
158 E. I. Mashinskii / Natural Science 2 (2010) 155-159
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stress. Such stress stop supposes similar stop on the
stress-strain curve that can occur owing to the mi-
croplasticity process. Total strain = e + µ + v-e in
the small-strain range consists mainly of elastic and
microplastic component (e + µ), as viscoelastic com-
ponent v-e is comparatively small [10,11]. During
loading (or unloading), both components have own
contribution to the total strain. The stop in the course of
stress occurs when the stress reaches some critical
value σcr (for example, in the point b see inset (b) in
Figure 1). At that moment, the redistribution of con-
tribution between components occurs thus that contri-
bution of the microplastic component become pre-
dominant. In the extreme case, the strain increment
occurs only thanks to microplasticity as the increment
due to the elastic deformation does not occur at all [10].
Therefore, the yield process is also possible. The re-
grouping in components occurs thus that effective
modulus Eab and accordingly the stress and strain re-
main invariable during interval b – c. It is possible ow-
ing to the distinctive feature of rock microplasticity that
can both increase and decrease or even vanish during
stress. In the point c after delay, the stress recom-
mences own course with the same modulus. There is
the hierarchical set of the diverse critical stresses that
switch on the microplasticity sources when amplitude
increases (decreases). Thus, seismic wave switches on
the process of the anomalous redistribution of stresses
and strains and respectively adequate to it process of
the structural realignment in the rock. It takes a definite
time that leads to deformation delay. In order to ex-
clude the instrumental factor in appraisal of SMM, the
amplitude error of analog-digital converter is checked.
Testing of this device shows that the own error in pla-
teau duration does not exceed 2 microseconds in the
broad range of the amplitude steepness.
Similar deformation stops caused by microplasticity
were detected in C60 single crystals [20]. It is shown that
magnetic field manipulations lead to a change in the
strain rate, the decrease in the rate being accompanied by
a brief interruption of deformation. The deformation
delay (incubation period) was observed also in the
high-temperature superconductors, possessing by mi-
croplasticity [21]. Delay appearance is bound with pres-
ence of opposite internal stresses for decrease of which
time is required. The wave attenuation mechanism in the
rock with microplasticity (referring to the experiments
[10]) is theoretically substantiated also in work [22]. As
regards the mechanism of wave attenuation, the combi-
nation of known mechanisms is possible, for instance, as
the hybrid relaxation-hysteresis mechanism [12]. It must
not be ruled out also the acoustoplastic effect in the
rocks as in metals and alloys [23]. The instance of stress
jumps marked on seismic record evokes the great cau-
tion in interpretation of this effect, and therefore for the
time being, we do not examine this question.
4. CONCLUSIONS
The result of this work is the new knowledge about na-
ture of propagation of the mechanical oscillations in the
Earth. The unnoticed heretofore presence in seismic re-
cord of microplasticity manifestations was detected
thanks to the high-resolution signals measurements. The
quasi-static microplasticity of the rocks, dynamic mi-
croplasticity of many solid states denoted the prospect of
our search. The dynamic microplasticity in the rocks
definitely is bound with critical amplitudes but its de-
pendence on strain rate is not yet established. One may
surmise data about rock microplasticity will enlarge the
comprehension of some known effects that had not for-
merly of the satisfactory physical explanation. We see it
now in the delay effect of the arrival time and the pulse
shortening-widening.
As stated above, the nature of microplasticity in the
rocks can coincide with known mechanisms in the solid
states (for instance, dislocation microplasticity) or to be
quite other (quasi-microplasticity). In the last case in
spite of the difference in mechanism, the microplasticity
manifestations can be the same as in usual solid states.
This question requires subsequent clarification. Microplas-
ticity affects the little-known anelastic processes of the
small-amplitude wave propagation. The new knowledge
about nonlinear-anelastic processes during wave propa-
gation will help in discovery of new diagnostic indica-
tions permissive to increase the efficiency of seismic
method for search of oil-gas deposits.
5. ACKNOWLEDGMENT
The author thanks G.V. Egorov for the help in the experimental work.
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