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42 Research products, page 1 of 5

  • Canada
  • 2021-2021
  • NEANIAS Underwater Research Community

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  • Closed Access
    Authors: 
    Brian P. V. Hunt; Kerrie M. Swadling;
    Publisher: Elsevier BV

    Abstract The Kerguelen Plateau is the largest topographic barrier to the eastward flowing Antarctic Circumpolar Current (ACC) in the Indian Sector of the Southern Ocean. The plateau is separated into a northern and southern plateau by the Fawn Trough. The northern plateau has a shallow bathymetry (

  • Closed Access
    Authors: 
    Maxime Miron-Morin; David R. Barclay; Jean-Francois Bousquet;
    Publisher: Institute of Electrical and Electronics Engineers (IEEE)
    Project: NSERC

    This article analyzes the effects of key physical oceanographic conditions on underwater propagation in a shallow water environment. Signals at 2 kHz were transmitted and received over ranges of 1–10 km, and the variability in the sound-speed profile, bathymetry, position of the instruments, and sea surface roughness was measured and the uncertainty on each parameter was estimated. The acoustic channel characteristics, including the transmission loss, delay spread, and coherence time, were calculated between a moored five-element vertical line array and a vessel deployed source. The measurement results were modeled using a Bellhop's ray tracing algorithm. The sensitivity of the simulator output was evaluated as a function of the environmental conditions, and the observed variability in the transmission loss was reproduced by varying the input parameters to the model within the observed and estimated bounds. The relative importance of the physical properties of the environment in terms of their impact on the acoustic channel is determined through a comparison of modeled and measured transmission loss variability.

  • Closed Access
    Authors: 
    Cole A. McCormick; Brian Jones;
    Publisher: Elsevier BV
    Project: NSERC

    Abstract Carbonate sedimentary successions that developed on isolated oceanic islands typically comprise a series of unconformity-bounded packages of strata that reflect eustatic sea level changes superimposed on local tectonic movements. Resolving the subsidence and/or uplift of these islands, which are often assumed to have simple tectonic histories, is challenging because the tectonic movements are commonly of similar magnitudes to the eustatic oscillations. The uncertainty associated with each of the components involved in the construction of subsidence diagrams (e.g., age constraints, decompaction, eustatic sea level curves, paleobathymetry), therefore, introduces significant error margins when assessing the tectonic histories of isolated carbonate platforms. By using two end-member subsidence diagrams for the Paleogene to Neogene successions on Grand Cayman and Cayman Brac, it can be shown that their subsidence rates were heterogeneous over time and that the evolution of these islands vary significantly even though they are situated in the same basin. Although these islands, located 150 km apart, were subject to uniform changes in eustatic sea level, they have different stratigraphic architectures owing to their independent tectonic histories. From the Oligocene to the late Pliocene, the tectonic histories of Grand Cayman and Cayman Brac were analogous, and they subsided at a rate of 5.6 to 9.9 m/Myr. From the late Pliocene to ~400 ka, however, northeast Cayman Brac was uplifted by 165 m and tilted with a rotational axis offshore from the southwest end of the island, whereas Grand Cayman was uplifted by ~10 m with no rotational component. The results of this study challenge the assumption that isolated carbonate platforms have simple tectonic histories, while exploring and highlighting the common problems that are encountered with the construction of subsidence diagrams.

  • Open Access
    Authors: 
    Wenxue Xu; Kai Guo; Yanxiong Liu; Ziwen Tian; Qiuhua Tang; Zhipeng Dong; Jie Li;
    Publisher: Elsevier BV

    Abstract Airborne Light Detection And Ranging (LiDAR) Bathymetry (ALB) has an unparalleled advantage in integrated sea-land measurements, especially in the acquisition of topographic data in shallow water areas. Sea surface waves are an important factor affecting the quality of ALB data. This paper presents a method that strictly corrects the sea surface wave-induced refraction error for each seabed laser pulse without any complex modeling of the sea surface. In this method, an adaptive neighborhood selection method is first used to calculate the normal sea surface at the moment when a laser pulse enters the water, and then a laser pulse refraction error correction model considering sea surface waves is constructed. The distance condition equation, the angle condition equation and the coplanar condition equation are established based on Snell's law and the geometric relationship among the incident laser pulse, the normal vector of the wavy sea surface and the actual refracted ray in order to calculate the coordinates of each laser point at the seabed after refraction error correction. The experimental results show that sea surface waves have a significant impact on the three-dimensional point cloud coordinates of the underwater topography. Even in calm sea conditions, the plane coordinate displacement error of the seabed point caused by the sea surface waves may reach the meter level, and the depth coordinate displacement error can also exceed 0.2 m. The corrected displacement errors of the planimetric coordinates are significantly greater than the corrected displacement errors of the depth coordinates, which can effectively improve the quality of the ALB data.

