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In recent years, the State Grid of China has placed significant emphasis on the monitoring of noise in substations, driven by growing environmental concerns. This paper presents a substation noise monitoring system designed based on an end-network-cloud architecture, aiming to acquire and analyze substation noise, and report anomalous noise levels that exceed national standards for substation operation and maintenance. To collect real-time noise data at substations, a self-developed noise acquisition device is developed, enabling precise analysis of acoustic characteristics. Moreover, to subtract the interfering environmental background noise (bird/insect chirping, human voice, etc.) and determine if noise exceedances are originating from substation equipment, an intelligent noise separation algorithm is proposed by leveraging the convolutional time-domain audio separation network (Conv-TasNet), dual-path recurrent neural network (DPRNN), and dual-path transformer network (DPTNet), respectively, and evaluated under various scenarios. Experimental results show that (1) deep-learning-based separation algorithms outperform the traditional spectral subtraction method, where the signal-to-distortion ratio improvement (SDRi) and the scale-invariant signal-to-noise ratio improvement (SI-SNRi) of Conv-TasNet, DPRNN, DPTNet and the traditional spectral subtraction are 12.6 and 11.8, 13.6 and 12.4, 14.2 and 12.9, and 4.6 and 4.1, respectively; (2) DPTNet and DPRNN exhibit superior performance in environment noise separation and substation equipment noise separation, respectively; and (3) 91% of post-separation data maintains sound pressure level deviations within 1 dB, showcasing the effectiveness of the proposed algorithm in separating interfering noises while preserving the accuracy of substation noise sound pressure levels. [ABSTRACT FROM AUTHOR]

Reservoir in-situ stress is crucial in oil and gas exploration and development. With the transitional shale as the research object, the ultrasonic transmission test and uniaxial compression test of rock samples from different sampling angles were performed. Further, the transversely isotropic in-situ stress logging calculation method for transitional shale reservoirs was established based on the transversely isotropic constitutive relationship. Finally, the in-situ stress profile of the transitional shale reservoir in the study area was analyzed, and the reliability of the results was verified. The results indicated that the mechanical characteristics of rock and its acoustic velocity varied significantly depending on the sample angle, with some regularity in the changes between vertical and horizontal mechanical properties. The logging profile revealed that the transverse Young modulus was greater than the vertical, and the vertical Poisson's ratio was typically greater than the transverse. The suggested transversely isotropic model performed better than the conventional in-situ stress model at predicting the in-situ stress of transitional shale reservoirs, with an error of less than 2%. This demonstrated the applicability of the model's in-situ stress calculation of the transitional shale reservoir. [ABSTRACT FROM AUTHOR]

The conventional technique for positioning seafloor geophones in ocean bottom seismic exploration encounters several challenges, including the significant impact of outliers on positioning results, underutilization of high-precision observations, and low efficiency in real-time data processing. These issues inevitably affect the quality of seismic exploration outcomes. To address these challenges and enhance the accuracy of geophone positioning, this paper proposes a rigorous real-time acoustic positioning method for geophones based on sequential adjustment and Baarda's outlier detection approach. The proposed method comprises three key steps: grouping the original acoustic observations, constructing the intra-group acoustic positioning model, and synthesizing the positioning results across the different groups. The validity and practicality of this approach are confirmed through a simulation experiment as well as the field experiment conducted in the Bohai Sea, China. The results demonstrate that the proposed method effectively eliminates outliers in the original observations and maximizes the utilization of high-quality observations. Compared to traditional acoustic positioning methods, it significantly reduces positioning errors from meters to decimeters, and in some cases can achieve centimeter-level precision. When the sound velocity profile in the operating sea area is measured, the method can attain the posterior standard deviation at the millimeter level and positioning errors within 10 cm. When the sound velocity profile is unknown, the method can achieve the posterior standard deviation at centimeter-level and positioning errors of approximately 20 cm. [ABSTRACT FROM AUTHOR]

The shale of the Wufeng–Longmaxi formation in the Sichuan Basin is the preferred layer for shale gas exploration in China, and its petrophysical characteristics are the key to geological and engineering sweet spot prediction. However, the characteristics and impact mechanisms of its acoustic wave velocity and elastic anisotropy are currently unclear. In this paper, the Wufeng–Longmaxi shale is taken as the research object, and the P-wave and S-wave velocities of the samples are tested under the loading and unloading processes of confining pressure. The stress sensitivity variations in parameters such as wave velocity, wave velocity ratio, and anisotropy are discussed. P-wave and S-wave anisotropy parameters are correlated under different pressure conditions. X-ray diffraction, casting thin sections, scanning electron microscopy, micron CT scanning, and other analytical techniques are used to explore the mechanisms of stress sensitivity of elastic parameters. The research results indicate that: (1) the acoustic velocities of samples from different angles are V90° > V45° > V0°, and there is a positive correlation between the wave velocity and the confining pressure. After unloading the confining pressure, irreversible plastic deformation occurs due to the closure of some microfractures in the rock core, causing the wave velocity to be higher than the initial value. (2) The stress sensitivity coefficient of the P-wave (The mean is 3.00 m·s−1·MPa−1) is higher than that of the S-wave (the mean is 1.23 m·s−1·MPa−1), and the stress sensitivity coefficient of the compacted stage (the mean is 3.02 m·s−1·MPa−1) is higher than that of the elastic stage (the mean is 1.21 m·s−1·MPa−1). (3) The anisotropy of the P-wave and S-wave is negatively correlated with the confining pressure. When the confining pressure is loaded to 65 MPa, the change rate of the P-wave anisotropy coefficient is 23%, and its stress sensitivity is higher than that of S-wave anisotropy coefficient (the change rate is 13.7%). After unloading the confining pressure, the degree of anisotropy is reduced due to the closure of some microfractures. The empirical formula of P-wave and S-wave anisotropy parameters under different pressures is established through linear regression, which can provide a reference for mutual predictions. (4) The variation in wave velocity anisotropy with stress can be divided into stress and material anisotropy, which are related to the directional arrangement of microfractures and clay minerals, respectively. The quantitative characterization of shale anisotropy can be realized by evaluating the development degree of reservoir fractures and mineral components, providing a reference for logging interpretations, sweet spot prediction, and fracturing construction of shale gas reservoirs. [ABSTRACT FROM AUTHOR]

