ISSN 1028334X, Doklady Earth Sciences, 2010, Vol. 433, Part 1, pp. 901–905. © Pleiades Publishing, Ltd., 2010.
Original Russian Text © I.L. Gufeld, A.V. Afanasyev, V.V. Afanasyeva, O.N. Novoselov, 2010, published in Doklady Akademii Nauk, 2010, Vol. 433, No. 1, pp. 92–96.
901
Despite significant efforts in research into medium
and shortrange seismic hazards, the final result that
could allow us to predict a future epicentral zone
remains unclear. These forecasts use empirical experi
ence based on laboratory models of material destruc
tion and distinguishing local perturbations of different
parameters of the medium. In this work, we analyze
the seismotectonic situation based on monitoring data
of integral lithospheric parameters reflecting continu
ous variability of the parameters on a regional scale.
Longterm experience of monitoring [1] and anal
ysis of geotectonic situations allow us to formulate
new goals, which require that two factors be taken into
account.
The first one is that continuous variations of local
and integral lithospheric parameters on various scales
(deformation, water level, conductivity, microseismic
noise, velocities of seismic waves, weak seismicity
regime, and others) are described by a set of harmonics
with periods from hours and days to many months and
years [2]. Such rapid and continuous variations of the
medium parameters reflecting the corresponding vari
ations in the volume stressed state (VSS) cannot be
associated with the response of the medium to very
slow tectonic motions. The nature of fast variations in
VSS is considered with the account for the interaction
of ascending light gases (hydrogen, helium) with the
solid phase [3, 4]. When the gradients of lithostatic
pressure and temperature are quasiconstant, the
influence of mobile ascending flows of light gases
becomes the main variable factor controlling the cur
rent VSS variation in the medium. This approach
allows us to show that seismicity, including strong
seismicity, is caused by weak variations (fluctuations)
of VSS near the limiting level of energy saturation in
the medium [4].
The second one is that it is obvious that regional
excitation of a block medium before strong and cata
strophic earthquakes [5, 6] is a proved fact. The
regional character of medium excitation is manifested
in the peculiarities of the spatial distribution of weak
and moderate seismicity (algorithm RTL [7]), as well
as in local anomalies of different fields at distances
r
~
exp
M
(km) from the future epicenters. However, epi
central zones of strong earthquakes do not coincide
with the regions of maximum perturbations, and
earthquakes can occur after their termination [5, 7, 8].
Therefore, the observed local perturbations of one
parameter or another, including fast perturbations, do
not play the role of earthquake forerunners, but reflect
only the nonuniform process of regional excitation in
a block medium.
The nonuniformity of a regional medium excita
tion is related to the peculiarities of the geological
structure and its fast response to the interaction pro
cesses with the ascending flow of light gases [9]. Vari
ations in the structural elastic sensitive modules of the
medium would be a consequence of the interaction
between variable ascending flows of light gases with
the solid phase, during which changes in the structure
and volume of its elements occur [3]. This will lead to
the oscillation regime of VSS in a maximum energy
saturated medium on different spatiotemporal scales,
which can be manifested in the variations of velocities
of longitudinal
V
P
and shear
V
S
waves
~
1.15 ,
where
E
and
μ
are Young’s modulus and
the shear modulus, respectively; the Poisson coeffi
cient is assumed as 0.25–0.35 .
This paper is dedicated to study of the oscillation
VSS regime in a geological medium reflecting either a
stable or an unstable state of the medium and its vari
V
P
V
S
⎝
⎛
E
μ
⎝⎠
⎛⎞
1/2
⎠
⎞
Trigger Effects of Seismotectonic Processes
in a Dynamically Changing Geological Medium
I. L. Gufeld
a
, A. V. Afanasyev
b
, V. V. Afanasyeva
b
, and O. N. Novoselov
b
Presented by Academician V.N. Strakhov November 15, 2009
Received November 10, 2009
DOI:
10.1134/S1028334X10070123
a
Schmidt Joint Institute of Physics of the Earth,
Russian Academy of Sciences, ul. Bol’shaya Gruzinskaya 10,
Moscow, 123810 Russia
email: igufeld@korolevnet.ru
b
Moscow State Forest University, Pervaya Institutskaya ul. 1,
Mytishchi, Moscow oblast, 141005 Russia
GEOPHYSICS