  • Closed Access
    Authors: 
    Shan Liu; F. Javier Hernández-Molina; Zhen-yu Lei; Débora Duarte; Hui Chen; Ce Wang; Yaping Lei; Haiteng Zhuo; Shuqin Huang; Li Zhang; +1 more
    Publisher: Elsevier BV

    Abstract Over the past decades, contourite drifts have been widely identified in the deep ocean with their classification constantly being improved. Some contourite drift types, however, are not yet well constrained. The present study investigates contourite drifts in the southern South China Sea for the first time based on high-resolution reflection seismic profiles and bathymetric data, thereby determining the common occurrence of a lesser-known type: the “fault-controlled drift.” In this area, normal fault movements have been active during the Quaternary, associated with the formation of sea-floor irregularities and highs that represented obstacles to Deep Water circulation. Six fault-controlled drifts are generated in the study area due to interactions between regional faulting/fault-generated topography and bottom currents. They are divided into two major types depending on their shapes, locations, and relative faulting movements: Type-1) drifts deposited coeval to the fault movement and are situated over the footwall block top or along the fault scarp, and Type-2) drifts deposited after the fault movement and are located along the fault scarp base. Spatial distribution of these drifts is a result of variations on bottom currents dynamics associated with the South China Sea Deep Water. The South China Sea Deep Water settling depth, 200–300 m shallower than that of the northern South China Sea, tentatively indicates upwelling which may have, in turn, contributed to the South China Sea meridional overturning circulation. The present study demonstrates new types of contourite drifts that are not well-constrained in the literature and require more detailed studies. The types of fault-controlled drift are described based on the relative movement of normal faults. However, future research should be conducted in other active tectonic settings for evaluating fault effects on the sedimentary stacking patterns, geometries, and evolution of contourite drifts.

  • Closed Access
    Authors: 
    Zhengren Zhu; Cui Xiaodong; Kai Zhang; Bo Ai; Bo Shi; Fanlin Yang;
    Publisher: Elsevier BV

    Abstract Seabed sediment classification has significance for the utilization of marine resources and marine scientific research. Currently, the multibeam echo sounder (MBES) is increasingly becoming the tool of choice for large-scale seabed sediment classification. To further explore the technology of seabed sediment classification, this paper proposes a new classification method. In addition to backscatter mosaic, the method also integrates three other different types of features, including texture features of backscatter mosaic, MBES bathymetry features, and backscatter angular response (AR) features, which are given different weights in the classification process. First, geographically weighted regression (GWR) analysis is performed between different types of features and seabed sediment types, and the normalized coefficient of determination (R2) is employed as the weight coefficient for the different types of features. Second, the backscatter mosaic is combined with features from different types to predict the seabed sediment types using a deep neural network (DNN) classifier. Third, the classification residuals of the features from these three different types are acquired through the above classification results. Last, the classification residuals of features from different types are added to the classification results of the backscatter mosaic according to the weights, thereby achieving seabed sediment classification based on MBES multifeatures with different weights. The results show that the overall classification accuracy of the seabed sediments can be significantly improved from 88.98%/85.14% to 93.43% when using the DNN classification model based on MBES multifeatures with different weights compared with the other two models (DNN classification model based on MBES multifeatures with equal weights and DNN classification model based on principal component analysis (PCA) dimensionality reduction). The kappa coefficient can also be significantly improved from approximately 0.85/0.80 to 0.91. Via analysis, the proposed method can reasonably assign the weights of the different features and take advantage of integrating MBES multifeatures for seabed sediment classification. This approach also provides an important reference for future research on seabed sediment classification.

