From: bverreau@netcom.com (stargazer)
Subject: The VAN Method
Date: Thu, 20 Aug 92 07:36:01 GMT
Organization: Franciscan Assemblage
Reply-To: bverreau@netcom.com (stargazer)
Distribution: ca

I found a couple of new earthquake-related books at Kepler's [Menlo Park]
that might be of interest to readers of this group.  The first is a slim
volume [134 pp] entitled "Earthquake Prediction", Haroun Tazieff, McGraw-
Hill, QE538.8T3913 1992.  The work drew some attention in France where it
was first published in 1989 by M. Tazieff, former director of the French
National Scientific Research center.  The prediction scheme is called the
VAN method after the three Greek scientists who developed it, Profs.
Varotsos, Alexopoulos, and Nomikos.

The VAN theory - for those not previously acquainted - is descended from
observations reported by John Milne, father of the seismograph, in 1897
concerning changes in "telluric currents" preceding earthquakes.  Changes
in the electrical ground potential are claimed to correlate with subsequent
seismic disturbances.  The following text is the proponents' suggested
explanation for this phenomenon [bear in mind, this is a Greek-French-
English translation]:

 "The rocks of the Earth's crust consist of solids; these are crystals
  which contain microscopic impurities.  If we assume that the electrical
  charge of these impurities is different from the ions of the crystals
  that contain them, an interstitial gap which gives rise to a dipole is
  created, due to charge compensation (that is, electrical neutrality).
  The orientation of the dipole can change when an ion jumps this gap.
  The time required for this dipole to change is called the 'relaxation
  time,' and depends on the temperature and pressure.  When an electrical
  field is present, the dipoles tend to line up parallel to it.  However,
  when temperature and pressure conditions dictate excessively long relax-
  ation times, the dipoles essentially cannot rotate, and thus each one
  retains the alignment it had; in other words, they do not 'feel' the
  effect of the magnetic field.

 "But let us assume that while the temperature remains constant, the
  pressure experienced by the solid progressively increases.  This
  gradual change will lead to a gradual decrease in the relaxation time
  of the dipoles, and when the pressure reaches a certain critical value,
  the dipoles will be able to pivot freely and align themselves parallel
  to the electric field.  This change in polarization will be accompanied
  by emission of a piezoelectric current, that is, a current associated
  with a mechanical stress.  This is inevitably a transient phenomenon,
  since the current ceases as soon as all dipoles have aligned themselves
  with the electric field."

The setup for VAN monitoring is minimal compared to the equipment required
for ULF detection.

 "Each of these stations consists of at least two sensors, one oriented
  north-south and the other east-west.  The principle of these sensors
  is very simple:  two electrodes buried in the ground several dozen,
  hundred, or even a thousand feet apart, connected by a conductive wire
  to a voltage amplifier and a chart recorder."

Much effort is involved in calibrating each site for local geophysical
effects.  Characteristic earthquakes must be recorded to establish the
appropriate electrical 'signature' for a given location.  Triangulation
is used to estimate the point of origin for a disturbance.  Some sites
prove unsuitable because underlying features obstruct ground currents.

Whether or not you buy the theory - and I'm skeptical about the notion
of 'pressure [uniformly] reaching a certain critical value' - you have
to wonder about the claimed predictive success.  The physicists reported
to have correctly forecast 90% of all tremors in the M4-6 range during
an 8 month period in Greece (1988-89) using VAN.  All 17 correctly picked
tremors during that interval occurred within 10 days of the prediction,
within .5 order of magnitude, and had epicenters within 20 km. of the
announced locations.  All predictions (and misses) are supposedly
documented in telegrams sent to an official government agency charged
with earthquake preparedness.  If true, it would seem they were onto
something.

Tazieff spends much of the book railing against the 'experts'.  An
example paragraph:

 "The explanation for this attitude [hostility to the theory] lies, I
  believe, in a feeling of frustration associated with the fact that
  Varotsos, Alexopoulos, and Nomikos are not geophysicists, much less
  seismologists, but two solid-state physicists (V and A) and an
  electronics engineer (N), and they are thus outsiders in terms of
  Earth science.  That these 'outsiders' should have discovered how
  to predict earthquakes, a result that seismologists could not
  achieve despite decades of effort, is obviously a difficult thing
  to forgive.  What is more, if this method were to be officially
  adopted, the funding allocated each year to research in this area
  might be taken away from them.  Two good reasons to reject this
  heretical intrusion without even examining it."

In my mind this is where the book loses a lot of its credibility.
Paranoia and conspiracy theories are a hallmark of fringe science.
On the face of it, the evidence is intriguing, but...  One possible
source of error was pointed out to me by someone very knowledgeable
about such matters; the study may be flawed by sampling bias.  The
region chosen is so seismically active, that it is possible 'cook
the results' by selectively using quakes in the M4.5-5.0 range to
confirm hits, while ignoring those that would constitute misses.
Some studies are reported to have been published in the European
refereed journal called *Tectonophysics*.  I'll have to look it
up the next time I stop by the Stanford library.

The second book, "Earthquake Hazard Analysis", by Leon Reiter is
*much* more substantial.  I'll post that review when I've finished.
--
Bernie Verreau bverreau@netcom.COM
Netcom - Online Communication Services Redwood City, CA
Newsgroups: ca.earthquakes