded by SESs generated an SES themselves and an analysis of the propagation properties of SESs in the Earth’s crust showed that it is impossible that signals with the amplitude reported by VAN could have been generated by small earthquakes and transmitted over the several hundred kilometers distances from the epicenter to the receiving station.
VAN’s publications are characterized by a lack of addressing the problem of eliminating the many and strong sources of change in the magneto-electric field measured by them, such as telluric currents and neighbors of Varotsos turning on and off their television set in suburban Athens, by a lack of statistical testing of the validity of their hypothesis, by changing the parameters of the hypothesis constantly (the moving goal post technique), and by a belief that phenomena of rock physics seen in the laboratory can be assumed to take place in the Earth’s seismogenic crust.
One inherent problem of the method is that, in order for any prediction to be useful, it has to predict a forthcoming earthquake with a reasonable accuracy with respect to timeframe, epicenter and magnitude. Otherwise, if the prediction is too vague, no feasible decision (such as to evacuate the population of a certain area for a given period of time) can be made. The VAN team have been arguing that, as the sensor rod network expands and its data processing technique is refined, its predictions will become increasingly useful.
Major opponents of VAN were the Greek seismologists Vassilis Papazachos
Vassilis Papazachos
Vassilis Papazachos is a Greek seismologist.Born 30 September 1929 in the village of Smokovo in Karditsa Prefecture, Vassilis Papazachos studied physics in the Aristotle University of Thessaloniki. He first became involved in geophysics as an assistant of professor Angelos Galanopoulos...
and G. Stavrakakis. The debate between Papazachos and the VAN team has repeatedly caused public attention in their home country Greece
Greece
Greece , officially the Hellenic Republic , and historically Hellas or the Republic of Greece in English, is a country in southeastern Europe....
and has been extensively discussed in the Greek media.
External links
- IEEE Spectrum: Impending earthquakes have been sending us warning signals—and people are starting to listen
- Nature debates. Is the reliable prediction of individual earthquakes a realistic scientific goal?
- Panayiotis Varotsos, VAN earthquake prediction method, 08-06-2010. Ανακτήθηκε στις 08-06-2010.