  • Closed Access
    Authors: 
    Cedric Gervaise; Yvan Simard; Florian Aulanier; Nathalie Roy;
    Publisher: Elsevier BV

    Abstract This study addresses the problem of determining optimal design of passive acoustic monitoring (PAM) systems for detecting and localizing whale calls in real-time in variable-noise environments. The performance of various PAM system is assessed using the detection theory and simulation modeling applied to the context of North Atlantic right whale (NARW) upcalls in feeding grounds and noisy shipping corridor of the Gulf of St. Lawrence. Realistic simulations are performed using an estimated NARW upcall source level (SL), the actual shipping traffic, measured local fleet ship SLs, and transmission loss (TL) from a regional 2.5-D propagation model accounting for the bathymetric and environmental structures. The comparisons consider single-hydrophone and hydrophone-array PAM systems, mounted on buoys, gliders, or cabled to shore and three families of NARW upcall detectors. The targeted performance is a low false-alarm rate of 1 per day and a detection probability > 0.5. The time-frequency-based detector offers the best trade-off between detection performance and robustness against NARW upcall variability. The effective detection ranges are ∼ 15 times lower with single-hydrophone systems compared to hydrophone-arrays, whose beamforming enhances the signal in the upcall direction while damping interfering discrete noise from nearby transiting ships in other directions. Detecting and localizing NARWs in the large target areas (>10000-km2 scale) is possible with a few well-located arrays of 10–20 hydrophones, which appears as the optimal cost/performance trade-off.

  • Authors: 
    An-Na Chen; Yi Ma; Jing-Yu Zhang;
    Publisher: Informa UK Limited

    Satellite imagery with high spatial and temporal resolutions provides strong support for remote sensing bathymetry. Heterogeneous underwater environments such as complex bottom types represent the ...

  • Open Access English
    Authors: 
    Benjamin Misiuk; Myriam Lacharité; Craig J. Brown;
    Publisher: Elsevier

    Legacy seabed mapping datasets are increasingly common as the need for detailed seabed information is recognized. Acoustic backscatter data from multibeam echosounders can be a useful surrogate for seabed properties and are commonly used for benthic habitat mapping. Legacy backscatter data, however, are often uncalibrated, rendering measurements relative to a given survey and complicating the use of multisource acoustic datasets for habitat mapping. Recently, ‘bulk shift’ methods have been proposed to harmonize multisource backscatter layers that overlap spatially, but their application to benthic habitat mapping has not been evaluated. Here, four relative backscatter datasets at the St. Anns Bank Marine Protected Area were harmonized to produce a single continuous surface spanning the extent of available bathymetric data. The harmonized surface was used as a predictor in a benthic habitat (‘benthoscape’) classification, which was compared to previous results using individual backscatter coverages. Results were similar to those obtained previously, but the harmonized surface provided increased class discrimination, fewer unclassified areas, and predictions that cross dataset boundaries – eliminating the need for manual reclassification by the user. While this generally increases the efficiency and repeatability of the analysis and the useability of the data, we caution that an inappropriate harmonization model is a potential source of error for the classification.

  • Closed Access
    Authors: 
    Yaochen Xu; Ninghua Chen; Tao Chunhui; Jianyu Chen; Bowen Gao;
    Publisher: Elsevier BV

    Abstract Southwest Indian Ridge (SWIR) is a typical ultra-slow spreading ridge which has been extensively studied based on geophysical survey, geochemical sampling and morphological feature extraction. In this paper, based on the high-resolution multibeam bathymetric data, we extract seven types of topography, including fault, axial rift, axial volcanic ridge (AVR), axial trough, AVR's remnant, volcanic cone and oceanic core complex (OCC). We perform quantitative morphotectonic statistic, verifying the relations between the topography and magmato-tectonic mechanism of SWIR 49–50°E. The analyzed results of flank topography show that the average seafloor depth of the southern flank is shallower than that of the northern flank. The Total Cumulative Length of the faults in the northern and southern flank is 624.6 km and 948.2 km. The number, Total density, Average Length and Maximum Length of the faults in the southern flank are higher than those in the northern flank. An OCC and detachment faults locate in the southern flank. The asymmetry in flank topography indicates the asymmetric spreading mode of the study area. The analyzed results of the axial topography show that AVRs and troughs develop in the rift. The rift is narrower and shallower in the AVR regions, and wider and deeper in the trough regions. These observations support the partition of magmatic and less-magmatic stretching in the study area, and indicate the relation between the variation of rift's depth-width and the magmato-tectonic accretion.