Due to the complicated interference sources and low signal-to-noise ratio of seismic records, conventional seismic inversion methods are difficult to accurately identify shale gas reservoirs with a thickness of less than 10 m. This presents great challenges to shale gas exploration and development in China. Seismic phase-controlled nonlinear stochastic inversion (SPCNSI) is related to the heterogeneity of underground media. With the constraints of the stratigraphic sequence or seismic facies models, the minimum value between the seismic model and seismic record can be solved through iterative processes. Based on the solved acoustic velocity in formation, the constraints for SPCNSI can be formed with the matching relationship between target layers and different sequences in three-dimensional space. The prediction resolution of an unconventional reservoir can be effectively improved by combining logging, geological and seismic information. The method is suitable for predicting thin shale gas reservoirs in complex geological structures. In this study, SPCNSI was developed to predict the thin-layer marine shale gas reservoir in the southeast of Chongqing; the horizontal and vertical distribution characteristics were proven in the Longmaxi Formation and the Wufeng Formation; thin layers with a thickness of less than 7 m were also discovered. According to the results, three sets of potential development areas were determined by the inversion method, and the accuracy and reliability of the method were verified by logging and productivity testing. [ABSTRACT FROM AUTHOR]

In this paper, a Comprehensive Diagram Method (CDM) for a Multi-Layer Perceptron Neuron Network (MLPNN) is proposed to realize natural gas energy metering using temperature, pressure, and the speed of sound from an ultrasonic flowmeter. Training and testing of the MLPNN model were performed on the basis of 1003 real data points describing the compression factors (Z-factors) and calorific values of the three main components of natural gas in Sichuan province, China. Moreover, 20 days of real tests were conducted to verify the measurements' accuracy and the adaptability of the new intelligent method. Based on the values of the Mean Relative Errors and the Root Mean Square errors for the learning and test errors calculated on the basis of the actual data, the best-quality MLP 3-5-1 network for the metering of Z-factors and the new CDM methods for the metering of calorific values were experimentally selected. The Bayesian regularized MLPNN (BR-MLPNN) 3-5-1 network showed that the Z-factors of natural gas have a maximum relative error of −0.44%, and the new CDM method revealed calorific values with a maximum relative error of 1.90%. In addition, three local tests revealed that the maximum relative error of the daily cumulative amount of natural gas energy was 2.39%. [ABSTRACT FROM AUTHOR]

Experimental study of logging petrophysical parameters is very important for the establishment of logging evaluation model of coalbed methane reservoir. The acoustic and resistivity measurements of coal rock samples taken from the southern Qinshui Basin in China were measured under dry and saturated conditions of different salinity solutions. The variation laws of acoustic velocity and waveform with saturated salinity were analyzed. The changes of resistivity with temperature and pressure conditions were also analyzed. With the increase in salinity, acoustic velocity showed parabolic attenuation characteristics. The fluid content of coal samples can be judged by the acoustic wave. The waveform of dry coal sample presented multiple excitation state, and the waveform had larger fluctuation and smaller amplitude. The waveform of saturated salinity coal sample presented stable and smooth fluctuation characteristics. The resistivity of coal rock decreased exponentially with the increase in pressure. The property of fluid in pores can be judged by the sensitivity of resistivity of coal rock to temperature. [ABSTRACT FROM AUTHOR]

Copyright of Coal Geology & Exploration is the property of Xian Research Institute of China Coal Research Institute and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

The Sichuan Basin in south-western China is rich in shale oil in the Jurassic strata. Due to its complex geological characteristics, reservoir identification using current log-constrained seismic inversion methods is difficult. Characteristics of the shale oil reservoirs were tested on the basis of the petrophysical experimentation of core samples from the said strata. Thin sections and logging data analysis showed the influencing factors on petrophysical characteristics and clarified the sensitive geophysical parameters for reservoir identification. The Da'anzhai Member reservoirs were determined to have high acoustic velocities, V p/ V s ratios and Young's moduli, and low Poisson's ratios. Several geological factors have influenced the petrophysical properties of the reservoirs. The Da'anzhai Member reservoirs are characterized by a low content of clay minerals and the development of fractures and laminae. The presence of clay minerals caused general high acoustic velocities of the reservoirs; the presence of fractures and laminae in high-quality reservoirs results in a decrease of the acoustic velocities. Therefore, the relatively low value against the background of high acoustic velocity can be used as the criteria for high-quality reservoirs. Poisson's ratio is obviously different in reservoirs and non-reservoirs. When it is <0.269, the reservoirs can be fully identified. In addition, the combination of the Lame constant and shear modulus (λ > 25.277 and μ > 20.72 GPa), P-wave and S-wave velocity (V p > 4967 and V s > 2781 m s−1), wave impedance and V p/ V s ratio (AI > 13.319 g · cm3 · km · s−1 and V p/ V s > 1.792) can also provide references for reservoir identification. [ABSTRACT FROM AUTHOR]

The velocity sections and acoustic parameters of the sedimentary cover in the Central (Japan), Yamato (Honshu), and Tsushima basins, and the Kita–Yamato Trough of the Sea of Japan, as well as the rocks of the basement and the Cenozoic cover of the submarine Yamato Rise were studied. A comparative analysis of similar parameters of the Cenozoic basins in the South China and East China marginal seas was performed. The relationship between the acoustic properties (P-wave velocity, Vp) of the basal horizons and the age of the Cenozoic cover in the above basins was analyzed. The values of Vp = 3.0–3.6 km/s have been validated as the acoustic parameter of Paleocene–Eocene sedimentary strata. According to the studies we performed, the basal layers in the supposed depocenters of the Japan basins (Central, Yamato, and Tsushima) have Vp = 3.0–3.3 km/s, which indicates the Paleocene–Eocene age of the onset of their formation. [ABSTRACT FROM AUTHOR]

