scholarly journals Results and prospects of seismological observations in the central part of the Baikal rift

2021 ◽  
Vol 3 (4) ◽  
pp. 38-57
Author(s):  
Tsyren Tubanov ◽  
Petr Predein ◽  
Larisa Tcydypova ◽  
Darima Sanzhieva ◽  
Natalia Radziminovich ◽  
...  
Keyword(s):  
Seismic Waves ◽  
Baikal Region ◽  
Wave Attenuation ◽  
Receiver Function ◽  
Local Network ◽  
Vibration Source ◽  
Lake Baikal Region ◽  
Instrumental Observations ◽  
Receiver Function Method ◽  
Academy Of Sciences

This article reports the results of detailed seismological observations in the Central Baikal region conducted by the local network of seismological stations of the Buryat Division of the Geophysical Survey of the Russian Academy of Sciences. The local network was created in the 1990s. A crucial feature of the network is the combination of seismic monitoring both in the passive mode (the study of natural seismicity) and in the active mode, with a controlled vibration source of seismic waves. The study area covers the Lake Baikal region and adjacent territories characterized by high seismic activity. Here occurred several catastrophic earthquakes including the strongest one during the period of instrumental observations – the Middle Baikal’1959 earthquake. Recently here occurred the Kudarinsky earthquake on December 9, 2020 with mb=5.4. For more than twenty years the network of observations has been expanding, the equipment has been upgrading. A significant amount of seismo-logical material has been accumulated. Broadband data was processed by the receiver function method. The Moho and the lithosphere-asthenosphere boundaries for stations of the network are determined. Shear seismic wave attenuation characteristics are obtained and the possibility of energy classification of Baikal earthquakes by coda-waves total oscillations is shown.

The first record of Gyalideopsis helvetica (Graphidaceae, lichenized Ascomycota) for Russia from the southern part of Lake Baikal Region

2015 ◽  
Vol 49 ◽  
pp. 282-288 ◽  
Author(s):  
I. N. Urbanavichene
Keyword(s):  
Lake Baikal ◽  
Baikal Region ◽  
First Record ◽  
Identification Key ◽  
Lake Baikal Region ◽  
First Time

Until recently only two species of Gyalideopsis (G. piceicola and G. alnicola) were known from very few localities in Russia. Gyalideopsis helvetica is reported for the first time for Russia from the southern part of Baikal area (KhamarDaban Range, Baikalsky Zapovednik). Description of the collected specimen and its comparison with the literature data are provided; morphology, ecology and distribution of G. helvetica are discussed. The hyphophores of G. helvetica are recorded and described for the first time. An identification key to Gyalideopsis species known in Russia is provided.

An improved method to estimate Q based on the logarithmic spectrum of moving peak points

2019 ◽  
Vol 7 (2) ◽  
pp. T255-T263 ◽  
Author(s):  
Yanli Liu ◽  
Zhenchun Li ◽  
Guoquan Yang ◽  
Qiang Liu
Keyword(s):  
Seismic Waves ◽  
Wave Attenuation ◽  
Real Data ◽  
Peak Frequency ◽  
Seismic Reflection Data ◽  
The Real ◽  
Time Frequency ◽  
Reflection Data ◽  
Text Filtering ◽  
The Impact

The quality factor ([Formula: see text]) is an important parameter for measuring the attenuation of seismic waves. Reliable [Formula: see text] estimation and stable inverse [Formula: see text] filtering are expected to improve the resolution of seismic data and deep-layer energy. Many methods of estimating [Formula: see text] are based on an individual wavelet. However, it is difficult to extract the individual wavelet precisely from seismic reflection data. To avoid this problem, we have developed a method of directly estimating [Formula: see text] from reflection data. The core of the methodology is selecting the peak-frequency points to linear fit their logarithmic spectrum and time-frequency product. Then, we calculated [Formula: see text] according to the relationship between [Formula: see text] and the optimized slope. First, to get the peak frequency points at different times, we use the generalized S transform to produce the 2D high-precision time-frequency spectrum. According to the seismic wave attenuation mechanism, the logarithmic spectrum attenuates linearly with the product of frequency and time. Thus, the second step of the method is transforming a 2D spectrum into 1D by variable substitution. In the process of transformation, we only selected the peak frequency points to participate in the fitting process, which can reduce the impact of the interference on the spectrum. Third, we obtain the optimized slope by least-squares fitting. To demonstrate the reliability of our method, we applied it to a constant [Formula: see text] model and the real data of a work area. For the real data, we calculated the [Formula: see text] curve of the seismic trace near a well and we get the high-resolution section by using stable inverse [Formula: see text] filtering. The model and real data indicate that our method is effective and reliable for estimating the [Formula: see text] value.

