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Error grid of Scripps Institution of Oceanography (SIO) V31 gravity model over the North Atlantic Ocean.
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Global gravity models from satellite altimetry missions have widely contributed to the improvement of the knowledge over the oceans. However, few models are available with a validated accuracy model, as the most recent models V21 to V32 from Scripps Institution of Oceanography (SIO). The aim of this paper is to propose a method to estimate the accu...
Citations
... edu/ marine_ grav/ mar_ grav. html), University of California in San Diego and Technical University of Denmark (DTU) (Rouxel et al., 2023). Despite the many possibilities, high-resolution seafloor mapping is still lacking (Picard et al., 2017). ...
... [m] are based on the SIO V31 gravity model (Rouxel et al., 2023). Access date: 06 March 2023. ...
The development of reliable seafloor topography models is a complex, multi-track process, which is due to the diversity of available sets of data, their resolution, acquisition methods, complex seafloor forms, and the multitude of interpolation techniques. This article is aimed at assessing the suitability of different algorithms for seafloor modelling based on hybrid datasets (multi-beam soundings and raster GEBCO models). The study involves the selection of optimum solutions as well as a comparative analysis of sea level change trends based on altimetric data. The study area relates to four forms of seafloor topography, namely the oceanic trench, the submarine canyon, the seamount region, and the undulating areas. The most reliable models were built by interpolating by the Kriging methods at a 0.01-degree grid spacing. The smallest residues and the greatest correlation are found between models generated from all available sounding datasets. Raster GEBCO models can be an alternative in the additional model densification. The results show the following relationships: the greater the variation in the topography, the greater the divergence in the values of the sea level change trends. As for sea-mounts, hills, and folds, when the terrain rises rapidly, the trend values also increase and then decrease during the decline. Seafloor structure mapping enables the search for relationships between the seafloor topography and the changes occurring at the water surface.
... mGal in the study area. This accuracy of the altimetric models is consistent with Rouxel et al. (2023), in which they were compared with shipborne gravity data on the Atlantic Ocean. Examination of the statistics of each model series reveals the improvement of the altimetric models as a function of the amount of altimetry data used in their realization. ...
We investigate using the GIRAFE cold-atom gravimeter during an airborne gravity survey for improving gravity field and quasigeoid modelling. The study is conducted over the Bay of Biscay, France. Geoid/quasigeoid determination is usually a major challenge over such coastal areas due to scarce and inconsistent gravity data. In a first step, the GIRAFE dataset is analysed and compared with available surface gravity data as well as with global altimetry models from UCSD and DTU. The comparisons indicate that the DTU model is better than the UCSD model within around 10 km from the coastline. Furthermore, recent satellite altimeter missions significantly improve the altimetry models in coastal areas. A significant bias (− 4.00 mGal) in shipborne data is also found from this comparison. In a second step, eight quasigeoid solutions are calculated to evaluate the contribution of GIRAFE data. This contribution reaches 3 cm in terms of height anomaly for DTU21 while being much larger for UCSDv31 and shipborne data. Finally, the quasigeoid solutions are validated using GNSS-levelling data. The results indicate that using GIRAFE data improves by approximately 50% the quality of quasigeoid models over land near the coast. The highest accuracy, around 1 cm, is achieved when GIRAFE data are merged with refined gravity data. Importantly, the standard deviation is just 1.2 cm when compared with GNSS-levelling points if using only GIRAFE data over marine areas, which is very close to the 1 cm goal of geoid/quasigeoid model determination in modern geodesy. This study thus confirms the benefits of performing airborne gravity survey using quantum sensors.
... Moreover, several studies validated satellite gravity with marine data in different regions of the globe, suggesting that these two datasets are quite comparable with deviations <1 mGal (Guo et al., 2022;Rouxel et al., 2023;Wan et al., 2022;Zaki et al., 2022;Zhang et al., 2021). Therefore, the high-frequency signals in satellite gravity data relate to actual geological features and we used this dataset in our modeling. ...
