Earthquake professionals have for many decades recognized the benefits
to society from reliable earthquake predictions, but uncertainties
regarding source initiation, rupture phenomena, and accuracy of both the
timing and magnitude of the earthquake occurrence have oftentimes
seemed either very difficult or impossible to overcome. The problem is
that most of these methods cannot be adequately tested and evaluated
either because of (a) lack of a precise definition of “prediction”
and/or (b) shortage of data for meaningful statistical verification.
This is not the case for the pattern recognition algorithm M8 designed
in 1984 for prediction of great, Magnitude 8, earthquakes, hence its
name. By 1986, the algorithm was rescaled for applications aimed at
smaller magnitude earthquakes, down to M5+ range, and since then it has
become a useful tool for systematic monitoring of seismic activity in a
number of test seismic regions worldwide. After confirmed predictions of
both the 1988 Spitak (Armenia) and the 1989 Loma Prieta (California)
earthquakes, a “rigid test” to evaluate the efficiency of the
intermediate-term middle-range earthquake prediction technique has been
designed. Since 1991, each half-year, the algorithm M8 alone and in
combination with its refinement MSc has been applied in a real-time
prediction mode to seismicity of the entire Earth, and this test
outlines, where possible, the areas in the two approximations where
magnitude 8.0+ and 7.5+ earthquakes are most likely to occur before the
next update. The results of this truly global 20-year-old experiment are
indirect confirmations of the existing common features of both the
predictability and the diverse behavior of the Earth’s naturally fractal
lithosphere. The statistics achieved to date prove (with confidence
above 99 %) rather high efficiency of the M8 and M8-MSc predictions
limited to intermediate-term middle- and narrow-range accuracy. These
statistics support the following general conclusions—(1) precursory
seismic patterns do exist; (2) the size of an area where precursory
seismic patterns show up is much larger than that of the source zone of
the incipient target earthquake; (3) many precursory seismic patterns
appear to be similar, even in regions of fundamentally different
tectonic environments; and (4) some precursory seismic patterns are
analogous to those in advance of extreme catastrophic events in other
complex nonlinear systems (e.g., magnetic storms, solar flares,
“starquakes”, etc.)—that are of high importance for further searches of
the improved earthquake forecast/prediction algorithms and methods.
Affiliations:
Vladimir G. Kossobokov
Russian Academy of Sciences, Institute of Earthquake Prediction Theory and Mathematical Geophysics, 84/32 Profsoyuznaya Street, 117997, Moscow, Russian Federation
Institut de Physique du Globe de Paris, 1, rue Jussieu, 75238, Paris, France
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