Background: Forest canopy height is a key forest structure parameter. Precisely estimating forest canopy height is vital to improve forest management and ecological modelling. Compared with discrete-return LiDAR(Light...Background: Forest canopy height is a key forest structure parameter. Precisely estimating forest canopy height is vital to improve forest management and ecological modelling. Compared with discrete-return LiDAR(Light Detection and Ranging), small-footprint full-waveform airborne LiDAR(FWL) techniques have the capability to acquire precise forest structural information. This research mainly focused on the influence of voxel size on forest canopy height estimates.Methods: A range of voxel sizes(from 10.0 m to 40.0 m interval of 2 m) were tested to obtain estimation accuracies of forest canopy height with different voxel sizes. In this study, all the waveforms within a voxel size were aggregated into a voxel-based LiDAR waveform, and a range of waveform metrics were calculated using the voxelbased LiDAR waveforms. Then, we established estimation model of forest canopy height using the voxel-based waveform metrics through Random Forest(RF) regression method.Results and conclusions: The results showed the voxel-based method could reliably estimate forest canopy height using FWL data. In addition, the voxel sizes had an important influence on the estimation accuracies(R2 ranged from 0.625 to 0.832) of forest canopy height. However, the R2 values did not monotonically increase or decrease with the increase of voxel size in this study. The best estimation accuracy produced when the voxel size was 18 m(R2= 0.832, RMSE = 2.57 m, RMSE% = 20.6%). Compared with the lowest estimation accuracy, the R2 value had a significant improvement(33.1%) when using the optimal voxel size. Finally, through the optimal voxel size, we produced the forest canopy height distribution map for this study area using RF regression model. Our findings demonstrate that the optimal voxel size need to be determined for improving estimation accuracy of forest parameter using small-footprint FWL data.展开更多
Presently, most full-waveform inversion methods are developed for elastic media and ignore the effect of attenuation. The calculation of the quality factor Q is based on velocity parameter inversion under the assumpti...Presently, most full-waveform inversion methods are developed for elastic media and ignore the effect of attenuation. The calculation of the quality factor Q is based on velocity parameter inversion under the assumption of a given Q-model that is obtained by tomographic inversion. However, the resolution of the latter is low and cannot reflect the amplitude attenuation and phase distortion during wave propagation in viscoelastic media. Thus, a Q waveform inversion method is proposed. First, we use standard linear body theory to describe attenuation and then we derive the simplified viscoacoustic equation that characterizes amplitude attenuation and phase distortion. In comparison with conventional equations, the simplifi ed equation involves no memory variables and therefore requires less memory during computation. Moreover, the implementations of the attenuation compensation are easier. The adjoint equation and the corresponding gradient equation with respect to either L2-norm or the zero-lag cross-correlation objective function are then derived and the regularization strategy for overcoming the instability during numerical solution of the adjoint equation is proposed. The Q waveform inversion is developed using the limited-memory Broyden–Fletcher– Goldfarb–Shanno (L-BFGS) iteration method for known velocity. To alleviate the dependence of the waveform inversion on the initial model and overcome cycle skipping to some extent, we adopt multiscale analysis. Furthermore, anti-noise property and double-parameter inversion are assessed based on the results of numerical modeling.展开更多
The main challenge in bone ultrasound imaging is the large acoustic impedance contrast and sound velocity differences between the bone and surrounding soft tissue. It is difficult for conventional pulse-echo modalitie...The main challenge in bone ultrasound imaging is the large acoustic impedance contrast and sound velocity differences between the bone and surrounding soft tissue. It is difficult for conventional pulse-echo modalities to give accurate ultrasound images for irregular bone boundaries and microstructures using uniform sound velocity assumption rather than getting a prior knowledge of sound speed. To overcome these limitations, this paper proposed a frequency-domain fullwaveform inversion(FDFWI) algorithm for bone quantitative imaging utilizing ultrasonic computed tomography(USCT).The forward model was calculated in the frequency domain by solving the full-wave equation. The inverse problem was solved iteratively from low to high discrete frequency components via minimizing a cost function between the modeled and measured data. A quasi-Newton method called the limited-memory Broyden–Fletcher–Goldfarb–Shanno algorithm(L-BFGS) was utilized in the optimization process. Then, bone images were obtained based on the estimation of the velocity and density. The performance of the proposed method was verified by numerical examples, from tubular bone phantom to single distal fibula model, and finally with a distal tibia-fibula pair model. Compared with the high-resolution peripheral quantitative computed tomography(HR-p QCT), the proposed FDFWI can also clearly and accurately presented the wavelength scaled pores and trabeculae in bone images. The results proved that the FDFWI is capable of reconstructing high-resolution ultrasound bone images with sub-millimeter resolution. The parametric bone images may have the potential for the diagnosis of bone disease.展开更多
