In this paper, we construct a new 1′ $\times$ 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.

A new one-minute global seafloor topography model was derived from vertical gravity gradient anomalies (VGG), altimetric gravity anomalies, and ship soundings. Ship soundings are used to constrain seafloor topography at wavelengths longer than 200 km and to calibrate the topography to VGG (or gravity) ratios at short wavelengths area by area. VGG ratios are used to predict seafloor topography for wavelength bands of 100–200 km and to suppress the effect of crust isostasy. Gravity anomalies are used to recover seafloor topography at wavelengths shorter than 100 km. The data processing procedure is described in detail in this paper. The accuracy of the model is evaluated using ship soundings and existing models, including General Bathymetric Charts of the Oceans (GEBCO), DTU10, ETOPO1, and SIO V15.1. The results show that, in the discussed regions, the accuracy of the model is better than ETOPO1, GEBCO, and DTU10. Additionally, the model is comparable with V15.1, which is generally believed to have the highest accuracy. In the north-central Pacific Ocean, the accuracy of the model increased by approximately 29.5% compared with the V15.1 model. This indicates that a more accurate seafloor topography model can be formed by combining gravity anomalies, VGG, and ship soundings.

New bathymetry models in the northwestern Pacific Ocean are presented at 1 arc-minute and 15 arc-second resolution. The latest version of the altimetric vertical gravity gradient (VGG) anomalies from Scripps Institute of Oceanography, ∼7 million single-beam depths from the National Centers for Environmental Information, and ∼80 GB of multibeam grids from the Japan Agency for Marine-Earth Science and Technology are used. The ship-board depths are used to constrain bathymetry at wavelengths longer than 200 km, and calibrate the local topography to VGG ratio at 15–200 km wavelength bands. The VGG is used to predict bathymetry at 15 ∼ 200 km wavelength bands. The spectrum analysis results show that the 1 arc-minute model has more power than models predicted from gravity anomalies at wavelengths shorter than 100 km. The standard deviation of differences between the 1 arc-minute model and ship-board depths is 44.76 m, and it is 102.842 m comparing to the SIO topo_20.1.nc model. The accuracy of the new 1 arc-minute model has been improved significantly from our last bathymetry model, BAT_VGG, and has a better accuracy than that of the DTU18, GEBCO_08, and ETOPO1 models. The accuracy of the 15 arc-second model is consistent with that of SRTM + V2.1 and GEBCO_2020.

We applied a 2-dimensional, non-spectral technique to investigate the spatial variations of the lithospheric effective elastic thickness (T_e) in the eastern Bayan Har block and its adjacent areas. T_e values were determined by comparison of observed and flexural modelled Bouguer gravity anomalies. The results suggested that T_e vary significantly from eastern Tibet to the Sichuan basin. The eastern Bayan Har block and northern Sichuan-Yunan block had low T_e (0<T_e<20km), indicated easily deformable lithosphere. The Sichuan basin had high T_e (40km<T_e<100km), and acted as a rigid block which resisted the eastward extrusion of plateau materials. Moderate T_e (30km<T_e<40km) under the Longmen Shan fault belt indicated that the lithosphere of the Sichuan basin plays an important role in supporting the Longmen Shan topography. The extremely low T_e (T_e<10km) in the seismogenic zone of the Ms7.0 Jiuzhaigou earthquake indicated that the topography is compensated locally, different from the Longmen Shan significantly. A banded relatively low T_e (<40km) region stretched from northeastern Bayan Har block to southwestern Ordos block sketches out a plateau material escaping channel, questions the exiting of crustal flow in the north side of the Sichuan basin.