Interacting inclined strike-slip faults in a layered medium

Two inclined, interacting, strike-slip faults, both buried, situated in a viscoelastic layer, resting on and in welded contact with a viscoelastic half space, representing the lithosphere-asthenosphere system, is considered. Solutions are obtained for the displacements, stresses and strains, using a technique involving the use of Green’s functions and integral transforms, for three possible cases - the case when no fault is slipping, the case when one fault is slipping and the other is locked and the case when both the faults are slipping. The effect of sudden movement across one fault on the shear stress near the fault itself and near the other faults has been investigated. Some situations are identified where a sudden movement across one fault results in the release of shear stress near the other fault, reducing the possibility of seismic movements across it. Other situations are also identified where a sudden movement across one fault increases the possibility of seismic fault movements. A detail study may lead to an estimation of the time span between two consecutive seismic events near the mid points of the faults. It is expected that such studies may be useful in understanding the mechanism of earthquake processes and may be identified as an earthquake precursor.

Using the automated Verasonics system for physical modeling of skeletal muscle biomechanics

The paper describes the use of the Verasonics research system for physical modeling of skeletal muscle biomechanics. The scheme of the acoustic system is described. The path of receiving and processing the signal is presented. A brief overview of the operation of software algorithms for the implementation of methods of ultrasound diagnostics is made. A mathematical model of skeletal muscle as a flat-layered medium is considered. The implementation of this model in the form of a fibers agar phantom is proposed. Using the Verasonics acoustic system shear velocities of physical fibers agar phantom were measured. Shear modules for agar and fibers were calculated. The obtained values are consistent with similar characteristics of native muscles and connective tissue fibers.

Research on the influence of bubble curtains on shock wave fields of the underwater explosion

Shock waves, which derive from explosions, generate reflected and refracted waves when propagating in the layered medium with various acoustic stiffness. Depending on the acoustic characteristic of each layer of the medium, properties of reflected and refracted waves will increase or decrease pressures/stresses at the investigated point of medium, compared to influences of explosive shock waves (incident waves) propagated in a homogeneous and isotropic medium. Based on this mechanical physical property, scientists have studied a diversity of solutions decreasing effects of explosive shock waves in various medium such as rock and soil, water, air. However, currently there have not been any comprehensive theoretical studies on the reduction in intensity of the underwater explosion shock wave when interacting with bubble curtain. By using the analytical method and the virtual explosive method, the paper presents the propagation rule of new waves formed when the underwater explosion shock wave interacts with the bubble curtain. The results showed that the more the thickness of the bubble curtain or the higher the bubble content or the longer the distance from the explosive to the curtain, the weaker the intensity of the shock wave when passing through the curtain.

Study on Vibration Response of Layered Media under the Impact Load

To study the vibration response of the layered medium under impact loading, single-layer concrete slabs, multilayer concrete slabs, and multilayer concrete slabs with a cemented filling layer were used as the working media to simulate the layered medium. A large number of impact loading tests were carried out by using a simple drop hammer device designed by us. The experimental results indicate that, under the impact load, the vibration response of the surface of the medium decreases with the increase in the distance to the impact source, showing the law of fast attenuation near field and slow attenuation far field, and the vibration energy moves to the low-frequency component; the vibration response increases with the increase in the impact energy, and the difference in the vibration response caused by the impact energy decreases as the distance increases; the vibration response is negatively correlated with the thickness of the dielectric layer, and the divergence of vibration response caused by impact energy decreases with the increase in the thickness of the dielectric layer. Due to the existence of the free surface and bedding, the vibration response of the layered medium surface increases with the increase in the number of layers and the vibration velocity response increases with the increase in the distance to the impact source when it is close to the free surface and far from the vibration source. For the filling of the cemented layer, the vibration response of the layered concrete slab becomes more complex under impact loading, showing obvious disorder. At the same time, this paper also used the dimensional analysis method to establish the calculation model of the peak response of vibration velocity of layered media under the impact load, which provided an idea for determining the peak response of vibration velocity of the layered media.

Gaivoron—Zavallia section of the Middle Pobuzhzhіa is the most representative part of the granulite complex of the Ukrainian Shield (structural-tectonophysical results and magnetometric studies)

In the article according to the geological and geophysical data of the well-exposed areas of development of Archean rocks of the Ukrainian Shield, two alternative approaches to establishing the structure and stratigraphy of the oldest granulite complexes are discuss. The outcrops of the enderbite-gneiss complex up to 3.6—3.8 billion years old are located along the Southern Bug River between the Gaivoron town and the Zavallia village. The first, «stratigenic-metamorphogenic» approach assumes that the main features of the composition and structure of the Lower Archean complexes are inherited from the original stratotypic strata. These strata are transformed in the conditions of quasi-isochemical metamorphism with preservation of the sequence of formation in section and the primary constitution in the form of stratification, rhythmicity, direction of change of their composition vertically and laterally. On the structural-formation map and geological section of the Gaivoron—Zavallia section, the Archean granulite complex is shown in the form of a synclinorium composed of four adjacent formations, which are equated to the world of metamorphosed volcanic-sedimentary rocks. The second, «deformation-metamorphogenic» approach, which is supported by the authors of this article, is based on the idea that the granulite complex of Pobuzhzhіa is a subvertically layered medium formed by tangential tectonic forces. The latter lead to shear deformations and displacement of matter at the atomic-molecular (with mineral transformation of rocks) and rock masses at the regional level. This creates structural and textural elements that are superimposed on the primary structure of rocks and often erase it. Field structural-tectonophysical, tectonofacial and magnetometric studies, its results are presented in the article. It was performed specifically to compare these two concepts. Magnetometric studies have shown that the enderbite-gneiss complex of the district by its magnetic characteristics belongs to the middle and lower crust of the Ukrainian Shield.

Passive seismic data processing methods to identify contrast intrasalt interlayers in the geological section of the Astrakhan Arch

The article examines the problem of processing microseismic noise (MN) to identify and evaluate occurrence depth of contrasting geological objects – intersalt interlayers with a potentially high formation pressure. If it is impossible to use artificial wave sources, statistic processing of passive seismic data becomes critical. Due to the accumulation of power spectral density (PSD) during a long-term recording of MN the deterministic medium effect on a random signal spectrum is identified. PSD modulation when the surface or the bottom of the layered medium is exposed to white noise is expressed in terms of the Green’s function (GF) of a wave equation. Relevant GF variations corresponding to the layers form the basis for accumulated PSD approximation, and indicate the depth and contrast of the target features.