Global Bathymetry and Topography at 15 Arc Sec: SRTM15 Tozer, B.; Sandwell, D. T.; Smith, W. H. F. ...
Earth and space science (Hoboken, N.J.),
October 2019, 2019-10-00, 20191001, 2019-10-01, Letnik:
6, Številka:
10
Journal Article
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An updated global bathymetry and topography grid is presented using a spatial sampling interval of 15 arc sec. The bathymetry is produced using a combination of shipboard soundings and depths ...predicted using satellite altimetry. New data consists of >33.6 million multibeam and singlebeam measurements collated by several institutions, namely, the National Geospatial‐Intelligence Agency, Japan Agency for Marine‐Earth Science and Technology, Geoscience Australia, Center for Coastal and Ocean Mapping, and Scripps Institution of Oceanography. New altimetry data consists of 48, 14, and 12 months of retracked range measurements from Cryosat‐2, SARAL/AltiKa, and Jason‐2, respectively. With respect to SRTM15_PLUS (Olson et al.,), the inclusion of these new data results in a ∼1.4‐km improvement in the minimum wavelength recovered for sea surface free‐air gravity anomalies, a small increase in the accuracy of altimetrically derived predicted depths, and a 1.24% increase, from 9.60% to 10.84%, in the total area of ocean floor that is constrained by shipboard soundings at 15‐arc sec resolution. Bathymetric grid cells constrained by satellite altimetry have estimated uncertainties of ±150 m in the deep oceans and ±180 m between coastlines and the continental rise. Onshore, topography data are sourced from previously published digital elevation models, predominately SRTM‐CGIAR V4.1 between 60°N and 60°S. ArcticDEM is used above 60°N, while Reference Elevation Model of Antarctica is used below 62°S. Auxiliary grids illustrating shipboard data coverage, marine free‐air gravity anomalies, and vertical gradient gradients are also provided in common data formats.
Key Points
An updated global elevation grid is presented using a spatial sampling interval of 15 arc sec
New bathymetry data include more than 33.6 million ship soundings and more than 6 years of non‐repeat altimetry measurements
The percentage of seafloor mapped by echo soundings remains low; our current compilation covers only 10.84% at 15‐arc sec resolution
The prediction of bathymetry has advanced significantly with the development of satellite altimetry. However, the majority of its data originate from marine gravity anomaly. In this study, based on ...the expression of vertical gravity gradient (VGG) of a rectangular prism, the governing equations for determining sea depths to invert bathymetry. The governing equation is solved by linearization through an iterative process, and numerical simulations verify its algorithm and its stability. We also study the processing methods of different interference errors. The regularization method improves the stability of the inversion process for errors. A piecewise bilinear interpolation function roughly replaces the low-frequency error, and numerical simulations show that the accuracy can be improved by 41.2 % after this treatment. For variable ocean crust density, simulation simulations verify that the root-mean-square (RMS) error of prediction is approximately 5 m for the sea depth of 6 km if density is chosen as the average one. Finally, two test regions in the South China Sea are predicted and compared with ship soundings data, RMS errors of predictions are 71.1 m and 91.4 m, respectively.
One important parameter in estimating the uncertainty of an atom gravimeter is the equivalent height due to the presence of non-negligible vertical gravity gradient. In this article, we report a ...novel method to determine the equivalent height based on the location-dependent Rabi frequency produced by modulating Raman lasers. We theoretically investigate this method and apply it on an atom gravimeter. Experimental results reveal that with this new method, 0.06 <inline-formula> <tex-math notation="LaTeX">\mu </tex-math></inline-formula>Gal uncertainty in gravitational acceleration can be achieved when taking the measurement uncertainty of the equivalent height (<inline-formula> <tex-math notation="LaTeX">0.26247~\pm ~0.00021 </tex-math></inline-formula> m) as the only contribution. This uncertainty is negligible compared with the current state-of-the-art gravity measurement uncertainty of 2-5 <inline-formula> <tex-math notation="LaTeX">\mu </tex-math></inline-formula>Gal. The demonstrated method can be widely applicable in most of the existing atom gravimeters for the evaluation of their equivalent height, especially those for high-precision metrology and fundamental physics test.
In this paper, we construct a new 1′ × 1′ global seafloor topography model, BAT_VGG2021, using the satellite altimetric vertical gravity gradient anomaly model (VGG), SIO curv_30.1.nc, and ship ...soundings. Approximately 74.66 million single-beam depths and more than 180 GB of multibeam grids were downloaded and adopted from the National Centers for Environmental Information (NCEI), Japan Agency for Marine-Earth Science and Technology (JAMSTEC), and Geosciences Australia (GA). The SIO curv_30.1.nc model was used to predict seafloor topography at 15~160 km wavelengths, and ship soundings were used to calibrate topography to VGG ratios. The accuracy of the new BAT_VGG2021 model was assessed by comparing it with ship soundings and existing models. The results indicate that the standard deviation of differences between the predicted model and ship soundings is about 40~80 m, and ~93% of the differences are within 100 m, similar to that of the SIO topo_20.1.nc model. The new BAT_VGG2021 model shows better accuracy than the DTU18BAT, ETOPO1, and GEBCO_08 models, and has been improved significantly from our last model, BAT_VGG2014.