Full-waveform inversion(FWI)is a powerful tool to reconstruct subsurface geophysical parameters with high resolution.As3 D surveys become widely implemented,corresponding 3 D processing techniques are required to solv...Full-waveform inversion(FWI)is a powerful tool to reconstruct subsurface geophysical parameters with high resolution.As3 D surveys become widely implemented,corresponding 3 D processing techniques are required to solve complex geological cases,while a large amount of computation is the most challenging problem.We propose an adaptive variable-grid 3 D FWI on graphics processing unit devices to improve computational efficiency without losing accuracy.The irregular-grid discretization strategy is based on a dispersion relation,and the grid size adapts to depth,velocity,and frequency automatically.According to the transformed grid coordinates,we derive a modified acoustic wave equation and apply it to full wavefield simulation.The 3 D variable-grid modeling is conducted on several 3 D models to validate its feasibility,accuracy and efficiency.Then we apply the proposed modeling method to full-waveform inversion for source and residual wavefield propagation.It is demonstrated that the adaptive variable-grid FWI is capable of decreasing computing time and memory requirements.From the inversion results of the 3 D SEG/EAGE overthrust model,our method retains inversion accuracy when recovering both thrust and channels.展开更多
Full-waveform velocity inversion based on the acoustic wave equation in the time domain is investigated in this paper. The inversion is the iterative minimization of the misfit between observed data and synthetic data...Full-waveform velocity inversion based on the acoustic wave equation in the time domain is investigated in this paper. The inversion is the iterative minimization of the misfit between observed data and synthetic data obtained by a numerical solution of the wave equation. Two inversion algorithms in combination with the CG method and the BFGS method are described respectively. Numerical computations for two models including the benchmark Marmousi model with complex structure are implemented. The inversion results show that the BFGS-based algorithm behaves better in inversion than the CG-based algorithm does. Moreover, the good inversion result for Marmousi model with the BFGS-based algorithm suggests the quasi-Newton methods can provide an important tool for large-scale velocity inversion. More computations demonstrate the correctness and effectives of our inversion algorithms and code.展开更多
We present the results of using a photon-eounting full-waveform lidar to obtain detailed target information with high accuracy.The parameters of the waveforms(i.e.,vertical structure,peak position,peak amplitude,peak ...We present the results of using a photon-eounting full-waveform lidar to obtain detailed target information with high accuracy.The parameters of the waveforms(i.e.,vertical structure,peak position,peak amplitude,peak width and backscatter cross section)are derived with a high resolution limit of 31 mm to establish the vertical structure and scattering properties of targets,which contribute to the recognition and classification of various scatterers.The photon-counting full-waveform lidar has higher resolution than linear-mode full-waveform lidar,and it can obtain more specific target information compared to photon-counting discrete-point lidar,which can provide a potential alternative technique for tomographic surveying and mapping.展开更多
Tunnel seismic detection methods are effective for obtaining the geological structure around the tunnel face,which is critical for safe construction and disaster mitigation in tunnel engineering.However,there is often...Tunnel seismic detection methods are effective for obtaining the geological structure around the tunnel face,which is critical for safe construction and disaster mitigation in tunnel engineering.However,there is often a lack of accuracy in the acquired geological information and physical properties ahead of the tunnel face in the current tunnel seismic detection methods.Thus,we apply a frequency-domain acoustic full-waveform inversion(FWI)method to obtain high-resolution results for the tunnel structure.We discuss the influence of the frequency group selection strategy and the tunnel observation system settings regarding the inversion results and determine the structural imaging and physical property parameter inversion of abnormal geological bodies ahead of the tunnel face.Based on the conventional strategies of frequency-domain acoustic FWI,we propose a frequency group selection strategy that combines a low-frequency selection covering the vertical wavenumber and a high-frequency selection of antialiasing.This strategy can effectively obtain the spatial structure and physical parameters of the geology ahead of the tunnel face and improve the inversion resolution.In addition,by linearly increasing the side length of the tunnel observation system,we share the influence of the length of the two sides of the observation systems of different tunnels on the inversion results.We found out that the inversion results are the best when the side length is approximately five times the width of the tunnel face,and the influence of increasing the side observation length beyond this range on the inversion results can be ignored.Finally,based on this approach,we invert for the complex multi-stratum model,and an accurate structure and physical property parameters of the complex stratum ahead of the tunnel face are obtained,which verifies the feasibility of the proposed method.展开更多