Based on a substantial number of seabed sediment samples and corresponding acoustic characteristic and physical property test data collected in the continental shelf area of the northwestern South China Sea, this study employed a sound speed ratio correction model to analyze the correlation between the sound speed ratio of seabed sediments and parameters such as porosity, density, mean grain size, and water content. This study resulted in the development of both single-parameter and double-parameter empirical formulas for the sound speed ratio of seabed sediments in this marine region. The determination coefficients (r2) for the single-parameter empirical formulas based on physical properties, excluding the mean grain size (r2 ≤ 0.75), were all above 0.78, indicating a strong correlation. Additionally, the fitting curve at 100 kHz was slightly greater than that at 50 kHz, consistent with the acoustic dispersion characteristics of sediments. To assess the applicability of the empirical formulas to different maritime areas, the formulas derived from the South Yellow Sea, East China Sea, and South China Sea were compared with those of the study area. The results indicated that the empirical formulas for the sound speed ratio established in this study have general applicability, especially for sediments with low porosity, high density, and low mean grain size. In addition, the determination coefficient of the dual-parameter empirical formula for the sound speed ratio–porosity–mean grain size is superior to that of the single-parameter empirical formula for the sound speed ratio–mean grain size. Through comparative studies with other marine areas, it was found that there are certain differences in the relationships between porosity and mean grain size established in different marine areas. Therefore, based on the rough sphere model, this study transforms the GS model into a single-parameter model built on either porosity or mean grain size. The error analysis results indicate that the single-parameter GS model has a smaller error than the measured data. However, the GS model controlled by a single parameter performs poorly compared to the predicted curves of the sound speed ratio–porosity and the sound speed ratio–mean grain size fitted in this study. This discrepancy may be attributed to the fact that the input parameters of the GS model are reference values, emphasizing the need for further research to determine suitable input parameters for the GS model in this marine area. • The empirical equations for the sound speed ratio were developed in this study in different marine regions. • The established empirical equations for the study area were compared with those for the South Yellow Sea, East China Sea, and other marine regions. • This study compared the empirical equations with the grain shearing (GS) theoretical model. [ABSTRACT FROM AUTHOR]

Cracks and pores coexist in carbonate reservoirs, and this complex pore structure has a significant impact on acoustic and resistivity logging. Making full use of acoustic and electrical well logging data can help to identify carbonate gas reservoirs. First, this paper studies the controlling effects of different lithologies on the acoustic velocity according to the elastic theory of porous and fractured media based on joint acoustic-resistivity rock physics measurement experiments. At the same time, a theoretical gas-bearing reservoir identification template is established based on acoustic experimental data, and the gas-bearing reservoir identification template is used to qualitatively identify a gas reservoir. Then, the empirical relationship between the acoustic velocity and resistivity is derived based on the Archie equation. It is found that the formation P-wave velocity and resistivity have a power function relationship in the research area. Based on the above research, a quantitative identification template for gas-bearing reservoirs is established. The case study has verified the reliability of the gas-bearing carbonate reservoir identification method based on the above two methods. [ABSTRACT FROM AUTHOR]

Accurate detection of void defects in ballastless track structures has become a core problem that needs urgent resolution for the maintenance and repair of high-speed railway (HSR) line structures in China. In this study, the root mean squaresynthetic aperture focusing technique (RMS-SAFT) ultrasound imaging method, which is suitable for the void defects of multi-layer structures, is proposed by combining the RMS velocity method and SAFT ultrasound imaging. First, a multi-layer sound velocity model (the relationship model between sound propagation time and sound propagation distance) of the HSR ballastless track is established. The sound propagation time is expressed as a function of the RMS of sound propagation speed as an independent variable. Second, the propagation time of the sound wave in the HSR ballastless track is calculated in accordance with the multi-layer sound velocity model and the obtained propagation time is substituted into the SAFT ultrasound imaging method for imaging. Lastly, the accuracy of the method is verified through a finite element simulation and an experiment. The results show that for the HSR ballastless track with minimal differences in the sound propagation speed at each layer, the sound propagation time calculated by the multi-layer sound wave model has high accuracy. The proposed RMS-SAFT ultrasound imaging method improves the accuracy of traditional SAFT imaging and realises accurate imaging of the void defects of HSR ballastless track. [ABSTRACT FROM AUTHOR]

The degradation of rock masses making up carbonate slopes within water-level fluctuation zones after the impoundment of reservoirs is in some cases very intense. This has attracted widespread concern because such degradation can result in evolving geological hazards. Quantitative characterization of carbonate rock degradation is the key to the study of this phenomenon and its subsequent impacts. In this article, a meter-scale representative observation plane (body) is selected as the research object. The continuous medium mode is used to describe a carbonate rock mass with evenly distributed degradation quantitatively by way of a rock mass degradation variable (De), which is the relative area ratio or volume ratio of new macroscopic defects (bedding planes, joints, cracks, pores, holes, etc.) that form in a representative rock mass within a period of time. For carbonate rock with nonuniform degradation, a further rock mass degradation variable, DeA, is developed, which represents the relative area ratio or volume ratio of the new defects within a discontinuous surface or body within a period of time. Direct and indirect methods and formulae for acquiring these values are presented, dependent upon the degradation process involved, such as mechanical erosion, dissolution, and fissure development or expansion. The De value is established based on the measurement of area, volume, trace length, aperture, eroded depth, and acoustic wave velocity. The resulting formulae are used to analyze the degradation of typical rock masses in the Wu Gorge in the Three Gorges Reservoir area quantitatively. From 2010 to 2013, the De value increased continuously from 0.18 to 0.42 in Maocaopo and showed an accelerating trend. For the Qingshi 6# slope, for the period from 2017 to 2019, the De value showed an overall decreasing trend with increasing depth based on acoustic wave velocity data. The De value of the rock mass underground is greater than 0.2 for eight sections and reaches a maximum of 0.69. The degradation of the rock mass presents structural and zonal characteristics in the depth direction. In Jiandaofeng, the De value is calculated to be 0.0041 for the period from 2012 to 2017, while, at the Sunjiawan cliff, the DeA value of a large structural plane reaches to 1.03 after 10 years of impoundment. This research forms a foundation for the measurement of the degradation of rock masses in the Three Gorges Reservoir area and provides basic technical support for the subsequent study of rock degradation and hazard prevention in the area. Furthermore, it also provides a reference for assessing the degradation of rock masses within the water-level fluctuation zone for other areas around the world. [ABSTRACT FROM AUTHOR]

