Reestablishing intermediateterm realtime prediction of strong earthquakes in the Vrancea region

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Re-establishing intermediate-term real-time
prediction of strong earthquakes in the Vrancea
region

• V. Kossobokov1,2, L. Romashkova1
• International Institute of Earthquake Prediction
  Theory and Mathematical Geophysics,
• Russian Academy of Sciences,
• 79-2 Warshavskoye Shosse, Moscow 113556, Russian
  Federation
•     Institute de Physique du Globe de Paris,
• 4 Place Jussieu, 75252 Paris, Cedex 05, France
• E-mail volodya_at_mitp.ru or volodya_at_ipgp.jussieu.fr
  

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Vrancea region
Vrancea (Romania) is a geographical region
between Eastern and Southern Carpathian
Mountains. The region is characterized by a
rather high level of seismic activity mainly at
intermediate (up to 200 km) depths. These
intermediate-depth earthquakes occur between
450-460N and 260-270E. The shallow earthquakes
are dispersed over much broader territory.
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USGS/NEIC Global Hypocenter Data Base
The annual number of earthquakes, 1930-2005, in
the region
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ROMPLUS catalog of earthquakes (prepared by Dr.
Nicoleta Cadicheanu, Institute of Geodynamics of
the Romanian Academy)8151 hypocenters,
1900-2005
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ROMPLUS catalog of earthquakesM6.0 or larger
events, 1900-2005
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ROMPLUS catalog of earthquakesMagnitude vs. Time
Magnitude 2 or larger earthquakes are
systematically reported since the beginning of
the catalog in 1977.
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ROMPLUS catalog of earthquakesAnnual Number of
Earthquakes of Different Magnitude
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ROMPLUS catalog of earthquakesGutenberg-Richter
plot (1977-2005)
The list of magnitude 2.5 or larger events is
reasonably complete
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ROMPLUS catalog of earthquakesDepth vs. Time
(M2.5, 1977-2005)
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ROMPLUS catalog of earthquakesDepth (ordinate)
vs. Number of M2.5 in 1977-2005 (abscissa)
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ROMPLUS catalog of earthquakesThe Benioff
Strain Release at Depth and Near Surface vs. Time
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ROMPLUS catalog of earthquakesThe Benioff
Strain Release at Depth and Near Surface vs. Time
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ROMPLUS catalog of earthquakesInter-event Time
vs. Time (M2.5, 1977-2005)
Black line marks 10 events trailing average
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The commonly accepted definitions of the main-
and aftershocks have too long time intervals that
look inadequate in the Vrancea region e.g., the
Gardner-Knopoff methoddefines just about 1/3 of
M2.5 events as mainshocks.
Catalog of mainshocks
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We have analyzed in detail the local inter-event
times after strong, moderate, and light
earthquakes and suggested shorter time span for
aftershock sequences i.e., 2 days for M2.5-5.0,
4 days for M5.0-5.5, 8 days for M5.5-6.0,16 days
for M6.0-6.5, 32 days for M6.5-7.0, 64 days for
M7.0-9.0.These limits resulted about 70 of
M2.5 events as mainshocks (doubling of the
limits for Mgt4.5 does not change much - comes
with 68)
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M8 algorithm
(available from IASPEI Software Library, Vol. 6.
Seismol. Soc. Am., El Cerrito, CA, 1997)

• This intermediate-term earthquake prediction
  method was designed by retroactive analysis of
  dynamics of seismic activity preceding the
  greatest, magnitude 8.0 or more, earthquakes
  worldwide, hence its name.
• Its prototype (Keilis-Borok and Kossobokov, 1984)
  and the original version (Keilis-Borok and
  Kossobokov, 1987) were tested retroactively. The
  original version of M8 is subject to the on-going
  real-time experimental testing. After a decade
  the results confirm predictability of the great
  earthquakes beyond any reasonable doubt.
• The algorithm is based on a simple physical
  scheme

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General scheme
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Criterion in the phase space

• The algorithm M8 uses traditional description of
  a dynamical system adding to a common phase space
  of rate (N) and rate differential (L)
  dimensionless concentration (Z) and a
  characteristic measure of clustering (B).
• The algorithm recognizes criterion, defined by
  extreme values of the phase space coordinates, as
  a vicinity of the system singularity. When a
  trajectory enters the criterion, probability of
  extreme event increases to the level sufficient
  for its effective provision.

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M8 algorithm retroactive performance

• Retrospectively (Keilis-Borok and Kossobokov,
  1990) the standard version of the algorithm was
  applied to predict the largest earthquakes (with
  M0 ranging from 8.0 to 4.9) in 14 regions.
• 25 out of 28 predicted in 16 of the space-time
  considered.
• Modified versions in 4 regions of lower seismic
  activity predicted
• all the 11 largest earthquakes in 26 of the
  space-time considered.

The Vrancea region was among the four.
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Modified version of the M8 algorithm in the
Vrancea region (Kossobokov, 1986)

• Catalog of earthquakes (????????????? ? ????) was
  restricted to depths below 60 km and magnitudes
  above 3.3 (K10 or larger) due to the
  completeness requirements
• These provided the annual rate of 3 events
  instead of 20 (as in the standard version).

Apparently, the ROMPLUS catalog provides enough
data for application of the standard version of
the M8 algorithm.
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The standard version of M8 algorithm applied to
ROMPLUS catalog M7.0
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The standard version of M8 algorithm applied to
ROMPLUS catalog

• Of course, the results are not a full
  verification although these are -
• stable to variations of the data,
• different definitions of mainshocks,
• magnitude of the target earthquakes, and
• other parameters of the M8 algorithm
• - however, apparently the region is entering the
  Time of Increased Probability for a strong (or
  even major) earthquake.

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Conclusion

• The positive results of the Global Test of M8 and
  those obtained in applications of the modified
  (Kossobokov, 1986) and the standard (present
  study) versions of M8 algorithm are encouraging
  enough to suggest setting anew the real-time
  intermediate-term middle-range prediction
  experiment in the Vrancea region aimed at M7.0,
  M6.5, and M6.0 earthquakes.

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Next steps

• Setting up the real-time prediction experiment in
  the Vrancea region requires
• the routine real-time compilation of the ROMPLUS
  catalog updates
• the black box version of the data processing
• scheduling of the predictions updates.
• All the three to be established and fixed in full
  detail with the Institute of Geodynamics of the
  Romanian Academy by the end of 2006.