Full-waveform decomposition is crucial for obtaining accurate satelliteground distance,the accuracy of which is severely affected by noises.However,the traditional filters all depend on filtering parameters.This pape...Full-waveform decomposition is crucial for obtaining accurate satelliteground distance,the accuracy of which is severely affected by noises.However,the traditional filters all depend on filtering parameters.This paper presents a new and adaptive method for denoising based on empirical mode decomposition(EMD)and Hurst analysis(EMD-Hurst).The noisy full-waveforms are first decomposed into their intrinsic mode functions(IMFs),and the Hurst exponent of each IMF is established by the detrended fluctuation analysis.The IMF is regarded as the highfrequency noise and is deleted if its Hurst exponent is≤0.5.Both simulated and real full-waveforms were conducted to validate and evaluate the method by comparing with six other IMF selection methods via metrics like waveform decomposition consistency ratio(CR),average error of decomposition parameters,and ICESat/GLAS waveformparameter product GLAH05.The comparisons show that:(1)under different SNR conditions,EMD-Hurst performs robustly and obtains a higher CR than other EMD based methods;(2)obtains the highest average CR and a relatively lower average error for the echo parameters;and(3)peak numbers and fitting accuracy for GLAH01 are more reasonable and precise than those of GLAH05,which could offer a good reference for the processing on future space-borne full-waveform data.展开更多
Due to the recent system developments for the electromagnetic characterization of the subsurface, fast and easy acquisition is made feasible due to the fast measurement speed, easy coupling with GPS systems, and the a...Due to the recent system developments for the electromagnetic characterization of the subsurface, fast and easy acquisition is made feasible due to the fast measurement speed, easy coupling with GPS systems, and the availability of multi-channel electromagnetic induction(EMI) and ground penetrating radar(GPR) systems. Moreover, the increasing computer power enables the use of accurate forward modeling programs in advanced inversion algorithms where no approximations are used and the full information content of the measured data can be exploited. Here, recent developments of large-scale quantitative EMI inversion and full-waveform GPR inversion are discussed that yield higher resolution of quantitative medium properties compared to conventional approaches. In both cases a detailed forward model is used in the inversion procedure that is based on Maxwell's equations. The multi-channel EMI data that have different sensing depths for the different source-receiver offset are calibrated using a short electrical resistivity tomography(ERT) calibration line which makes it possible to invert for electrical conductivity changes with depth over large areas. The crosshole GPR full-waveform inversion yields significant higher resolution of the permittivity and conductivity images compared to ray-based inversion results.展开更多
Full-waveform inversion is a promising tool to produce accurate and high-resolution subsurface models.Conventional full-waveform inversion requires an accu-rate estimation of the source wavelet,and its computational c...Full-waveform inversion is a promising tool to produce accurate and high-resolution subsurface models.Conventional full-waveform inversion requires an accu-rate estimation of the source wavelet,and its computational cost is high.We develop a novel source-independent full-waveform inversion method using a hybrid time-and frequency-domain scheme to avoid the requirement of source wavelet estimation and to reduce the computational cost.We employ an amplitude-semblance objective function to not only effectively remove the source wavelet effect on full-waveform inver-sion,but also to eliminate the impact of the inconsistency of source wavelets among different shot gathers on full-waveform inversion.To reduce the high computational cost of full-waveform inversion in the time domain,we implement our new algorithm using a hybrid time-and frequency-domain approach.The forward and backward wave propagation operations are conducted in the time domain,while the frequency-domain wavefields are obtained during modeling using the discrete-time Fourier trans-form.The inversion process is conducted in the frequency domain for selected frequen-cies.We verify our method using synthetic seismic data for the Marmousi model.The results demonstrate that our novel source-independent full-waveform inversion pro-duces accurate velocity models even if the source signature is incorrect.In addition,our method can significantly reduce the computational time using the hybrid time-and frequency-domain approach compared to the conventional full-waveform inversion in the time domain.展开更多
基金funded by the Guangxi Natural Science Fund for Innovation Research Team (No. 2019JJF50001)the Natural Science Foundation of Fujian Province,China (No. 2019 J01396)+1 种基金the Special Fund for Guangxi Innovation and Driving Development (Major science and technology projects)(No. 2018AA13005)the Youth Innovation Promotion Association CAS (2019130)。