Propagator wakes within the Juan de Fuca plate represent zones of oceanic crust affected by dynamic readjustments of the spreading centers. They are traditionally mapped from distortions of magnetic anomalies and have been previously interpreted as zones of denser than regular oceanic crust from gravity analysis along several seismic lines in 2-D approximation. In this paper, we utilized a 2.75-D modeling assumption that allowed us to incorporate the effects of the nearby seamounts that were not accounted for in the previous 2-D study. Our analysis reveals that the positive gravity effect of those geological objects was misinterpreted as a need for higher crustal density within propagator wake zones. When seamounts are included in the model, the crust of propagator wakes requires lower densities than the surrounding oceanic crust to explain the observed gravity field. We postulate that the lower densities of propagator wakes relate to faulting during the readjustment of the spreading centers, suggesting that they represent zones of weaker crust.
... In particular, Sandwell et al. (2021) used a very precise marine gravity survey data set in the Gulf of Mexico to compute the median deviation between satellite and marine data sets of 1.33 mGal. Rouxel et al. (2023) compared satellite gravity with several marine gravity surveys over the Atlantic Ocean and concluded a dispersion between data sets within 1 mGal starting from satellite version 23 (we use version 29.1). Therefore, the observed local gravity anomalies such as local gravity lows up to ∼15 mGal and around 10-25 km wide over the known PWs (Figure 2a) are real and require geological explanations. ...
This study aims to explain the nonuniform earthquake pattern along the Cascadia Subduction Zone. In particular, we investigate the relationship between the tectonic features of the subducting oceanic Juan de Fuca slab and the onshore seismicity pattern. We have integrated multiple geophysical data sets toward three general objectives. The first study intends to study variations in physical properties along three 2-dimensional models through regions of different seismicities that combine public gravity, magnetic, and seismic data sets. These models reveal multiple zones of decreased crustal density that we interpret as regions of weaker oceanic crust. The second objective is to delineate major tectonic features by performing spatial analysis of potential fields. The overall methodology comprises gravity and magnetic data filtering, followed by lineaments mapping and cross-referencing interpretation with available seismic reflection data. This process allows delineating zones of crustal weakness by extrapolating outside our three 2-D models. We also map multiple seamounts that appear to cluster along identified zones of weaker crust. Third, we investigate the relationship between the mapped tectonic elements, namely the zones of weak crust with accompanying seamounts, and the observed seismicity trends within the subducted slab. The alignment between those suggests that mapped weak crust zones and associated seamounts may have an influence on the overall subduction process. As more of these structures are heading toward the Washington portion of the margin than to the Oregon portion, more earthquakes are observed in the north than in the south.
... In particular, Sandwell et al. (2021) used a very precise marine gravity survey data set in the Gulf of Mexico to compute the median deviation between satellite and marine data sets of 1.33 mGal. Rouxel et al. (2023) compared satellite gravity with several marine gravity surveys over the Atlantic Ocean and concluded a dispersion between data sets within 1 mGal starting from satellite version 23 (we use version 29.1). Therefore, the observed local gravity anomalies such as local gravity lows up to ∼15 mGal and around 10-25 km wide over the known PWs (Figure 2a) are real and require geological explanations. ...
Out of three oceanic plates subducting beneath North America along the Cascadia Subduction Zone, the Juan de Fuca (JdF) plate is the most intriguing one as it has an unusual seismicity pattern. The two other plates – the Explorer to the north and the Gorda to the south – are associated with a large number of earthquakes along the subduction zone. In contrast, JdF is seismically quiescent, so the inevitable and potentially devastating megathrust earthquake is expected in that region. To understand the tectonic complexity of the JdF subduction, it is important to understand the overall crustal architecture of the margin as well as to know physical properties (densities and magnetic susceptibilities) of the rocks of both oceanic and continental domains. Hence, we performed 2D integrated geophysical modeling along a published seismic reflection profile spanning from the Juan de Fuca spreading ridge to the High Cascades onshore.
In our analysis, we have integrated multiple geophysical data from public sources, namely gravity and magnetic fields with seismic reflections and refractions. Our constructed 2D geophysical model starts from the Axial segment of the JdF spreading ridge. On the western side of the profile, gravity model requires lower densities of the mantle rocks associated with the Cobb hotspot. There are also two bathymetric seamounts near the oceanic ridge that have both gravity and magnetic signatures. Our profile crosses the pseudofault zones that require lower crustal densities with respect to adjacent oceanic crusts. We interpret this as evidence of extensive faulting in that region making the pseudofaults zones of weakness within the JdF plate. Our modeling also suggests the presence of a buried seamount beneath the accretionary prism that appears to be in contact with the Siletz terrane of the continental domain. This buried seamount may potentially influence the overall subduction process and may be related to the lack of earthquakes in this region.
