On September 5,2022,a strong MS6.8 earthquake struck the Luding area in the Kangding-Moxi segment of the Xianshuihe fault zone,which is the northern boundary of the Sichuan-Yunnan rhombic block,causing considerable ca...On September 5,2022,a strong MS6.8 earthquake struck the Luding area in the Kangding-Moxi segment of the Xianshuihe fault zone,which is the northern boundary of the Sichuan-Yunnan rhombic block,causing considerable casualties.The Bamei-Kangding segment of the Xianshuihe fault zone,which is located only tens of kilometers away from the Luding earthquake,has hosted frequent moderate to strong earthquakes in history and is a dangerous earthquake-prone zone.Therefore,it is critical to investigate the regional seismogenic environment for strong earthquakes and to evaluate the impact of the Luding earthquake in this area.For this purpose,we deployed a dense seismic array comprising over 200 short-period nodes in this region from July to August,2022 and acquired seismic ambient noise for over 30 days.Using the collected data,we conducted surface wave tomography and obtained a high-resolution 3-D shear wave velocity model for the regional shallow crust down to 8 km in depth.The key findings include:(1)the Bamei-Kangding segment of the Xianshuihe fault zone exhibits widespread stripped lowvelocity anomalies,suggesting shear movements at a relatively high temperature of the Xianshuihe fault zone;the Zheduoshan granitic pluton situated between the Zheduotang and southern Selaha faults shows a distinct low-velocity anomaly,which may be attributed to the localized high-temperature anomaly resulted by a deep magmatic heat source and the recent rapid uplift of the Zheduoshan area;(2)a ten-kilometer-wide high velocity body found below 4 km in depth near the Zhonggu area in the Bamei segment coincides with the seismic gap of moderate to strong earthquakes in this region,suggesting that the high velocity body may act as a seismic barrier;(3)the heterogeneity of the velocity structure along the Bamei-Kangding segment of the Xianshuihe fault zone corresponds to the regional changes in temperature,which reveals the reason for the spatially varying seismogenic potential in this segment;especially,the Selaha and Zheduotang faults which展开更多
In this study, we conducted ambient noise tomography(ANT), with 33-day data, to investigate the nearsurface shear-velocity structure in downtown Ji’nan, Shandong Province, China. The cross-correlation functions with ...In this study, we conducted ambient noise tomography(ANT), with 33-day data, to investigate the nearsurface shear-velocity structure in downtown Ji’nan, Shandong Province, China. The cross-correlation functions with quiet clear Rayleigh waves are obtained with more symmetrical energy distribution which indicates that strong human activities, such as moving vehicles and municipal engineering construction, can produce approximately isotropic distribution of noise sources for high-frequency signals. The direct surfacewave tomographic method with period-dependent ray-tracing is used to invert all surface-wave dispersion data in the period band 0.2–1.5 s simultaneously for 3D variations of shear-velocity structure. The study result can help us better understand the local geologic structures, evaluate the distribution and geometry of the fracture-karst media, and assess hazards of the concealed active fault and its effect on the springs in the future.展开更多
112 short-period seismographs were set up in the 400 km^2 area of Pingtan Island and its surrounding areas in Fujian.The combined observations of the airgun source and ambient noise source were carried out using a den...112 short-period seismographs were set up in the 400 km^2 area of Pingtan Island and its surrounding areas in Fujian.The combined observations of the airgun source and ambient noise source were carried out using a dense array to receive the 387 airgun signals excited around the island and one month of continuous ambient noise recording.The 1-D P-wave and S-wave shallow velocity model of Pingtan Island is obtained by the inversion of the airgun body wave’s first arrival time data,and the reliability of the velocity model is verified by using the surface wave phase velocity dispersion curve,which can provide initial model for subsequent 3-D imaging.The experimental results show that this experiment is a successful demonstration of local scale green non-destructive detection,which can provide basic data for shallow surface structure research and strong vibration simulation of the Pingtan Island.展开更多
Complex nature of underwater environment poses biggest challenge towards image acquisition and transmission of underwater images.This paper proposes an integrated approach which consists of a non-learning enhancement ...Complex nature of underwater environment poses biggest challenge towards image acquisition and transmission of underwater images.This paper proposes an integrated approach which consists of a non-learning enhancement method with deep Convolutional Neural Networks(CNN)for compression and reconstruction of the image.The proposed method does color and contrast correction for image enhancement.The enhanced images are down-sampled using 9-layer CNN followed by Discrete Wavelet Transform(DWT).The decompression is done by using Inverse DWT.Further,the sub-pixel up-sampled image is de-blurred using a three-layer CNN.Residual Dense CNN(RD-CNN)is used to improve the quality of the reconstructed image after deblurring.The quality of the reconstructed images is measured using Peak Signal to Noise Ratio(PSNR)and Structural Similarity Index Metric(SSIM).The proposed model provides better image enhancement,compression,and reconstruction quality than the existing state-of-the-art methods and Super Resolution CNN(SRCNN)respectively.展开更多
基金supported by the National Key Research and Development Project of China(Grant No.2021YFC3000602)the Special Fund of Key Laboratory of Earthquake Prediction,CEA(Grant No.2021IEF0103).