文摘Background: Forest canopy height is a key forest structure parameter. Precisely estimating forest canopy height is vital to improve forest management and ecological modelling. Compared with discrete-return LiDAR(Light Detection and Ranging), small-footprint full-waveform airborne LiDAR(FWL) techniques have the capability to acquire precise forest structural information. This research mainly focused on the influence of voxel size on forest canopy height estimates.Methods: A range of voxel sizes(from 10.0 m to 40.0 m interval of 2 m) were tested to obtain estimation accuracies of forest canopy height with different voxel sizes. In this study, all the waveforms within a voxel size were aggregated into a voxel-based LiDAR waveform, and a range of waveform metrics were calculated using the voxelbased LiDAR waveforms. Then, we established estimation model of forest canopy height using the voxel-based waveform metrics through Random Forest(RF) regression method.Results and conclusions: The results showed the voxel-based method could reliably estimate forest canopy height using FWL data. In addition, the voxel sizes had an important influence on the estimation accuracies(R2 ranged from 0.625 to 0.832) of forest canopy height. However, the R2 values did not monotonically increase or decrease with the increase of voxel size in this study. The best estimation accuracy produced when the voxel size was 18 m(R2= 0.832, RMSE = 2.57 m, RMSE% = 20.6%). Compared with the lowest estimation accuracy, the R2 value had a significant improvement(33.1%) when using the optimal voxel size. Finally, through the optimal voxel size, we produced the forest canopy height distribution map for this study area using RF regression model. Our findings demonstrate that the optimal voxel size need to be determined for improving estimation accuracy of forest parameter using small-footprint FWL data.
基金supported by the Open Fund of Sinopec Multi-wave Multicomponent Key Laboratory(Grant No.GSYKY-B09-33)
文摘Presently, most full-waveform inversion methods are developed for elastic media and ignore the effect of attenuation. The calculation of the quality factor Q is based on velocity parameter inversion under the assumption of a given Q-model that is obtained by tomographic inversion. However, the resolution of the latter is low and cannot reflect the amplitude attenuation and phase distortion during wave propagation in viscoelastic media. Thus, a Q waveform inversion method is proposed. First, we use standard linear body theory to describe attenuation and then we derive the simplified viscoacoustic equation that characterizes amplitude attenuation and phase distortion. In comparison with conventional equations, the simplifi ed equation involves no memory variables and therefore requires less memory during computation. Moreover, the implementations of the attenuation compensation are easier. The adjoint equation and the corresponding gradient equation with respect to either L2-norm or the zero-lag cross-correlation objective function are then derived and the regularization strategy for overcoming the instability during numerical solution of the adjoint equation is proposed. The Q waveform inversion is developed using the limited-memory Broyden–Fletcher– Goldfarb–Shanno (L-BFGS) iteration method for known velocity. To alleviate the dependence of the waveform inversion on the initial model and overcome cycle skipping to some extent, we adopt multiscale analysis. Furthermore, anti-noise property and double-parameter inversion are assessed based on the results of numerical modeling.
基金Project supported by the National Natural Science Foundation of China(Grant Nos.11827808,11874289,and 11804056)the National Science Fund for Distinguished Young Scholars of China(Grant No.11525416)+3 种基金Shanghai Municipal Science and Technology Major Project,China(Grant No.2017SHZDZX01)Shanghai Talent Development Fund(Grant No.2018112)State Key Laboratory of ASIC and System Project(Grant No.2018MS004)China Postdoctoral Science Foundation(Grant No.2019M661334)。
文摘The main challenge in bone ultrasound imaging is the large acoustic impedance contrast and sound velocity differences between the bone and surrounding soft tissue. It is difficult for conventional pulse-echo modalities to give accurate ultrasound images for irregular bone boundaries and microstructures using uniform sound velocity assumption rather than getting a prior knowledge of sound speed. To overcome these limitations, this paper proposed a frequency-domain fullwaveform inversion(FDFWI) algorithm for bone quantitative imaging utilizing ultrasonic computed tomography(USCT).The forward model was calculated in the frequency domain by solving the full-wave equation. The inverse problem was solved iteratively from low to high discrete frequency components via minimizing a cost function between the modeled and measured data. A quasi-Newton method called the limited-memory Broyden–Fletcher–Goldfarb–Shanno algorithm(L-BFGS) was utilized in the optimization process. Then, bone images were obtained based on the estimation of the velocity and density. The performance of the proposed method was verified by numerical examples, from tubular bone phantom to single distal fibula model, and finally with a distal tibia-fibula pair model. Compared with the high-resolution peripheral quantitative computed tomography(HR-p QCT), the proposed FDFWI can also clearly and accurately presented the wavelength scaled pores and trabeculae in bone images. The results proved that the FDFWI is capable of reconstructing high-resolution ultrasound bone images with sub-millimeter resolution. The parametric bone images may have the potential for the diagnosis of bone disease.
