scholarly journals FEATURES OF THE DEEP VELOCITY STRUCTURE OF THE TRANS-BAIKAL SECTION OF THE CENTRAL ASIAN FOLDED BELT FROM SEISMOLOGY AND GPS DATA (IN THE ALIGNMENT OF THE REFERENCE PROFILE 1-SB)

2020 ◽  
Vol 39 (5) ◽  
pp. 56-68
Author(s):  
V.M. Solovyev ◽  
◽  
A.S. Salnikov ◽  
V.S. Seleznev ◽  
V.V. Chechelnitsky ◽  
...  
Keyword(s):  
Baikal Region ◽  
Velocity Structure ◽  
Baikal Rift Zone ◽  
Earth’S Crust ◽  
S Wave ◽  
Southeastern Part ◽  
S Waves ◽  
Central Asian ◽  
Boundary Velocity ◽  
Earth's Crust

The materials of deep seismic studies on the reference geophysical profile 1-SB and areal interpretation of seismological data in the Trans-Baikal part of the Central Asian folded belt are presented. It is shown that longitudinal and transverse waves from the reference boundaries in the Earth's crust and Moho surface were registered using explosions and powerful vibration sources on the 1200-km geophysical profile 1-SB in Trans-Baikal region. The inhomogeneous velocity structure (according to P - and S - waves) of the upper part of the Earth's crust to the depths of 15–20 km and Moho surface was established. The anomalous mantle with reduced values of the boundary velocity of P - and S-waves (7.8–7.95 km/s and 4.3–4.5 km/s, respectively) was reliably traced within the Baikal rift zone using GSS and seismology data. In the southeastern part of the area (in the central Mongol-Okhotsk orogenic belt and adjacent folded structures of the Trans-Baikal region), a layer of increased P-and S-wave velocity values on was detected the mantle surface at 8.4 ± 0.15 km/s and 4.9 ± 0.05 km/s, respectively. A comparison was made with the materials of other studies.

scholarly journals ANALYSIS OF THE DEEP SEISMIC STRUCTURE AND SEISMICITY OF THE TRANSBAIKALIA (ALONG THE 1-SB PROFILE)

2019 ◽  
Vol 2 (2) ◽  
pp. 224-233
Author(s):  
Victor Solovyev ◽  
Alexander Salnikov ◽  
Viktor Seleznev ◽  
Vladimir Chechelnitsky ◽  
Nadezhda Gilyova ◽  
...  
Keyword(s):  
Rift Zone ◽  
Velocity Structure ◽  
Deep Structure ◽  
Baikal Rift Zone ◽  
Earth’S Crust ◽  
Seismic Structure ◽  
Elastic Parameters ◽  
S Waves ◽  
Close Proximity ◽  
Earth's Crust

An analyzing on the seismicity and the deep structure of Transbaikalia along the 1-SB profile is presented. Determined that areas of high seismicity associated with the blocks of the Earth's crust with a heterogeneous velocity structure. The site of the Baikal rift zone which is located in close proximity to the Muya earthquake (1957, M=7.6) is characterized by increased heterogeneity according to the values of P- and S-waves and of elastic parameters in the Earth’s crust upper part.

scholarly journals Upper mantle of Baikal and Transbaikalia according to the area data of seismological research

2020 ◽  
Vol 2 (1) ◽  
pp. 7-17 ◽  
Author(s):  
Victor Solovyev ◽  
Viktor Seleznev ◽  
Vladimir Chechelnitsky ◽  
Natalya Galyova
Keyword(s):  
Upper Mantle ◽  
Velocity Structure ◽  
Baikal Rift Zone ◽  
Research Area ◽  
Southeastern Part ◽  
Transverse Waves ◽  
S Waves ◽  
New Information ◽  
Seismological Data ◽  
Boundary Velocity

According to the areal interpretation of seismological data from sufficiently strong earth-quakes, new information on the velocity structure of the upper mantle of the Baikal and Trans-Baikal regions is presented. Based on the results of a tomographic interpretation of the travel times of P and S waves from the Mokhorovichich border, maps of the boundary velocities of longitudinal and transverse waves in the Baikal and Transbaikalia, the ratios of the velocities of the P and S waves (Vp/Vs), and the distribution of the Poisson's ratio (σ) are constructed. The boundary velocity in the northwestern, northern, and northeastern parts of the research area (within the Baikal rift zone) according to longitudinal and transversal waves has lower values of 7.80-7.95 km/s and 4.45-4.55 km/s, respectively. In the upper mantle of the southeastern part of the area, the mantle block is about 600x600 km in size with high longitudinal and transversal wave’s velocities of 8.40-8.45 km/s and 4.80-4.85 km/s, respectively, and increased values of Vp/Vs and σ. The assumption of its nature as a plate of eclogites (or eclogite-like rocks) in the region of the Mongol-Okhotsk orogenic belt is justified. The results were compared with materials from other research.