search
Include:
The following results are related to Canada. Are you interested to view more results? Visit OpenAIRE - Explore.
42 Research products, page 1 of 5
  • Closed Access
    Authors: 
    Brian P. V. Hunt; Kerrie M. Swadling;
    Publisher: Elsevier BV

    Abstract The Kerguelen Plateau is the largest topographic barrier to the eastward flowing Antarctic Circumpolar Current (ACC) in the Indian Sector of the Southern Ocean. The plateau is separated into a northern and southern plateau by the Fawn Trough. The northern plateau has a shallow bathymetry (

  • Closed Access
    Authors: 
    Maxime Miron-Morin; David R. Barclay; Jean-Francois Bousquet;
    Publisher: Institute of Electrical and Electronics Engineers (IEEE)
    Project: NSERC

    This article analyzes the effects of key physical oceanographic conditions on underwater propagation in a shallow water environment. Signals at 2 kHz were transmitted and received over ranges of 1–10 km, and the variability in the sound-speed profile, bathymetry, position of the instruments, and sea surface roughness was measured and the uncertainty on each parameter was estimated. The acoustic channel characteristics, including the transmission loss, delay spread, and coherence time, were calculated between a moored five-element vertical line array and a vessel deployed source. The measurement results were modeled using a Bellhop's ray tracing algorithm. The sensitivity of the simulator output was evaluated as a function of the environmental conditions, and the observed variability in the transmission loss was reproduced by varying the input parameters to the model within the observed and estimated bounds. The relative importance of the physical properties of the environment in terms of their impact on the acoustic channel is determined through a comparison of modeled and measured transmission loss variability.

  • Closed Access
    Authors: 
    Cole A. McCormick; Brian Jones;
    Publisher: Elsevier BV
    Project: NSERC

    Abstract Carbonate sedimentary successions that developed on isolated oceanic islands typically comprise a series of unconformity-bounded packages of strata that reflect eustatic sea level changes superimposed on local tectonic movements. Resolving the subsidence and/or uplift of these islands, which are often assumed to have simple tectonic histories, is challenging because the tectonic movements are commonly of similar magnitudes to the eustatic oscillations. The uncertainty associated with each of the components involved in the construction of subsidence diagrams (e.g., age constraints, decompaction, eustatic sea level curves, paleobathymetry), therefore, introduces significant error margins when assessing the tectonic histories of isolated carbonate platforms. By using two end-member subsidence diagrams for the Paleogene to Neogene successions on Grand Cayman and Cayman Brac, it can be shown that their subsidence rates were heterogeneous over time and that the evolution of these islands vary significantly even though they are situated in the same basin. Although these islands, located 150 km apart, were subject to uniform changes in eustatic sea level, they have different stratigraphic architectures owing to their independent tectonic histories. From the Oligocene to the late Pliocene, the tectonic histories of Grand Cayman and Cayman Brac were analogous, and they subsided at a rate of 5.6 to 9.9 m/Myr. From the late Pliocene to ~400 ka, however, northeast Cayman Brac was uplifted by 165 m and tilted with a rotational axis offshore from the southwest end of the island, whereas Grand Cayman was uplifted by ~10 m with no rotational component. The results of this study challenge the assumption that isolated carbonate platforms have simple tectonic histories, while exploring and highlighting the common problems that are encountered with the construction of subsidence diagrams.

  • Open Access
    Authors: 
    Wenxue Xu; Kai Guo; Yanxiong Liu; Ziwen Tian; Qiuhua Tang; Zhipeng Dong; Jie Li;
    Publisher: Elsevier BV

    Abstract Airborne Light Detection And Ranging (LiDAR) Bathymetry (ALB) has an unparalleled advantage in integrated sea-land measurements, especially in the acquisition of topographic data in shallow water areas. Sea surface waves are an important factor affecting the quality of ALB data. This paper presents a method that strictly corrects the sea surface wave-induced refraction error for each seabed laser pulse without any complex modeling of the sea surface. In this method, an adaptive neighborhood selection method is first used to calculate the normal sea surface at the moment when a laser pulse enters the water, and then a laser pulse refraction error correction model considering sea surface waves is constructed. The distance condition equation, the angle condition equation and the coplanar condition equation are established based on Snell's law and the geometric relationship among the incident laser pulse, the normal vector of the wavy sea surface and the actual refracted ray in order to calculate the coordinates of each laser point at the seabed after refraction error correction. The experimental results show that sea surface waves have a significant impact on the three-dimensional point cloud coordinates of the underwater topography. Even in calm sea conditions, the plane coordinate displacement error of the seabed point caused by the sea surface waves may reach the meter level, and the depth coordinate displacement error can also exceed 0.2 m. The corrected displacement errors of the planimetric coordinates are significantly greater than the corrected displacement errors of the depth coordinates, which can effectively improve the quality of the ALB data.