文摘On September 5,2022,a strong MS6.8 earthquake struck the Luding area in the Kangding-Moxi segment of the Xianshuihe fault zone,which is the northern boundary of the Sichuan-Yunnan rhombic block,causing considerable casualties.The Bamei-Kangding segment of the Xianshuihe fault zone,which is located only tens of kilometers away from the Luding earthquake,has hosted frequent moderate to strong earthquakes in history and is a dangerous earthquake-prone zone.Therefore,it is critical to investigate the regional seismogenic environment for strong earthquakes and to evaluate the impact of the Luding earthquake in this area.For this purpose,we deployed a dense seismic array comprising over 200 short-period nodes in this region from July to August,2022 and acquired seismic ambient noise for over 30 days.Using the collected data,we conducted surface wave tomography and obtained a high-resolution 3-D shear wave velocity model for the regional shallow crust down to 8 km in depth.The key findings include:(1)the Bamei-Kangding segment of the Xianshuihe fault zone exhibits widespread stripped lowvelocity anomalies,suggesting shear movements at a relatively high temperature of the Xianshuihe fault zone;the Zheduoshan granitic pluton situated between the Zheduotang and southern Selaha faults shows a distinct low-velocity anomaly,which may be attributed to the localized high-temperature anomaly resulted by a deep magmatic heat source and the recent rapid uplift of the Zheduoshan area;(2)a ten-kilometer-wide high velocity body found below 4 km in depth near the Zhonggu area in the Bamei segment coincides with the seismic gap of moderate to strong earthquakes in this region,suggesting that the high velocity body may act as a seismic barrier;(3)the heterogeneity of the velocity structure along the Bamei-Kangding segment of the Xianshuihe fault zone corresponds to the regional changes in temperature,which reveals the reason for the spatially varying seismogenic potential in this segment;especially,the Selaha and Zheduotang faults which
基金supported by China Geological Survey's project(Nos.and DD20189132)Basic Scientific Research project from Chinese Academy of Geological Sciences(No.YWF201901-02)The National Key Research and Development Program of China(Nos.2016YFC0600201,2016YFC0600208 and 2016YFC0600209)
文摘In this study, we conducted ambient noise tomography(ANT), with 33-day data, to investigate the nearsurface shear-velocity structure in downtown Ji’nan, Shandong Province, China. The cross-correlation functions with quiet clear Rayleigh waves are obtained with more symmetrical energy distribution which indicates that strong human activities, such as moving vehicles and municipal engineering construction, can produce approximately isotropic distribution of noise sources for high-frequency signals. The direct surfacewave tomographic method with period-dependent ray-tracing is used to invert all surface-wave dispersion data in the period band 0.2–1.5 s simultaneously for 3D variations of shear-velocity structure. The study result can help us better understand the local geologic structures, evaluate the distribution and geometry of the fracture-karst media, and assess hazards of the concealed active fault and its effect on the springs in the future.
基金sponsored by the Key Technologies R&D Program of Fujian Earthquake Agency(G201703)the Seismic Science and Technology Spark Program,CEA(XH19023Y)
文摘112 short-period seismographs were set up in the 400 km^2 area of Pingtan Island and its surrounding areas in Fujian.The combined observations of the airgun source and ambient noise source were carried out using a dense array to receive the 387 airgun signals excited around the island and one month of continuous ambient noise recording.The 1-D P-wave and S-wave shallow velocity model of Pingtan Island is obtained by the inversion of the airgun body wave’s first arrival time data,and the reliability of the velocity model is verified by using the surface wave phase velocity dispersion curve,which can provide initial model for subsequent 3-D imaging.The experimental results show that this experiment is a successful demonstration of local scale green non-destructive detection,which can provide basic data for shallow surface structure research and strong vibration simulation of the Pingtan Island.
文摘Complex nature of underwater environment poses biggest challenge towards image acquisition and transmission of underwater images.This paper proposes an integrated approach which consists of a non-learning enhancement method with deep Convolutional Neural Networks(CNN)for compression and reconstruction of the image.The proposed method does color and contrast correction for image enhancement.The enhanced images are down-sampled using 9-layer CNN followed by Discrete Wavelet Transform(DWT).The decompression is done by using Inverse DWT.Further,the sub-pixel up-sampled image is de-blurred using a three-layer CNN.Residual Dense CNN(RD-CNN)is used to improve the quality of the reconstructed image after deblurring.The quality of the reconstructed images is measured using Peak Signal to Noise Ratio(PSNR)and Structural Similarity Index Metric(SSIM).The proposed model provides better image enhancement,compression,and reconstruction quality than the existing state-of-the-art methods and Super Resolution CNN(SRCNN)respectively.