The Solomon Sea Basin is a Cenozoic back‐arc spreading basin within the convergence system of the Pacific and Indo‐Australian plates. Against the background of subduction polarity reversal, the ...current Solomon Sea Basin gradually formed a rhombic morphology with the subduction of the basin along the New Britain Trench and the Trobriand Trough. By analyzing the vertical gravity gradient, natural earthquake and seismic reflection data, this study determines the structural characteristics of the Solomon Sea Basin. It was found that the tectonics of the basin are characterized by the original expansion structure within the central part in addition to the structure induced by the latest subduction along the basin margin. The original spreading structure of the basin presented an east–west linear graben and horst controlled by normal faults during the basin expansion period. As a result of the subduction and slab‐pull of the Solomon Sea Basin, extensional structure belts parallel to the New Britain Trench formed along the basin margin.
Owing to the dependence of algorithms on the measurement of ship soundings and geophysical parameters, the accuracy and coverage of topography still need to be improved. Previous studies have mostly ...predicted topography using gravity or gravity gradient, However, there is a relative lack of integrated research combining or comparing gravity and gravity gradient. In this study, we develop observation equations to predict topography based on vertical gravity anomalies (VG; also called gravity anomalies) and vertical gravity gradient (VGG) anomalies generated by a rectangular prism. The sources of interference are divided into medium- to high-frequency errors and low-frequency errors, and these new methods reduce these errors through regularization and error equations. We also use numerical simulations to test the efficiency of the algorithm and error-reduction method. Statistics show that VGG anomalies are more sensitive to topographic fluctuations; however, the linear correlation between VG anomalies and topography is stronger. Additionally, we use the EIGEN-6C4 model of VG and VGG anomalies to predict topography in shallow and deep-sea areas, with maximum depths of 2 km and 5 km, respectively. In the shallow and deep-sea areas, the root mean square (RMS) errors of VGG anomalies prediction are 93.8 m and 233.8 m, and the corresponding accuracies improved by 7.3% and 2.3% compared with those of VG anomaly prediction, respectively. Furthermore, we use cubic spline interpolation to fuse ship soundings and improve the accuracy of the final topography results. We develop a novel analytical algorithm by constructing an observation equation system applicable to VG and VGG anomalies. This will provide new insights and directions to refine topography prediction based on VG and VGG anomalies.
A New Global Bathymetry Model: STO_IEU2020 Fan, Diao; Li, Shanshan; Feng, Jinkai ...
Remote sensing (Basel, Switzerland),
11/2022, Letnik:
14, Številka:
22
Journal Article
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To address the limitations in global seafloor topography model construction, a scheme is proposed that takes into account the efficiency of seafloor topography prediction, the applicability of ...inversion methods, the heterogeneity of seafloor environments, and the inversion advantages of sea surface gravity field element. Using the South China Sea as a study area, we analyzed and developed the methodology in modeling the seafloor topography, and then evaluated the feasibility and effectiveness of the modeling strategy. Based on the proposed modeling approach, the STO_IEU2020 global bathymetry model was constructed using various input data, including the SIO V29.1 gravity anomaly (GA) and vertical gravity gradient anomaly (VGG), as well as bathymetric data from multiple sources (single beam, multi-beam, seismic, Electronic Navigation Chart, and radar sensor). Five evaluation areas located in the Atlantic and Indian Oceans were used to assess the performance of the generated model. The results showed that 79%, 89%, 72%, 92% and 93% of the checkpoints were within the ±100 m range for the five evaluation areas, and with average relative accuracy better than 6%. The generated STO_IEU2020 model correlates well with the SIO V20.1 model, indicating that the proposed construction strategy for global seafloor topography is feasible.
Over the past decade, the three largest and most destructive earthquakes in recent history with associated tsunamis occurred: the Mw = 9.2 Sumatra-Andamam in 2004, then the Mw = 8.8 Maule in 2010, ...and finally the Mw = 9.1 Tohoku- Oki in 2011. Due to the technological and scientific developments achieved in recent decades, it has been possible to study and model these phenomena with unprecedented resolution and precision. In addition to the coseismic slip models, for which joint inversions of data from various sources are carried out (e.g., teleseismic data, GNSS, INSAR, and Tsunami, among others), depicting the space-time evolution of the rupture, we have high-resolution models of the degree of interseismic coupling (based on GNSS) and also maps of seismic b-value changes. Among these advances, new Earth gravity field models allow mapping densities distribution homogeneously and with a resolution (in wavelengths) of approximately the large rupture areas of great megathrust earthquakes. In this regard, the maximum resolution of GOCE-derived static models is in the order of λ/2≈66 km, while GRACE monthly solutions are in the order of λ/2≈300 km. From the study of the static and dynamic gravitational field, it has been possible to infer mass displacements associated with these events, which have been modeled and compared to the deformation inferred using other methods, yielding very good results. In this work we study the kinematic behavior of the rupture process for one of these largest events, the Mw = 9.1 Tohoku-Oki 2011 earthquake, employing the vertical gradient of gravity derived from the GOCE satellite, finding that the maximum slip occurred close to a lobe of minimum Tzz, as was observed for other case-studies in other subduction-related settings studied in previous works (e.g., the Maule earthquake and the Sumatra-Andaman earthquake, among others). In addition, from the rupture propagation using kinematic models, it can be observed that the rupture is arrested when it approaches high-density structures and, it is enhanced when connecting with lobes of low vertical gravity gradient. We also mapped a block expressed as a low Tzz lobe, developed along the marine forearc, which is controlled by a parallel-to-the-trench normal fault that accommodates subsidence during the interseismic period, as it is coupled with the subducted slab. Then, after rupturing the plate interface, this block is decoupled promoting tectonic inversion and uplift. In this way, the hypothesis that the density structure along the forearc is the ultimate first-order factor that governs the rupture process is reinforced.
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