Copyright of Natural Gas Industry is the property of Natural Gas Industry Journal Agency and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Tunnel Construction / Suidao Jianshe (Zhong-Yingwen Ban) is the property of Tunnel Construction Editorial Office and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Excavation damaged zones (EDZs) in deeply buried underground powerhouse have become major obstacles to design and support, which potentially threaten safety and stability and increase construction and support costs. In this study, investigations of the EDZs were performed by applying an acoustic velocity detecting method in Houziyan hydropower project, southwest of China. A total of 38 testing boreholes distributed in high sidewalls of the main powerhouse were carried out, and corresponding 153 curves were obtained and analyzed. Then, EDZs were divided into highly damaged zone (HDZ), slightly damaged zone (SDZ), and excavation influence zone (EIZ), respectively. Furthermore, we classified the wave velocity curves into four categories: type I, type II, type III, and type IV. EDZs were qualitatively assessed based on the curve categories; in addition, we used a qualitative assessment method, which mainly involved an index of damage degree named D. The assessment results show that HDZ, but not SDZ, was significantly asymmetrically distributed in the upstream (average depth of 4.1 m) and downstream (average depth of 7.5 m) high sidewalls; in partial areas, depth of HDZ exceeded the length of designed rock bolts, which indicates that rock bolts cannot restrain crack development and EDZs evolution. Generally, EDZs distribution was consistent with deformation and failure phenomena distribution; compared to the field failure phenomena, the assessment results were reliable and reasonable. Finally, EDZs formation mechanism was discussed, and it can be concluded that the relatively large intermediate principal stresses σ2 were a critical driving factor of the EDZs evolution. [ABSTRACT FROM AUTHOR]

Due to the heterogeneity of the internal structure and the different external loading conditions, the mechanical and acoustic emission (AE) characteristic parameters of coal and rock are discrete in the process of loading until failure, and many repeated and destructive tests need to be completed to obtain the performance parameters. It is of theoretical significance to explore the correlation of various parameters and to establish multiparameter regression models of coal rock strength and AE characteristics for predicting the strength and acoustic emission characteristic parameters of coal rock and reducing the repeated tests. For the coal sample from a coal seam of Longde Coal Mine in China, the mass density of coal samples and the acoustic velocity in the samples before loading are measured at first, and their respective coefficient of variation is analyzed. Then, the stress-strain curve and the time history curve of AE characteristic parameters are obtained by the uniaxial compression AE test of each coal sample according to the different loading rates. The influence of loading rate, mass density, and acoustic velocity on the mechanical and AE energy parameters of coal sample is analyzed by the section morphology of the coal sample after failure, the three-dimensional location map of AE, and the scanning micrograph of the electron microscope. Based on the least-square method, the multiple regression models of compressive strength, elastic modulus, and the maximum AE energy are established by mass density, acoustic velocity, and loading rate of coal samples. The results indicate that, for the coal samples from the same geological source, the obtained regression models can, respectively, predict the uniaxial compressive strength, elastic modulus, and the maximum AE energy according to the predesigned loading rate, the acoustic velocity, and mass density of coal samples measured before loading, without too many repeated loading failure tests. [ABSTRACT FROM AUTHOR]

Vegetation concrete has been widely applied for the ecological restoration of bare steep slopes in short-term frozen and non-frozen soil regions in China. However, field experiments conducted in seasonally frozen soil regions have revealed decreases in the bulk density, nutrient content and vegetation coverage. This study aimed to clarify the evolution process and mechanism of the engineering properties of vegetation concrete under atmospheric freeze-thaw (F-T) test conditions. The physical, mechanical, and nutrient properties of vegetation concrete were investigated using six F-T cycles (0, 1, 2, 5, 10 and 20) and two initial soil water contents (18 and 22%). The results revealed decreases in the acoustic wave velocity and cohesive forces and an increase in the permeability coefficient of the vegetation concrete owing to F-T action. X-ray diffraction tests indicated that the decreased cohesive force was closely related to the overall decrease in the content of gelling hydration products in the vegetation concrete. Additionally, the contents of NH 4 +–N, PO 4 3–P and K+ in the vegetation concrete increased, whereas that of NO 3 −–N decreased. The loss rates of these soluble nutrients increased, indicating that the nutrient retention capacity of the vegetation concrete had decreased. Specifically, the decreased nutrient retention capacity was mainly related to the disintegration and fragmentation of larger aggregates due to F-T action. This study provides theoretical support for future research on improving the anti-freezing capability of ecological slope protection substrates in seasonally frozen soil regions. [Display omitted] • F-T action reduces acoustic wave velocity and cohesive force, increasing permeability coefficient. • XRD tests indicated decrease in cohesive force closely related to an overall decrease in gelling hydration products. • F-T action reduces nutrient retention capacity of vegetation concrete by disintegrating and fragmenting larger soil aggregates. • Theoretical support for improving anti-freezing capability of ecological slope protection substrates. [ABSTRACT FROM AUTHOR]

To examine the association between daily steps and step intensity with bone health in Chinese community-dwelling older women. Data from 1116 women in the Physical Activity and Health in Older Women Study in China, 2021. Three bone parameters: bone quality index (BQI), speed of sound (SOS), and broadband ultrasound attenuation (BUA) were measured in the left heel using an ultrasound bone densitometer and transformed into dichotomous variables from medians. Daily steps and step intensity (slow step time, brisk step time, peak 1-min cadence, peak 30-min cadence, and peak 60-min cadence) were measured using a triaxial accelerometer. Participants with high BQI, SOS, and BUA levels were used as references for logistic regression models to explore the association of daily steps and step intensity with bone health. Daily steps were positively associated with the BQI (odds ratio [OR] = 0.94, confidence interval [CI] = 0.89,1.00), SOS (OR = 0.93, CI = 0.88,0.99), and BUA (OR = 0.93, CI = 0.88,0.99) among older women. There was no significant association between peak cadence and bone health. Slow step time was positively associated with the BQI (OR = 0.94, CI = 0.90,0.99) and SOS (OR = 0.93, CI = 0.88,0.97), while brisk step time was positively associated with the BQI (OR = 0.89, CI = 0.82,0.97), SOS (OR = 0.87, CI = 0.80,0.94), and BUA (OR = 0.89, CI = 0.82,0.97). Moreover, 10,000 steps/day or more was significantly associated with the BQI (OR = 0.52, CI = 0.33,0.81), SOS (OR = 0.55, CI = 0.35,0.86), and BUA (OR = 0.45, CI = 0.28, 0.70) compared to <6000 steps/day. Increasing the number of daily steps or the duration of walking, whether fast or slow, may benefit the bone health of older women. • Daily steps are an independent protective factor for bone health in older women. • The association between peak cadence and bone health disappeared after controlling for daily steps. • Walking at any intensity for a cumulative period of time (or number of steps) is good for bone health. • Older women with 10,000 or more steps per day have healthier bones than older women with fewer than 6000 steps/day. [ABSTRACT FROM AUTHOR]