Persistent Organochlorine Residues in Air, Water, Sediments, and Soils from the Lake Baikal Region, Russia

1995 ◽  
Vol 29 (3) ◽  
pp. 792-801 ◽  
Author(s):  
Hisato. Iwata ◽  
Shinsuke. Tanabe ◽  
Kozo. Ueda ◽  
Ryo. Tatsukawa
Keyword(s):  
Lake Baikal ◽  
Baikal Region ◽  
Persistent Organochlorine ◽  
Lake Baikal Region

Assessing the acidification risk in the Lake Baikal region

2006 ◽  
Vol 22 (1) ◽  
pp. 1-11 ◽  
Author(s):  
M. Yu. Semenov ◽  
T. V. Khodzher ◽  
V. A. Obolkin ◽  
V. M. Domysheva ◽  
L. P. Golobokova ◽  
...  
Keyword(s):  
Lake Baikal ◽  
Baikal Region ◽  
Lake Baikal Region

Seismic wave attenuation due to fluid pressure diffusion at the mesoscopic scale: an experimental and numerical study

2021 ◽  
Author(s):  
Samuel Chapman ◽  
Jan V. M. Borgomano ◽  
Beatriz Quintal ◽  
Sally M. Benson ◽  
Jerome Fortin
Keyword(s):  
Seismic Wave ◽  
Seismic Waves ◽  
Wave Attenuation ◽  
Fluid Pressure ◽  
Fluid Distribution ◽  
Mesoscopic Scale ◽  
Seismic Wave Attenuation ◽  
X Ray ◽  
Pressure Diffusion ◽  
Attenuation And Dispersion

<p>Monitoring of the subsurface with seismic methods can be improved by better understanding the attenuation of seismic waves due to fluid pressure diffusion (FPD). In porous rocks saturated with multiple fluid phases the attenuation of seismic waves by FPD is sensitive to the mesoscopic scale distribution of the respective fluids. The relationship between fluid distribution and seismic wave attenuation could be used, for example, to assess the effectiveness of residual trapping of carbon dioxide (CO2) in the subsurface. Determining such relationships requires validating models of FPD with accurate laboratory measurements of seismic wave attenuation and modulus dispersion over a broad frequency range, and, in addition, characterising the fluid distribution during experiments. To address this challenge, experiments were performed on a Berea sandstone sample in which the exsolution of CO2 from water in the pore space of the sample was induced by a reduction in pore pressure. The fluid distribution was determined with X-ray computed tomography (CT) in a first set of experiments. The CO2 exosolved predominantly near the outlet, resulting in a heterogeneous fluid distribution along the sample length. In a second set of experiments, at similar pressure and temperature conditions, the forced oscillation method was used to measure the attenuation and modulus dispersion in the partially saturated sample over a broad frequency range (0.1 - 1000 Hz). Significant P-wave attenuation and dispersion was observed, while S-wave attenuation and dispersion were negligible. These observations suggest that the dominant mechanism of attenuation and dispersion was FPD. The attenuation and dispersion by FPD was subsequently modelled by solving Biot’s quasi-static equations of poroelasticity with the finite element method. The fluid saturation distribution determined from the X-ray CT was used in combination with a Reuss average to define a single phase effective fluid bulk modulus. The numerical solutions agree well with the attenuation and modulus dispersion measured in the laboratory, supporting the interpretation that attenuation and dispersion was due to FPD occurring in the heterogenous distribution of the coexisting fluids. The numerical simulations have the advantage that the models can easily be improved by including sub-core scale porosity and permeability distributions, which can also be determined using X-ray CT. In the future this could allow for conducting experiments on heterogenous samples.</p>

A simple and general macroscopic model for local-deformation effects in fluid-saturated porous rock

2019 ◽  
Vol 220 (3) ◽  
pp. 1893-1903
Author(s):  
Wubing Deng ◽  
Igor B Morozov
Keyword(s):  
Material Properties ◽  
Seismic Waves ◽  
Wave Attenuation ◽  
Spatial Scales ◽  
Local Deformation ◽  
Macroscopic Model ◽  
Porous Rock ◽  
Specific Flow ◽  
Frequency Independent ◽  
Consistent Manner

SUMMARY Wave-induced fluid flows (WIFF) can be viewed as cases of broader local-deformation (LD) phenomena and represent the principal causes of seismic-wave attenuation in fluid-saturated porous rock. Most existing WIFF models refer to greatly simplified microstructures and specific flow patterns, such as planar divergent flows within thin cracks (squirt flows, SF) or flows within patchy-saturation zones. However, such microstructures represent only idealized mathematical models that may be impossible to consistently identify within a given rock. At the same time, most details of such microstructures are insignificant for seismic waves, which are only sensitive to averaged properties of the medium. To perform microstructure-independent modelling of LD effects, we develop a simple yet general approach based entirely on a macroscopic local-deformation variable. This variable is broadly analogous to Biot's fluid content and is illustrated for two specific microstructural models. The macroscopic model is Biot-consistent and uses only time- and frequency-independent material properties. Both local and global (Biot's) pore flows and all types of waves and deformations are explained in a rigorous and consistent manner. The model allows constraining a minimal set of material properties responsible for all observed elastic and anelastic effects in porous rock. Because of making no assumptions about the microstructures and their spatial scales, this approach should comprise at least some of the existing WIFF models. In particular, this model accurately reproduces all attenuation and velocity dispersion spectra predicted by a broadly used SF model. The model also contains effects not considered previously, such as bulk viscosity of pore fluid and viscous coupling between the rock frame and fluid-filled pores. The model offers straightforward extensions to multiple porosities and cases of viscous fluids in primary pores. Based on the resulting differential equations, physically consistent schemes for numerical modelling of seismic wavefields can be developed for porous rock with arbitrary LD effects.

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