Free oscillations of earthquake source

Aptikaev, F.

Автор: Aptikaev Felix
Сборник: Abstract Book. COP-29 Side Event. The Sixth Eurasian Conference RISK-2024 “Innovations in Minimization of Natural and Technological Risks of Climate Changes: Methodology and Practice” (Baku, Azerbaijan, November, 27 – 29, 2024)
Тезисы
Год издания: 2024
Место издания: “ZERDARI NESR” MMC Baku, Azerbaijan
Первая страница: 85
Последняя страница: 85
Аннотация: The definition of a source as an area in which part of the deformation energy of rocks is converted into the energy of seismic waves is used. The author examined the level of the soil surface on the profile of geophones at different times during explosions. It was shown that stresses arising in the environment cause, in addition to the known longitudinal and transverse waves, natural vibrations of a certain volume of rocks surrounding the epicenter. The amplitude of these oscillations is significantly higher than the amplitude of the generated seismic body waves. Similar phenomena should occur during earthquakes. The only difference is that during earthquakes, stress in the rocks exists even before movement along the fault begins. The characteristics of seismic vibrations that confirm this hypothesis are considered. According to empirical data, near the fault the amplitudes on loose soils are no higher than on rocky ground, other parameters of oscillations - the predominant period of the response spectrum and the duration of oscillations – also do not depend on ground conditions. However, seismic intensity on loose soils increases due to a decrease in the bearing capacity of the soil. Previously, only soil liquefaction was usually considered such a factor. But, there is a method for vibrating piles to significant depths (up to 70 m) without the liquefaction process. At acceleration amplitudes on the vertical component PGA > 0.1 g, the shear strength of non-rocky soils in the horizontal plane can decrease several times. It turned out that the influence of movement along the fault is limited in space. Oscillation energy is released up to the distance log Rb = - 0.77 + M/3, where Rb is the shortest distance to the fault surface, M – magnitude based on surface waves. Accordingly, the seismic source has the shape of a parallelepiped with smoothed edges. Errors of programs NERA, STRATA and others are associated with the assumption of passing waves. Existing ideas about the influence of soil conditions on the parameters of seismic ground motion are valid only in the far-field zone. Moreover, only half of the increase in seismic intensity is associated with a change in amplitude, and the second half is associated with a change in the duration of oscillations. The last factor, according to empirical data, has the same effect on the damageability of construction objects as the acceleration amplitude. Unfortunately, this factor is not yet taken into account in building codes. Since instrumental estimates of seismic intensity based on accelerations, velocities and displacements generally do not coincide, one can think that the spectral composition of vibrations also affects seismic intensity.
Добавил в систему: Аптикаев Феликс Фуадович

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