A new, high-efficiency technology for fracturing and breaking rocks is required. Due to various advantages including high efficiency, energy-saving, and having no secondary pollution, the technology of microwave-induced fracturing of hard rock has been considered as a potential method for rock fracturing and breaking. Aiming at the realisation of two engineering applications: microwave-assisted mechanical rock breaking and stress release from rock masses in deep underground engineering works to prevent geological disasters caused by high-stress concentrations such as rockbursts, a novel (open-type) microwave-induced fracturing apparatus (OMWFA) for fracturing hard rocks was developed. On this basis, the two modes of microwave-induced subsurface fracturing and microwave-induced borehole fracturing of hard rocks were proposed. Due to removal of the restraint of the microwave cavity, OMWFA can be used to fracture large-size rock samples and engineering-scale rock masses. Using the apparatus, the fracturing effects of the two fracturing modes on different dimensions of cuboidal basalt samples were investigated. By combining the microwave-induced fracturing apparatus with a press machine to explore the influence of unidirectional stress on the fracturing effect of microwave treatment on basalt. Moreover, field tests were carried out on rock masses encountered in underground engineering works at Baihetan Hydropower Station in Sichuan Province, China, and the fracturing effects were evaluated by applying a digital borehole televiewer and conducting acoustic wave testing. The results show that the apparatus had favourable fracturing effects on the subsurface and borehole samples of basalt. When no stress was applied, the cracks radially expanded from the approximate centre of the radiant surface and unidirectional stress promoted fracturing. The number and depth of cracks increased with prolonged microwave exposure. After microwave treatment, the P-wave velocity of the samples declined, and the longer the microwave exposure, the more significant the reduction in P-wave velocity was. The results of field test reveal that borehole fracturing can exhibit a favourable effect around boreholes. The sound velocity around the borehole and between the boreholes both declined to some extent. Microwave-induced hard rock fracturing offers guiding significance to those exploring and developing new rock breaking and tunnelling methods, and generally enhances construction safety in deep underground engineering works. [ABSTRACT FROM AUTHOR]

• We used an automatic detection method to locate and track a warm mesoscale eddy from satellite data. • We deployed hydrophone and temperature-sensor arrays in the center and outside the eddy. • We recorded acoustic signals from explosive sources and chirped signals from a transceiver. • We combined the measured hydrological data to create a spatially and temporally dependent empirical model of the eddy. • We compared the simulations with and without an eddy to investigate the effects of the eddy on sound propagation. • We utilized the measured data to analyze the effects of the eddy on transmission losses to the two hydrographic arrays. • We employed recordings of the chirped signals to study the effects of the eddy on sound-energy fluctuations. The spatial and temporal redistribution of sound energy caused by a warm eddy was measured via a multiday experiment conducted in the South China Sea, utilizing two vertical line arrays, a mooring source, and some wide-band explosive sources. In the experiment area, a warm eddy was identified and tracked using an automatic detection method combined with the empirically reconstructed data. During the experimental period, the warm eddy diminished in size and kinetic energy until it vanished. The influence of the warm eddy on sound propagation during its lifespan is comprehensively analyzed and explained. The experimental acoustic results and simulations based on dynamic hydrographic data demonstrate that energy is redistributed both spatially and temporally due to the presence of the warm eddy. In comparison to the environment without an eddy, the first convergence zone disappears and the high-energy region appears in the typical position of the first shadow zone. The oscillating disturbance in energy is mainly affected by the fluctuation of sound speed caused by the warm eddy. [ABSTRACT FROM AUTHOR]

• The existing modified Fourier transform for source depth estimation is ameliorated by an elaborately-designed resampling scheme to achieve a higher estimation accuracy. • The proposed method (compared to the original counterpart) can reduce the estimation bias by about 12%. • The superiority of the method is verified through the experimental data collected in the South Sea of China. The interference characteristics between the direct and surface-reflected paths in deep-water reliable acoustic path (RAP) environment contain the information of source depth. For the narrowband case, the source depth can be estimated by applying a modified Fourier transform to the beam intensity series in the sine domain of the receiving angle, which was first published by McCargar and Zurk [(2013), J. Acoust. Soc. Am. 133(4), EL320-EL325]. However, in practical RAP environment, the imperfect periodicity of the beam intensity series as well as the inappropriate reference sound speed often degrades the accuracy of this method. To address this problem, this paper designs a pre-processing resampling scheme to modulate the beam intensity series. Given a minor amount of priori environmental information, the proposed resampling function including a specified reference sound speed can effectively enhance the periodicity of the beam intensity series, thereby enables the modified Fourier transform to achieve higher accuracy. The effectiveness and superiority of the proposed method are experimentally demonstrated with the data collected in the South Sea of China. The results show that the proposed resampling scheme can reduce the depth estimation bias by about 12%. [ABSTRACT FROM AUTHOR]

Due to extraordinary natural geographical features, seabed topography, and sediment sources, wave-induced silt liquefaction is a common occurrence in the subaqueous delta of the Yellow River, China. When liquefaction occurs, the original sedimentary structure of silt is destroyed; after liquefaction, the sediment particles are rearranged and reconsolidated, resulting in distinct physical and mechanical differences between the liquefied material and the nearby adjacent strata that have not been subjected to liquefaction. Based on data from geotechnical testing (GT), scanning electron microscope (SEM) images, and sub-bottom profiling (SBP), the physical and acoustical characteristics of silt remoulded by wave-induced liquefaction (SRL) in the Yellow River subaqueous delta are determined. According to the GT results, liquefaction resulted in distinct decreases in the water content (2.6%), the void ratio (0.056), and the clay content (4.52%), as well as slight increases in the wet density (0.01 g/cm3), the dry density (0.05 g/cm3), and the grain size (d 50) (0.015 mm). Per our SEM analyses, the SRL material is denser than the unremoulded silt, attributed to the rearrangement and reconsolidation of the silt particles. As can be determined from the high-resolution SBP data, that acoustically, the SRL is distinctly different from the adjacent intact strata. The smooth funnel-shaped features demarcate the extent of the region that has been subjected to a specific liquefaction and silt reconsolidation event. Due to the presence of a fault-like uplifted reflection event in the underlying strata, the SRL produces positive sound velocity anomalies on the order of 53–127 m/s. Analyses of the physical and acoustical characteristics of the SRL provides valuable insight into the engineering properties of seabed silt. • Focusing on physical and acoustic properties of silt after being remoulded by wave-induced liquefaction. • Both the physical features from borehole and SEM images and the acoustical features from high-resolution SBP prove that the liquefaction and remoulding process significantly improves the engineering properties of the seabed silt. • The positive sound velocity anomalies are estimated to have magnitude of 53–127 m/s. [ABSTRACT FROM AUTHOR]

