Feasibility of determiningQof near‐surface materials from Rayleigh waves

2001 ◽  
Author(s):  
Jianghai Xia ◽  
Richard D. Miller ◽  
Choon B. Park ◽  
Julian Ivanov
Keyword(s):  
Rayleigh Waves ◽  
Near Surface ◽  
Surface Materials

Determining Q of near-surface materials from Rayleigh waves

2002 ◽  
Vol 51 (2-4) ◽  
pp. 121-129 ◽  
Author(s):  
Jianghai Xia ◽  
Richard D Miller ◽  
Choon B Park ◽  
Gang Tian
Keyword(s):  
Rayleigh Waves ◽  
Near Surface ◽  
Surface Materials

Surface-Wave Simulation for the Continuously Moving Seismic Sources

2021 ◽  
Author(s):  
Yuefeng Yan ◽  
Chengyu Sun ◽  
Tengfei Lin ◽  
Jiao Wang ◽  
Jidong Yang ◽  
...  
Keyword(s):  
Rayleigh Waves ◽  
Frequency Dispersion ◽  
Dispersion Curves ◽  
Velocity Estimation ◽  
Surface Velocity ◽  
Seismic Sources ◽  
Near Surface ◽  
Moving Source ◽  
Source Data ◽  
Doppler Effects

Abstract In exploration and earthquake seismology, most sources used in subsurface structure imaging and rock property estimation are fixed in certain positions. Continuously moving seismic sources, such as vehicles and the metro, are one kind of important passive sources in ambient noise research. Commonly, seismic data acquisition and processing for moving sources are based on the assumption of simple point passive sources, and the dispersion curve inversion is applied to constrain near-surface velocity. This workflow neglects the Doppler effects. Considering the continuously moving properties of the sources, we first derive the analytical solution for the Rayleigh waves excited by heavy vehicles and then analyze their Doppler effects and dispersion curves. We observe that the moving source data have the Doppler effect when compared with the changes in the frequency of the source intensity, but this effect does not affect the frequency dispersion of Rayleigh waves. The dispersion curves computed for moving source records are consistent with the analytical dispersion solutions, which provide a theoretical foundation for velocity estimation using moving source data.

Propagation of dispersed compressional and Rayleigh waves on the Texas coastal plain

Geophysics ◽  
1983 ◽  
Vol 48 (1) ◽  
pp. 27-35 ◽  
Author(s):  
Joseph Ebeniro ◽  
Clark R. Wilson ◽  
James Dorman
Keyword(s):  
Coastal Plain ◽  
Rayleigh Waves ◽  
Poisson Ratio ◽  
Normal Modes ◽  
Compressional Wave ◽  
Unconsolidated Sediments ◽  
Near Surface ◽  
Shallow Subsurface ◽  
Strong Surface ◽  
Group Velocities

During a refraction profile on the Texas coastal plain, a strong surface wave with predominant frequencies between 2 and 10 Hz and group velocities near 1.9 km/sec was observed to ranges as great as 64 km. This dispersed wave, with velocities near the compressional wave speed of near‐surface sediments, corresponds to the “leaky” compressional or PL wave. PL dispersion can be predicted from the theory of the normal modes of a layered liquid medium. Efficient propagation of the PL wave is related to the high Poisson ratio of the unconsolidated sediments in the shallow subsurface, and additional examples from the published literature show that the PL wave is commonly excited by shallow sources both on land and offshore. In addition to the PL waves, dispersed waves with group velocities between 0.3 and 0.7 km/sec were observed at ranges less than 10 km. These are identified as Rayleigh waves (LR). Smoothly varying P and S velocity structures for the upper 1 km are obtained by fitting theoretical dispersion curves to the observed PL and LR data.

scholarly journals To the possibility of increasing the efficiency of powerful vibroseismic sources

2019 ◽  
Vol 489 (1) ◽  
pp. 80-83
Author(s):  
A. L. Sobisevich ◽  
R. A. Zhostkov
Keyword(s):  
Parametric Study ◽  
Rayleigh Waves ◽  
Seismic Sources ◽  
Design Features ◽  
Near Surface ◽  
New Approaches ◽  
The Earth ◽  
Numerical Parametric Study

A numerical parametric study of the scattering features of arising from the operation of a vibroseis source Rayleigh waves on near-surface inhomogeneities (seismic barriers) has been performed. In order to find new approaches to the problem of global sensing of the Earth with powerful vibro-seismic sources, the conditions for increasing the efficiency of the emission of volumetric waves due to the design features of seismic barriers were analyzed.

Chemical Weathering on Venus

2019 ◽  
Author(s):  
Mikhail Zolotov
Keyword(s):  
Chemical Weathering ◽  
Uncertain Data ◽  
Chemical Kinetic ◽  
Gas Content ◽  
Atmospheric Gases ◽  
Emission Data ◽  
Near Surface ◽  
Fe Oxides ◽  
Basaltic Composition ◽  
Surface Materials

Chemical and phase compositions of the surface of Venus could reflect a history of gas–rock and fluid–rock interactions, recent and past climate changes, and a loss of water from the Earth’s sister planet. The concept of chemical weathering on Venus through gas–solid type reactions was established in the early 1960s after the discovery of the hot and dense CO2-rich atmosphere of the planet, inferred from Earth-based and Mariner 2 radio emission data. Initial models suggested carbonation, hydration, and oxidation of exposed igneous rocks and a control (buffering) of atmospheric gases by solid–gas type chemical equilibria in the near-surface rocks. Carbonates, phyllosilicates and Fe oxides were considered likely secondary minerals. From the late 1970s onward, measurements of trace gases in the sub-cloud atmosphere by the Pioneer Venus and Venera entry probes and by Earth-based infrared spectroscopy challenged the likelihood of hydration and carbonation. The atmospheric H2O gas content appeared to be low enough to allow the stable existence of H2O-bearing and a majority of OH-bearing minerals. The concentration of SO2 gas was too high to allow the stability of Ca-rich carbonates and silicates with respect to sulfatization to CaSO4. In the 1980s, the detection of an elevated bulk S content at the Venera and Vega landing sites suggested ongoing consumption of atmospheric SO2 to surface sulfates. The supposed composition of the near-surface atmosphere implied oxidation of ferrous minerals to Fe oxides, magnetite and hematite, consistent with the infrared reflectance of surface materials. The likelihood of sulfatization and oxidation has been illustrated in modeling experiments in simulated Venus’ conditions. The morphology of Venus’ surface suggests contact of atmospheric gases with hot surface materials of mainly basaltic composition during the several hundreds of millions years since a global volcanic/tectonic resurfacing. Some exposed materials could have reacted at higher and lower temperatures in a presence of diverse gases at different altitudinal, volcanic, impact, and atmospheric settings. On highly deformed tessera terrains, more ancient rocks of unknown composition may reflect interactions with putative water-rich atmospheres and even aqueous solutions. Geological formations rich in salt, carbonate, Fe oxide, or silica will indicate past aqueous processes. The apparent diversity of affected solids, surface temperatures, pressures, and gas/fluid compositions throughout Venus’ history implies multiple signs of chemical alterations that remain to be investigated. The current understanding of chemical weathering is limited by the uncertain composition of the deep atmosphere, by the lack of direct data on the phase and chemical composition of surface materials, and by the uncertain data on thermodynamics of minerals and their solid solutions. In preparation for further atmospheric entry probe and lander missions, rock alteration could be investigated through chemical kinetic experiments and calculations of solid-gas/fluid equilibria to constrain past and present processes.

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