scholarly journals Simulation of seismic waves at the earth's crust (brittle–ductile transition) based on the Burgers model

Solid Earth ◽  
2014 ◽  
Vol 5 (2) ◽  
pp. 1001-1010 ◽  
Author(s):  
J. M. Carcione ◽  
F. Poletto ◽  
B. Farina ◽  
A. Craglietto
Keyword(s):  
Seismic Waves ◽  
In Situ Stress ◽  
Seismic Attenuation ◽  
Earth’S Crust ◽  
S Wave ◽  
Fourier Pseudospectral Method ◽  
Stress Criterion ◽  
Brittle Ductile Transition ◽  
Earth's Crust

Abstract. The earth's crust presents two dissimilar rheological behaviors depending on the in situ stress-temperature conditions. The upper, cooler part is brittle, while deeper zones are ductile. Seismic waves may reveal the presence of the transition but a proper characterization is required. We first obtain a stress–strain relation, including the effects of shear seismic attenuation and ductility due to shear deformations and plastic flow. The anelastic behavior is based on the Burgers mechanical model to describe the effects of seismic attenuation and steady-state creep flow. The shear Lamé constant of the brittle and ductile media depends on the in situ stress and temperature through the shear viscosity, which is obtained by the Arrhenius equation and the octahedral stress criterion. The P and S wave velocities decrease as depth and temperature increase due to the geothermal gradient, an effect which is more pronounced for shear waves. We then obtain the P−S and SH equations of motion recast in the velocity-stress formulation, including memory variables to avoid the computation of time convolutions. The equations correspond to isotropic anelastic and inhomogeneous media and are solved by a direct grid method based on the Runge–Kutta time stepping technique and the Fourier pseudospectral method. The algorithm is tested with success against known analytical solutions for different shear viscosities. A realistic example illustrates the computation of surface and reverse-VSP synthetic seismograms in the presence of an abrupt brittle–ductile transition.

Microearthquake S-wave observations from 0 to 1 km in the Varian well at Parkfield, California

1995 ◽  
Vol 85 (6) ◽  
pp. 1805-1820
Author(s):  
Denis Jongmans ◽  
Peter E. Malin
Keyword(s):  
Fault Zone ◽  
Guided Waves ◽  
Velocity Structure ◽  
San Andreas Fault ◽  
High Gain ◽  
S Wave ◽  
Lateral Velocity ◽  
Wave Amplification ◽  
S Waves ◽  
San Andreas

Abstract High-gain three-component seismometers from 0- to 1-km deep along the Varian A-1 well at Parkfield, California, were used to record the waveforms of nearby microearthquakes. Despite being in the thick Tertiary sediments of the Parkfield Syncline, the S-wave amplification at this site is only about a factor of 3. The spectral content and spectral ratios of S waves along the well show that the average Qs in the top 1 km at this site is 37, with the Qs in different subintervals varying between 8 and 65. Based on initial S-wave polarizations, a complex S-wave velocity structure must exist at and below the Varian site. This structure appears to include position-dependent anisotropy as well as steep lateral velocity gradients. At a depth of 1 km, S-wave splitting parallel and normal to the San Andreas fault zone is consistently observed. This splitting scales at roughly 0.01 sec/km. Subsequent to the split S waves, the particle motion seems to be controlled by event focal mechanism. Above 1 km, the upgoing S waves attenuate and change directions of polarization, with a new splitting rate of 0.1 sec/km. Uniquely, for some events on the San Andreas fault immediately below the Varian site, large, post-S-wave signals with normal dispersion are present. We propose that these phases are fault-zone guided waves channeled from the San Andreas fault to the Varian site along the Gold Hill fault.