Acoustic velocity is an important parameter to evaluate the mechanical properties of fractured rock masses. Based on the in situ acoustic velocity measurement data of ~20 hydropower stations in China, we assessed the acoustic velocity increase of rock masses as a result of consolidation grouting in different geological conditions, such as fault sites, weathered areas and excavation-induced damage zones. We established an empirical relationship between the acoustic velocity of rock masses before and after consolidation grouting, and examined the correlation between acoustic velocity and deformation modulus. A case study is presented about a foundation consolidation grouting project for an intake tower of Pubugou Hydropower Station. The results show that different types of rock masses possess distinct ranges for resultant acoustic velocity increase by consolidation grouting. Under a confidence interval of 95 %, the ranges of the increasing rate of acoustic velocity in a faulted zone, weathered zone, and excavation-induced damage zone are observed to be 12.7-43.1, 12.3-31.2, and 6.9-14.5 %, respectively. The acoustic velocity before grouting and its increasing rate can be used to predict the effectiveness of consolidation grouting. [ABSTRACT FROM AUTHOR]

Diet quality during reproduction is crucial to maternal and infant health. However, the association between dietary diversity and bone health of pregnant women remains unclear. We aimed to evaluate the dietary quality of Chinese urban gravidas using the dietary diversity score (DDS), and to explore the relationship of the DDS with micronutrient adequacy and bone health. In this cross-sectional study, we analyzed data from 775 pregnant women aged 18 years or older in urban China. Dietary diversity was assessed using the Minimum Dietary Diversity for Women (MDD-W) indicator. A 24-h dietary recall was used to collect diet data and to calculate the MDD-W and the nutrient intake. Bone health was measured using quantitative ultrasound and assessed by the speed of sound (SOS). Pearson's correlation coefficients between the DDS and the nutrient adequacy ratio (NAR) were calculated. A multivariable linear regression model was used to estimate the effect size of the DDS on the SOS. The mean DDS was 6.61 ± 1.53 points and 91.0% of participants reported the consumption of five or more food groups. Women in the diverse diet subgroup (DDS ≥ 7 points) were more likely to consume all kinds of food except starchy staples and had higher NARs. Pearson's correlation coefficients between the DDS and the NAR ranged from 0.161 to 0.484. For participants in the second trimester, those with a diverse diet had a higher SOS. A multivariable linear regression analysis showed that the DDS was positively and significantly associated with the SOS (β = 17.18, 95% CI = 5.97-28.39, p = 0.003), but this was not the case for women in the first and third trimesters. Urban Chinese women had good dietary diversity during pregnancy. A higher dietary diversity was associated with a higher NAR. From the point of view of bone, a diverse diet was positively correlated with better bone status, suggesting the importance of improving diet diversity for pregnant women, especially from mid-pregnancy.

• Source depths are estimated based on the smooth-averaged cross-correlation function. • The proposed methods can provide more accurate source depth estimates than the MFP. • The simulations show the applicable conditions of the proposed methods. A solution to the problem of acoustic source depth estimation in shallow water is presented for the case of two horizontally separated hydrophones or arrays. The solution is based on that the smooth-averaged cross-correlation function (SCF) of signals changes regularly with the source depth and is approximately independent of the source range, allowing that the source depth can be estimated independently without knowing the source range. Using different cost functions, three methods are proposed to estimate source depth by matching the normalized cross-spectral density, temporal envelope and time delay of the SCF. Then, the performance of the proposed methods are evaluated with simulations and two experiments conducted off the coast of China at water depths not exceeding 100 m. The mean absolute errors in source depth of the proposed methods are in 2.8–12.8 m. Finally, the effect of noise, frequency band, range span, horizontal spacing, sound speed profile, and parameter mismatch are numerically studied. The results show that the methods are more suitable for the case of a low-frequency band and an environment with large negative sound speed gradient. [ABSTRACT FROM AUTHOR]

An inversion scheme based on time-warping is presented for estimating seabed sound attenuation from modal dispersion of close-range single-hydrophone data. The dispersion information is extracted directly from the warped signal spectrum. Seabed sound speed and density are inverted from the modal group velocity curves, and the attenuation is inverted from the normalized modal amplitudes. The method is applied to experimental data collected in the Yellow Sea of China during the winter of 2002. The inverted sound speed and density are consistent with the sand-silt-clay sediment at the site, and the attenuation is nonlinear over the frequency band from 125-500 Hz. [ABSTRACT FROM AUTHOR]

A joint China-U.S. underwater acoustics experiment was conducted in the Yellow Sea with a very flat bottom and a strong and sharp thermocline. Broadband explosive sources were deployed both above and below the thermocline along two radial lines up to 57.2 km and a quarter circle with a radius of 34 km. Two inversion schemes are used to obtain the seabottom sound speed. One is based on extracting normal mode depth functions from the cross-spectral density matrix. The other is based on the best match between the calculated and measured modal arrival times for different frequencies. The inverted seabottom sound speed is used as a constraint condition to extract the seabottom sound attenuation by three methods. The first method involves measuring the attenuation coefficients of normal modes. In the second method, the seabottom sound attenuation is estimated by minimizing the difference between the theoretical and measured modal amplitude ratios. The third method is based on finding the best match between the measured and modeled transmission losses (TLs). The resultant seabottom attenuation, averaged over three independent methods, can be expressed as α=(0.33±0.02)f1.86±0.04(dB/m kHz) over a frequency range of 80–1000 Hz. [ABSTRACT FROM AUTHOR]

Based on the 3-D Earth model, the common convert points-phase weighted stacks (CCP-PWS) migration method is used to image the upper mantle discontinuities beneath Northeast China (longitude 120°-132°; latitude 38°-40°) with 802 observed receiver functions. Teleseismic records are obtained from 4 stations belonging to CCDSN and 19 stations belonging to PASSCAL. A low-velocity layer has been detected at the depth of 620 km. This low-velocity layer rises to 600 km in the east of the study region close to the subducted slab. We consider that this low-velocity layer might be the accumulated oceanic crustal material delaminated from the western Pacific subducted slab. Additionally, we detect the obvious depression of 660 km discontinuity which was attributed to the interaction between the upper mantle and subducted slab. The maximum depth of 660 km discontinuity approaches 700 km, and 660 km discontinuity splits into multiple discontinuities in the northeast of the study region. [ABSTRACT FROM AUTHOR]