  • Closed Access
    Authors: 
    Shan Liu; F. Javier Hernández-Molina; Zhen-yu Lei; Débora Duarte; Hui Chen; Ce Wang; Yaping Lei; Haiteng Zhuo; Shuqin Huang; Li Zhang; +1 more
    Publisher: Elsevier BV

    Abstract Over the past decades, contourite drifts have been widely identified in the deep ocean with their classification constantly being improved. Some contourite drift types, however, are not yet well constrained. The present study investigates contourite drifts in the southern South China Sea for the first time based on high-resolution reflection seismic profiles and bathymetric data, thereby determining the common occurrence of a lesser-known type: the “fault-controlled drift.” In this area, normal fault movements have been active during the Quaternary, associated with the formation of sea-floor irregularities and highs that represented obstacles to Deep Water circulation. Six fault-controlled drifts are generated in the study area due to interactions between regional faulting/fault-generated topography and bottom currents. They are divided into two major types depending on their shapes, locations, and relative faulting movements: Type-1) drifts deposited coeval to the fault movement and are situated over the footwall block top or along the fault scarp, and Type-2) drifts deposited after the fault movement and are located along the fault scarp base. Spatial distribution of these drifts is a result of variations on bottom currents dynamics associated with the South China Sea Deep Water. The South China Sea Deep Water settling depth, 200–300 m shallower than that of the northern South China Sea, tentatively indicates upwelling which may have, in turn, contributed to the South China Sea meridional overturning circulation. The present study demonstrates new types of contourite drifts that are not well-constrained in the literature and require more detailed studies. The types of fault-controlled drift are described based on the relative movement of normal faults. However, future research should be conducted in other active tectonic settings for evaluating fault effects on the sedimentary stacking patterns, geometries, and evolution of contourite drifts.

  • Closed Access
    Authors: 
    Zhengren Zhu; Cui Xiaodong; Kai Zhang; Bo Ai; Bo Shi; Fanlin Yang;
    Publisher: Elsevier BV

    Abstract Seabed sediment classification has significance for the utilization of marine resources and marine scientific research. Currently, the multibeam echo sounder (MBES) is increasingly becoming the tool of choice for large-scale seabed sediment classification. To further explore the technology of seabed sediment classification, this paper proposes a new classification method. In addition to backscatter mosaic, the method also integrates three other different types of features, including texture features of backscatter mosaic, MBES bathymetry features, and backscatter angular response (AR) features, which are given different weights in the classification process. First, geographically weighted regression (GWR) analysis is performed between different types of features and seabed sediment types, and the normalized coefficient of determination (R2) is employed as the weight coefficient for the different types of features. Second, the backscatter mosaic is combined with features from different types to predict the seabed sediment types using a deep neural network (DNN) classifier. Third, the classification residuals of the features from these three different types are acquired through the above classification results. Last, the classification residuals of features from different types are added to the classification results of the backscatter mosaic according to the weights, thereby achieving seabed sediment classification based on MBES multifeatures with different weights. The results show that the overall classification accuracy of the seabed sediments can be significantly improved from 88.98%/85.14% to 93.43% when using the DNN classification model based on MBES multifeatures with different weights compared with the other two models (DNN classification model based on MBES multifeatures with equal weights and DNN classification model based on principal component analysis (PCA) dimensionality reduction). The kappa coefficient can also be significantly improved from approximately 0.85/0.80 to 0.91. Via analysis, the proposed method can reasonably assign the weights of the different features and take advantage of integrating MBES multifeatures for seabed sediment classification. This approach also provides an important reference for future research on seabed sediment classification.