基金the SWPI group in China University of Petroleum(East China)for financial support and discussions
文摘Full-waveform inversion(FWI)is a powerful tool to reconstruct subsurface geophysical parameters with high resolution.As3 D surveys become widely implemented,corresponding 3 D processing techniques are required to solve complex geological cases,while a large amount of computation is the most challenging problem.We propose an adaptive variable-grid 3 D FWI on graphics processing unit devices to improve computational efficiency without losing accuracy.The irregular-grid discretization strategy is based on a dispersion relation,and the grid size adapts to depth,velocity,and frequency automatically.According to the transformed grid coordinates,we derive a modified acoustic wave equation and apply it to full wavefield simulation.The 3 D variable-grid modeling is conducted on several 3 D models to validate its feasibility,accuracy and efficiency.Then we apply the proposed modeling method to full-waveform inversion for source and residual wavefield propagation.It is demonstrated that the adaptive variable-grid FWI is capable of decreasing computing time and memory requirements.From the inversion results of the 3 D SEG/EAGE overthrust model,our method retains inversion accuracy when recovering both thrust and channels.
文摘Full-waveform velocity inversion based on the acoustic wave equation in the time domain is investigated in this paper. The inversion is the iterative minimization of the misfit between observed data and synthetic data obtained by a numerical solution of the wave equation. Two inversion algorithms in combination with the CG method and the BFGS method are described respectively. Numerical computations for two models including the benchmark Marmousi model with complex structure are implemented. The inversion results show that the BFGS-based algorithm behaves better in inversion than the CG-based algorithm does. Moreover, the good inversion result for Marmousi model with the BFGS-based algorithm suggests the quasi-Newton methods can provide an important tool for large-scale velocity inversion. More computations demonstrate the correctness and effectives of our inversion algorithms and code.
基金Supported by the National Natural Science Foundation of China under Grant Nos 11774095,11804099 and 11621404the Shanghai Basic Research Project under Grant No 18JC1412200the Program of Introducing Talents of Discipline to Universities under Grant No B12024
文摘We present the results of using a photon-eounting full-waveform lidar to obtain detailed target information with high accuracy.The parameters of the waveforms(i.e.,vertical structure,peak position,peak amplitude,peak width and backscatter cross section)are derived with a high resolution limit of 31 mm to establish the vertical structure and scattering properties of targets,which contribute to the recognition and classification of various scatterers.The photon-counting full-waveform lidar has higher resolution than linear-mode full-waveform lidar,and it can obtain more specific target information compared to photon-counting discrete-point lidar,which can provide a potential alternative technique for tomographic surveying and mapping.
基金supported by the National Natural Science Foundation of China(41704146)the Fundamental Research Funds for National Universities,China University of Geosciences(Wuhan)(CUGL180816)。
文摘Tunnel seismic detection methods are effective for obtaining the geological structure around the tunnel face,which is critical for safe construction and disaster mitigation in tunnel engineering.However,there is often a lack of accuracy in the acquired geological information and physical properties ahead of the tunnel face in the current tunnel seismic detection methods.Thus,we apply a frequency-domain acoustic full-waveform inversion(FWI)method to obtain high-resolution results for the tunnel structure.We discuss the influence of the frequency group selection strategy and the tunnel observation system settings regarding the inversion results and determine the structural imaging and physical property parameter inversion of abnormal geological bodies ahead of the tunnel face.Based on the conventional strategies of frequency-domain acoustic FWI,we propose a frequency group selection strategy that combines a low-frequency selection covering the vertical wavenumber and a high-frequency selection of antialiasing.This strategy can effectively obtain the spatial structure and physical parameters of the geology ahead of the tunnel face and improve the inversion resolution.In addition,by linearly increasing the side length of the tunnel observation system,we share the influence of the length of the two sides of the observation systems of different tunnels on the inversion results.We found out that the inversion results are the best when the side length is approximately five times the width of the tunnel face,and the influence of increasing the side observation length beyond this range on the inversion results can be ignored.Finally,based on this approach,we invert for the complex multi-stratum model,and an accurate structure and physical property parameters of the complex stratum ahead of the tunnel face are obtained,which verifies the feasibility of the proposed method.