The physical properties of basic minerals such as magnesium silicates, oxides, and silica at extreme conditions, up to 1000 s of GPa, are crucial to understand the behaviors of magma oceans and melting in Super-Earths discovered to data. Their sound velocity at the conditions relevant to the Super-Earth's mantle is a key parameter for melting process in determining the physical and chemical evolution of planetary interiors. In this article, we used laser indirectly driven shock compression for quartz to document the sound velocity of quartz at pressures of 270 GPa to 870 GPa during lateral unloadings in a high-power laser facility in China. These measurements demonstrate and improve the technique proposed by Li et al. [PRL 120, 215703 (2018)] to determine the sound velocity. The results compare favorably to the SESAME EoS table and previous data. The Grüneisen parameter at extreme conditions was also calculated from sound velocity data. The data presented in our experiment also provide new information on sound velocity to support the dissociation and metallization for liquid quartz at extreme conditions. [ABSTRACT FROM AUTHOR]

We evaluate reference data to examine whether there are sex-, age-, height-, weight- and BMI-related differences of quantitative ultrasound parameters (QUS) for healthy Chinese children and adolescents. A total of 726 healthy children and adolescents (360 male and 366 female) aged from 10–21 years were examined with a Lunar Achilles Express densitometer. The measurements on the right heel included speed of sound (SOS), broadband ultrasound attenuation (BUA), and a calculated stiffness index (SI). Our results found that there were no significant differences for BUA, SOS and SI between males and females, except in the age range of 12 to 13 years. The values of all parameters were significantly higher in the 12-year-old females compared to males, and BUA values were significantly higher in 13-year-old females compared to males. A spurt in QUS parameters were observed at 12 years in females and at 14 years in males. A steady increase of BUA, SOS, and SI was seen with increasing body height and weight in both sexes. In conclusion, the present results can be used as reference data for children and adolescents in China. [ABSTRACT FROM AUTHOR]

Wideband reverberation measurements were made at a fixed location in the East China Sea on 3 and 5 June 2001 using the same measurement system. Sound-speed profiles were similar during both measurements. Wind speed (W) and rms surface-wave height (σ) changed from 2.74 m/s and 0.10 m on 3 June to 7.45 m/s and 0.33 m on 5 June. Thus, these measurements offer an opportunity to evaluate sea-surface effects on reverberation vertical coherence (RVC), RVC-inverted bottom acoustic parameters, and reverberation level (RL) in shallow water. The two sets of RVC and RL data, in a frequency range of 100–2500 Hz, show differences that are the apparent effects of the surface roughness. With increasing sea state, the RVC increases and the RL decreases. The effective bottom losses, inverted from the RVC data, correspond to the variation of sea state. This additional loss gives a physical explanation of the characteristics of both the measured RVC and RL. These preliminary findings show the importance of surface effects in shallow-water reverberation and propagation models. These effects would be pronounced for high frequencies and sea states. For the conditions reported here, the effects were most apparent for f>500 Hz when W=7.45 m/s. [ABSTRACT FROM AUTHOR]

Accurate inversion of sound velocity in a Holocene stratum and a Quaternary stratum was achieved based on rich high-resolution sub-bottom profiles and boreholes in the Jinzhou Bay, Bohai Sea of China. The average value of the sound velocity is 1540.2 m/s in the Holocene stratum and 1764.7 m/s in the Quaternary stratum. The fitting analysis shows that there is an obvious positive linear correlation between the sound velocity and the burial depth of the stratum, with a gradient of 4.5 s−1. The method involving the solution of over-determined equations was innovatively put forward to explore the sound velocity characteristics of different types of sediments. The eigenvalues of the sound velocities of seven types of sediments and weathered rock in the study area are solved: the sound velocities of mud, muddy sand, muddy silty clay, muddy clay, silty clay, clay, silty sand, and strongly weathered rock are 1513.7 m/s, 1484.3 m/s, 1532.0 m/s, 1511.3 m/s, 1693.9 m/s, 1602.7 m/s, 1599.4 m/s, and 2137.7 m/s, respectively. And statistical analysis shows that the sound velocity of the sediment in the study area has obvious quadratic correlations with the void ratio and compressibility. • Based on sub-bottom profiles and boreholes datasets, this paper develops a method of acoustic inversion of seabed sediment. • Innovatively establishing over-determined equations to solve sound velocities of different types of sediments. • Findings can provide important reference values to the geophysical survey and the development of seabed geoacoustics. [ABSTRACT FROM AUTHOR]

To ensure the effectiveness of fracturing treatment and improve the production reserves of individual wells, it is important to accurately predict the in situ stress distribution to prevent the collapse of horizontal wells. From the perspective of reservoir development, under similar structural environments, microscopic factors, such as reservoir and petrophysical characteristics, are often the key factors that affect reservoir fracturing differences and drilling design in different well areas. Therefore, we need to understand the microscopic factors that affect the distribution of in situ stress. Here, we have determined the three-dimensional distribution of in situ stress in the Ordos Basin of China through the finite element numerical simulation method and revealed the influencing factors. By establishing a reservoir heterogeneity model and a geomechanical heterogeneity model and with the finite element method, the 3D distribution of reservoir physical parameters and in situ stress can be predicted, and the effects of the reservoir physical properties, fluid properties, rock acoustic velocity and mechanical properties on the in situ stress can be determined. The clay content is found to be negatively correlated with the horizontal stress difference (Δ σ) and horizontal principal stress difference coefficient (K h). Rock density, porosity, and permeability have little effect on Δ σ and K h. Fluid properties affect the in situ stress magnitude. If the water saturation is greater than 60%, this parameter has a negative correlation with Δ σ and K h. Poisson's ratio has a weak effect on Δ σ but a significant negative correlation with K h. [ABSTRACT FROM AUTHOR]

