2,305 research outputs found
On two approaches to studying the aftershocks of a strong earthquake
The paper is devoted to comparing two approaches to the study of aftershocks.
The methodological foundations of the traditional approach were laid many years
ago. A new approach has emerged relatively recently. The two approaches differ
from each other in the object, purpose and method of research. The differences
are as follows. With the new approach, attention is focused not on aftershocks,
but on the source of the earthquake. The evolution of the source is studied
experimentally, and not the degradation of the frequency of aftershocks.
Instead of a speculative selection of empirical formulas, the source
deactivation coefficient is measured, variations in the coefficient are
observed, and only on the basis of measurements and observations are
conclusions drawn about the dynamics of the source. Thus, the divergence
between the two approaches is doctrinal. The new approach turned out to be
effective. Through targeted analysis of aftershock data, the Omori epoch and
the phenomenon of bifurcation of the earthquake source were discovered. The
purpose of further research is indicated. Keywords: earthquake source, Omori
law, Hirano-Utsu law, logistic law, deactivation coefficient, bifurcation,
master equation, methodology.Comment: 11 pages, 3 figure
Energy flows in the earthquake source before and after the main shock
We proceeded from general physical concepts based, on the one hand, on the
Umoff-Poynting theorem, and on the other, on the phenomenological theory of
earthquakes, and formulated the following question: What are the directions of
energy flows in the earthquake source before and after the formation of a main
rupture in it? A non-standard technique for experimental research of this issue
has been developed. The epicentral zone of the main shock is considered as a
kind of track detector, and foreshocks and aftershocks are considered as marks
(tracers) marking the propagation in the source of some factor that has energy
and stimulates the excitation of foreshocks and aftershocks in a
stressed-strained rock mass. By processing and analyzing a large volume of
observation data, it was found that over time, foreshocks, on average, approach
the epicenter of the main shock, while aftershocks, on the contrary, move away
from the epicenter. A method is indicated for verifying the result by studying
the magnitude dependence of foreshock convergence and aftershock divergence.
Keywords: foreshock, aftershock, main rupture, evolution equation, nonlinear
diffusion waves, fault length
On the proper time of the earthquake source
The concept of proper time, which is different from universal time, has been
introduced into the physics of earthquakes. The global activity of strong
earthquakes was chosen as the object of study. We consider the sequence of
earthquakes as a random process of the Poisson type. Comparatively weak
earthquakes are used as the underground clock, the ticking of which marks the
course of proper time. The Poisson distribution is compared with the
distributions for two sequences of strong earthquakes. One of the sequences is
ordered by calendar time, and the second by proper time. The result of the test
showed that the distribution of events ordered by proper time is closer to the
Poisson distribution than the distribution of events ordered by calendar time.
We explain this by non-stationarity, which is an immanent property of the
Earth's lithosphere.Comment: 9 pages, 5 figure
Electromagnetic signals produced by elastic waves in the Earth’s crust
The paper describes the excitation of
geoelectromagnetic-field oscillations caused by elastic waves propagating in the Earth’s crust and generated by
natural and anthropogenic phenomena, such as earthquakes, explosions, etc. Two mechanisms of electromagnetic signal generation, i.e. induction and electrokinetics ones, are considered and a comparative analysis between them is carried out. The first mechanism is associated with the induction of Foucault currents due to movements of the Earth’s crust in the core geomagnetic field. The second mechanism is connected with movements of liquids filling pores and cracks of rocks. An equation is derived for describing in a uniform way these two manifestations of seismomagnetism. The equation is solved for body and surface waves. The study shows that a magnetic precursor signal is moving in the front of elastic waves
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