  • Closed Access
    Authors: 
    Cedric Gervaise; Yvan Simard; Florian Aulanier; Nathalie Roy;
    Publisher: Elsevier BV

    Abstract This study addresses the problem of determining optimal design of passive acoustic monitoring (PAM) systems for detecting and localizing whale calls in real-time in variable-noise environments. The performance of various PAM system is assessed using the detection theory and simulation modeling applied to the context of North Atlantic right whale (NARW) upcalls in feeding grounds and noisy shipping corridor of the Gulf of St. Lawrence. Realistic simulations are performed using an estimated NARW upcall source level (SL), the actual shipping traffic, measured local fleet ship SLs, and transmission loss (TL) from a regional 2.5-D propagation model accounting for the bathymetric and environmental structures. The comparisons consider single-hydrophone and hydrophone-array PAM systems, mounted on buoys, gliders, or cabled to shore and three families of NARW upcall detectors. The targeted performance is a low false-alarm rate of 1 per day and a detection probability > 0.5. The time-frequency-based detector offers the best trade-off between detection performance and robustness against NARW upcall variability. The effective detection ranges are ∼ 15 times lower with single-hydrophone systems compared to hydrophone-arrays, whose beamforming enhances the signal in the upcall direction while damping interfering discrete noise from nearby transiting ships in other directions. Detecting and localizing NARWs in the large target areas (>10000-km2 scale) is possible with a few well-located arrays of 10–20 hydrophones, which appears as the optimal cost/performance trade-off.

  • Authors: 
    An-Na Chen; Yi Ma; Jing-Yu Zhang;
    Publisher: Informa UK Limited

    Satellite imagery with high spatial and temporal resolutions provides strong support for remote sensing bathymetry. Heterogeneous underwater environments such as complex bottom types represent the ...

  • Open Access English
    Authors: 
    Benjamin Misiuk; Myriam Lacharité; Craig J. Brown;
    Publisher: Elsevier

    Legacy seabed mapping datasets are increasingly common as the need for detailed seabed information is recognized. Acoustic backscatter data from multibeam echosounders can be a useful surrogate for seabed properties and are commonly used for benthic habitat mapping. Legacy backscatter data, however, are often uncalibrated, rendering measurements relative to a given survey and complicating the use of multisource acoustic datasets for habitat mapping. Recently, ‘bulk shift’ methods have been proposed to harmonize multisource backscatter layers that overlap spatially, but their application to benthic habitat mapping has not been evaluated. Here, four relative backscatter datasets at the St. Anns Bank Marine Protected Area were harmonized to produce a single continuous surface spanning the extent of available bathymetric data. The harmonized surface was used as a predictor in a benthic habitat (‘benthoscape’) classification, which was compared to previous results using individual backscatter coverages. Results were similar to those obtained previously, but the harmonized surface provided increased class discrimination, fewer unclassified areas, and predictions that cross dataset boundaries – eliminating the need for manual reclassification by the user. While this generally increases the efficiency and repeatability of the analysis and the useability of the data, we caution that an inappropriate harmonization model is a potential source of error for the classification.

  • Closed Access
    Authors: 
    Yaochen Xu; Ninghua Chen; Tao Chunhui; Jianyu Chen; Bowen Gao;
    Publisher: Elsevier BV

    Abstract Southwest Indian Ridge (SWIR) is a typical ultra-slow spreading ridge which has been extensively studied based on geophysical survey, geochemical sampling and morphological feature extraction. In this paper, based on the high-resolution multibeam bathymetric data, we extract seven types of topography, including fault, axial rift, axial volcanic ridge (AVR), axial trough, AVR's remnant, volcanic cone and oceanic core complex (OCC). We perform quantitative morphotectonic statistic, verifying the relations between the topography and magmato-tectonic mechanism of SWIR 49–50°E. The analyzed results of flank topography show that the average seafloor depth of the southern flank is shallower than that of the northern flank. The Total Cumulative Length of the faults in the northern and southern flank is 624.6 km and 948.2 km. The number, Total density, Average Length and Maximum Length of the faults in the southern flank are higher than those in the northern flank. An OCC and detachment faults locate in the southern flank. The asymmetry in flank topography indicates the asymmetric spreading mode of the study area. The analyzed results of the axial topography show that AVRs and troughs develop in the rift. The rift is narrower and shallower in the AVR regions, and wider and deeper in the trough regions. These observations support the partition of magmatic and less-magmatic stretching in the study area, and indicate the relation between the variation of rift's depth-width and the magmato-tectonic accretion.