Integrated three-dimensional seismic, logging, sediment cores, and geochemical testing data were collected from Guangzhou Marine Geological Survey 3 and 4 hydrate drilling expeditions and used in this study for a comprehensive investigation of the geological and geophysical features and accumulation mechanism of hydrates in the first offshore gas-hydrate production test region (GHPTR) in the Shenhu area of the South China Sea. Seismic signatures indicative of disseminated hydrates and free gas include the bottom simulating reflector (BSR), gas chimney, and mud diapir associated with enhanced seismic reflections, acoustic blanking, masking, and chaotic appearance have been observed. The acoustic travel-time responses, density, and compensated neutron three porosity log analysis, high-precision grid tomography inversion analysis, and constrained sparse spike inversion confirm the presence of free gas below the gas-hydrate-bearing zone (GHBZ). Free-gas-bearing zones have significantly different p-wave impedances and low-velocity anomalies than the overlying GHBZ and surrounding strata. These anomalous zones are controlled by the structural attitude of the reservoir strata, which are characterized as inter-bedded stratigraphic units. Variations in the type and geological characteristics of the hydrocarbon migration pathways were observed between sites W18 and W19 on the western ridge and sites W11 and W17 on the eastern ridge in the GMGS study area. The efficiency of gas migration in the western ridge may be higher than that in the eastern ridge, resulting in variations in hydrate gas types, thickness of the GHBZ, and gas migration flux and accumulation. Except for site W11, hydrates were recovered below the structure I inferred BSR at sites W17, W18, and W19. The gas-hydrate stability zone calculations reveal that the structure I hydrate stability zone differs from the BSR depth and is generally shallower than the base of the logging anomaly, indicating the coexistence of structure I and II hydrates. The BSR is not indicative of the BGHSZ; it is rather regarded as a transitional indicator of structure I and II gas hydrates in the GHPTR. The appearance of free gas and hydrates below the structure I inferred BSR indicates that the Shenhu area is characterized by a complex hydrate formation and accumulation system resulting from the supply of biogenic and thermogenic gases. Despite fine-grained host sediments predominating the GHPTR, the coupling of favorable conditions including efficient hydrocarbon generation, sufficient gas supply, multiple pathways for gas migration, and relatively high reservoir porosity have led to the development of highly saturated gas-hydrate accumulations within relatively thick sedimentary sections, which demonstrates a significant resource potential. Image 1 • Gas hydrate petroleum system of the China first offshore hydrate production test region is investigated. • Gas hydrate and underlying free gas are evaluated based on velocity and acoustic impedance inversion. • The BSR represents a transitional indicator of structure I and structure II gas hydrate. • Presence of foraminifera is not a prerequisite for the emergence of high-saturation hydrates. [ABSTRACT FROM AUTHOR]

In this study, 145 poplar (Populus × euramericana cv.'74/76') seedlings, a common plantation tree species in China, were selected and their ultrasonic velocities were measured at four timepoints during the first growth year. After that, 60 poplar seedlings were randomly selected and cut down to determine their acoustic velocity, using the acoustic resonance method. The effects of influencing factors such as wood green density, microfibril angle, growth days, and root-collar diameter on acoustic speed in seedlings and the relationship between ultrasonic speed and acoustic resonance speed were investigated and analyzed in this work. The number of specimens used for investigating growth days and root-collar diameter was 145 in both cases, while 60 and two specimens were used for investigating wood density and the microfibril angle, respectively. The results of this study showed that the ultrasonic speed of poplar seedlings significantly and linearly increased with growth days, within 209 growing days. The ultrasonic velocity of poplar seedlings has a high and positive correlation with growth days, and the correlation was 0.99. However, no significant relationship was found between the ultrasonic velocity and root-collar diameter of poplar seedlings. Furthermore, a low and negative relationship was found between wood density and ultrasonic speed (R2 = 0.26). However, ultrasonic velocity significantly decreased with increasing microfibril angle (MFA) in two seedlings, and thus MFA may have an impact on ultrasonic speed in poplar seedlings. In addition, ultrasonic velocity was found to have a strong correlation with acoustic resonance velocity (R2 = 0.81) and a good correlation, R2 = 0.75, was also found between the dynamic moduli of elasticity from ultrasonic and acoustic resonance tests. The results of this study indicate that the ultrasonic technique can possibly be used to measure the ultrasound speed of young seedlings, and thus early screen seedlings for their stiffness properties in the future. [ABSTRACT FROM AUTHOR]

In order to study the coupling relationship between large earthquakes and the ionosphere, the techniques of ionosphere data acquisition were refined by the Crustal Movement Observation Network of China (CMONOC) to detect the pre-earthquake ionospheric abnormal and coseismic ionospheric disturbances (CID) of the Mw 6.6 Lushan earthquake on 20 April 2013. Based on the regional ionosphere maps (RIMs) derived from the Global Positioning System (GPS) observations of CMONOC, the ionospheric local effects near the epicenter of the Lushan earthquake one month prior to the shock were analyzed. The results show that the total electron content (TEC) anomalies appeared 12–14 (6–8 April), 19 (1 April), and 25–27 (24–26 March) days prior to the Lushan earthquake, which are defined as periods 1, 2, and 3, respectively. Multi-indices including the ring current index (Dst), geomagnetic planetary (Kp) index, wind plasma speed (Vsw) index, F10.7, and solar flares were utilized to represent the solar–terrestrial environment in different scales and eliminate the effects of solar and geomagnetic activities on the ionosphere. After the interference of solar–terrestrial activity and the diurnal variation in the lower thermosphere were excluded, the TEC variations with obvious equatorial ionospheric anomaly (EIA) in period-1 were considered to be related to the Lushan earthquake. We further retrieved precise slant TECs (STECs) near the epicenter to study the coseismic ionospheric disturbance (CID). The results show that there was clear STEC disturbance occurring within half an hour after the Lushan earthquake, and the CID propagation distance was less than the impact radius of the Lushan earthquake (689 km). The shell models with different altitudes were adopted to analyze the propagation speed of the CID. It is found that at the F2-layer with the altitude of 277 km, which had a CID horizontal propagation velocity of 0.84 ± 0.03 km/s, was in accordance with the acoustic wave propagation velocity. The calculated velocity acoustic wave from the epicenter to the ionospheric pierce points of this shell model was about 0.53 ± 0.03 km/s, which was also consistent with its actual velocity within the altitude of 0–277 km. Affected by the geomagnetic field, the CID mainly propagated along the southeast direction at the azimuth of 190°, which was almost parallel to the local magnetic line. [ABSTRACT FROM AUTHOR]