DEPTH STRUCTURE FEATURES OF THE EASTERN STANOVOY FRAGMENT OF THE 8-DV GEOLOGICALGEOPHYSICAL SURVEY – BASE LINE (ACCORDING TO THE DSS DATA)

2020 ◽  
pp. 29-39
Author(s):  
V. M. Soloviev ◽  
◽  
A. S. Salnikov ◽  
V. S. Seleznev ◽  
T. V. Kashubina ◽  
...  
Keyword(s):  
Earth’S Crust ◽  
Base Line ◽  
Seismic Structure ◽  
Fold Belt ◽  
Longitudinal Waves ◽  
Surface Change ◽  
Central Asian ◽  
Tectonic Zones ◽  
Earth's Crust ◽  
Dss Data

The materials of deep seismic operations on the Vostochno-Stanovoy fragment of the survey base geophysical profile 8-DV within large tectonic zones – the Selengino-Stanovoy and Amur fold regions of the Central Asian fold belt are presented. It is shown that longitudinal waves from the boundaries in the earth’s crust and the surface of Mohorovichich were recorded from explosions on a 700-kilometer geophysical profile. An inhomogeneous structure was established according to the data of longitudinal waves of the upper part of the earth’s crust to depths of 15–20 km and the surface of Mohorovichich. In general, the thickness of the earth’s crust at the profile is 37–42 km; the effective velocities of longitudinal waves in the crust and refractor ones along the mantle surface change at the profile, respectively, from 6.35 to 6.5 km/s and from 7.9 to 8.5 km/s. The results obtained are discussed and established features of the seismic structure are compared with the tectonics of the region and materials from other studies.

scholarly journals Stress-strain state of the earth’s crust of the Central Asian mountain belt: distant effect of the tectonic impact of the Indo-Eurasian collision

2021 ◽  
Vol 929 (1) ◽  
pp. 012003
Author(s):  
M M Buslov
Keyword(s):  
Central Asia ◽  
Sedimentary Basins ◽  
Tien Shan ◽  
Earth’S Crust ◽  
High Mountain ◽  
Mountain Ranges ◽  
Central Asian ◽  
Sayan Region ◽  
Earth's Crust ◽  
Cenozoic Sediments

Abstract In recent decades, extensive geological, geophysical and geochronological data have been obtained that characterize in detail the results of the distant tectonic impact of the Indo-Eurasian collision on the lithosphere of Central Asia, which led to the formation of the mountain systems of the Pamirs, Tien Shan, Altai-Sayan region and Transbaikalia from the Late Paleogene (about 25 million years ago). It has been established that the formation of the structure of Central Asia occurred as a result of the transmission of deformations from the Indo-Eurasian collision over long distances according to the “domino principle” through the rigid structures of Precambrian microcontinents located among the Paleozoic-Mesozoic folded belts. The study of peneplain surfaces deformed into simple folds on high-mountain plateaus surrounded by rugged mountain ranges made it possible to reveal the parameters of the deformations of the earth’s crust, the interrelationship of the formation of relief and sedimentary basins. Apatite track dating data, structural and stratigraphic analyses of Late Cenozoic sediments in the basins prove a period of intense tectonic activation the entire lithosphere of Central Asia from the Indian continent to the Siberian platform starting from the Pliocene (about 3.5 million years). As a result of reactivation of the heterogeneous basement of Central Asia, high seismicity was manifested, which is concentrated mainly along the border of the microcontinents (Central Tianshan, Junggar and Tuva-Mongolian) and the Siberian craton, as well as in the zones of articulation of regional faults.

scholarly journals Towards а design of new generation digital seismic seabed seismographs – current state and future outlook

2019 ◽  
pp. 87-101
Author(s):  
D. A. Il’inskiy ◽  
A. A. Ginzburg ◽  
V. V. Voronin ◽  
O. Yu. Ganzha ◽  
A. B. Manukin ◽  
...  
Keyword(s):  
Black Sea ◽  
Sedimentary Cover ◽  
Earth’S Crust ◽  
Seismic Exploration ◽  
The Black Sea ◽  
Reference Frequency ◽  
S Wave ◽  
Russian Sector ◽  
Earth's Crust ◽  
New Generation

The paper presents the comparative characteristics of self-pop-up digital seabed seismometers that have been developed since the early 2000s. The requirements for the main technical characteristics that should be considered for developing the new-generation of self-pop-up seabed seismometers have been proposed. The microcontroller and reference frequency generator are the key parts for a seabed seismometer design. The paper provides the development results of these key components, which are essential for the seismometer performance (power consumption and functionality). A draft proposal for seabed seismic exploration project in the Russian sector of the Black Sea solving the current actual geological problems is presented. Implementation of the project will contribute to determination of the crystalline basement depth within the Shatsky ridge and the Tuapse depression; detection of P and S wave velocities in the lower part of sedimentary cover and in the basement, and to the refinement of the Earth’s crust thickness. The extension of regional seabed seismic lines from the Turkish to the Russian sector of the Black Sea will give the scientists a clearer picture of the Earth’s crust structure over the whole east Black Sea basin. The results of seabed studies will verify and improve the results of the Black Sea 2011 towed-streamer survey (with 10 km streamer) on the sedimentary cover structure and the Earth’s crust.

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