基金the National Natural Science Foundation of China,under[grant numbers 41822106 and 41571407]China High-resolution Earth Observation System,under[grant number 11-Y20A12-9001-17/18]+3 种基金the Science and Technology Innovation Action Plan of Shanghai,under[grant number 18511102100]the Dawn Program of Shanghai Education Commission,China,under[grant number 18SG22]State Key Laboratory of Disaster Reduction in Civil Engineering,under[grant number SLDRCE19-B-35]the Fundamental Research Funds for the Central Universities of China.
文摘Full-waveform decomposition is crucial for obtaining accurate satelliteground distance,the accuracy of which is severely affected by noises.However,the traditional filters all depend on filtering parameters.This paper presents a new and adaptive method for denoising based on empirical mode decomposition(EMD)and Hurst analysis(EMD-Hurst).The noisy full-waveforms are first decomposed into their intrinsic mode functions(IMFs),and the Hurst exponent of each IMF is established by the detrended fluctuation analysis.The IMF is regarded as the highfrequency noise and is deleted if its Hurst exponent is≤0.5.Both simulated and real full-waveforms were conducted to validate and evaluate the method by comparing with six other IMF selection methods via metrics like waveform decomposition consistency ratio(CR),average error of decomposition parameters,and ICESat/GLAS waveformparameter product GLAH05.The comparisons show that:(1)under different SNR conditions,EMD-Hurst performs robustly and obtains a higher CR than other EMD based methods;(2)obtains the highest average CR and a relatively lower average error for the echo parameters;and(3)peak numbers and fitting accuracy for GLAH01 are more reasonable and precise than those of GLAH05,which could offer a good reference for the processing on future space-borne full-waveform data.
文摘Due to the recent system developments for the electromagnetic characterization of the subsurface, fast and easy acquisition is made feasible due to the fast measurement speed, easy coupling with GPS systems, and the availability of multi-channel electromagnetic induction(EMI) and ground penetrating radar(GPR) systems. Moreover, the increasing computer power enables the use of accurate forward modeling programs in advanced inversion algorithms where no approximations are used and the full information content of the measured data can be exploited. Here, recent developments of large-scale quantitative EMI inversion and full-waveform GPR inversion are discussed that yield higher resolution of quantitative medium properties compared to conventional approaches. In both cases a detailed forward model is used in the inversion procedure that is based on Maxwell's equations. The multi-channel EMI data that have different sensing depths for the different source-receiver offset are calibrated using a short electrical resistivity tomography(ERT) calibration line which makes it possible to invert for electrical conductivity changes with depth over large areas. The crosshole GPR full-waveform inversion yields significant higher resolution of the permittivity and conductivity images compared to ray-based inversion results.
基金supported by the U.S.Department of Energy(DOE)through the Los Alamos National Laboratory(LANL),which is operated by Triad National Security,LLC,for the National Nuclear Security Administration(NNSA)of U.S.DOE under Contract No.89233218CNA000001provided by the LANL Institutional Computing Program,which is supported by the U.S.DOE NNSA under Contract No.89233218CNA000001.
文摘Full-waveform inversion is a promising tool to produce accurate and high-resolution subsurface models.Conventional full-waveform inversion requires an accu-rate estimation of the source wavelet,and its computational cost is high.We develop a novel source-independent full-waveform inversion method using a hybrid time-and frequency-domain scheme to avoid the requirement of source wavelet estimation and to reduce the computational cost.We employ an amplitude-semblance objective function to not only effectively remove the source wavelet effect on full-waveform inver-sion,but also to eliminate the impact of the inconsistency of source wavelets among different shot gathers on full-waveform inversion.To reduce the high computational cost of full-waveform inversion in the time domain,we implement our new algorithm using a hybrid time-and frequency-domain approach.The forward and backward wave propagation operations are conducted in the time domain,while the frequency-domain wavefields are obtained during modeling using the discrete-time Fourier trans-form.The inversion process is conducted in the frequency domain for selected frequen-cies.We verify our method using synthetic seismic data for the Marmousi model.The results demonstrate that our novel source-independent full-waveform inversion pro-duces accurate velocity models even if the source signature is incorrect.In addition,our method can significantly reduce the computational time using the hybrid time-and frequency-domain approach compared to the conventional full-waveform inversion in the time domain.