Gravity anomaly and crustal density structure in Jilantai rift zone and its adjacent region

3-D density structure of the upper-mantle from gravity inversion constrained by seismic velocity model: A case study of the Mediterranean Sea and surrounding region &#160;Harash Fayez1, Chao Chen1,2, Qing Liang1,2, Chenming Tu11Institute of Geophysics & Geomatics, China University of Geosciences, Wuhan 430074, P.R. China (Corresponding &#160;author: &#160;Harash Fayez).2Subsurface Multi-Scale Imaging Lab, Institute of Geophysics & Geomatics, China University of Geosciences,&#160;Wuhan 430074, P.R. China.&#160;Summary A 3-D density structure of the lithosphere and upper-mantle beneath the Mediterranean Sea and adjacent region was constructed based on inversion of gravity anomaly constrained by seismic tomography model. In this study, we have removed the terrain and crustal effects from the observed gravity field (EIGEN-6C4), in order to obtain the mantle gravity anomaly which was used to investigate the lithospheric and the upper-mantle density distribution. The 3-D inversion process is constrained by a reference density model estimated from shear-wave velocity model (SL2013sv). Our result shows some characteristics of density distribution in the lithosphere and upper-mantle that might be related to the tectonic signification beneath the Mediterranean Sea and adjacent region. A low-density zone dominates the lithosphere beneath the Mediterranean Sea except the area around Arabia shield and North Anatolian fault belt. A thinner high-density layer appears beneath the southwest of Mediterranean Sea, and it may be related to the older oceanic lithosphere fragments. The high-density anomalies appear below depth of 280 km beneath the Mediterranean Sea and the Turkish Aegean Sea Plate. However, the low-density anomalies appears at the top of the upper-mantle beneath trenches of the southwestern of Mediterranean Sea, the eastern of Aegean Sea, the Red Sea, the Black Sea and the middle of Arabia shield. It may indicate the intensity and origination of tectonic movement referring the deep structure below the Eratosthenes seamount in the Mediterranean Sea. Furthermore, the convergence region of two low-density anomaly zones may be interpreted as a significant tectonic unit.&#160;

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Crustal density structure in northwestern South America derived from analysis and 3-D modeling of gravity and seismicity data

Tectonophysics ◽

10.1016/j.tecto.2014.07.026 ◽

2014 ◽

Vol 634 ◽

pp. 97-115 ◽

Cited By ~ 21

Author(s):

J. Sanchez-Rojas ◽

M. Palma

Keyword(s):

South America ◽

Density Structure ◽

Crustal Density

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Crustal density structure of the Antarctic continent from constrained 3-D gravity inversion

10.5194/egusphere-egu2020-4427 ◽

2020 ◽

Author(s):

Fei Ji ◽

Qiao Zhang

Keyword(s):

Gravity Inversion ◽

Inversion Method ◽

Rift System ◽

Low Density ◽

Density Structure ◽

West Antarctica ◽

The West ◽

Antarctic Continent ◽

Crustal Density ◽

The Antarctic

Crustal density is a fundamental physical parameter that helps to reveal its composition and structure, and is also significantly related to the tectonic evolution and geodynamics. Based on the latest Bouguer gravity anomalies and the constrains of 3-D shear velocity model and surface heat flow data, the 3-D gravity inversion method, incorporating deep weight function, has been used to obtain the refined density structure over the Antarctic continent. Our results show that the density anomalies changes from -0.25 g/cm3 to 0.20 g/cm3. Due to the multi-phase extensional tectonics in Mesozoic and Cenozoic, the low density anomalies dominates in the West Antarctica, while the East Antarctica is characterized by high values of density anomalies. By comparing with the variations of effective elastic thickness, the inverted density structure correlates well with the lithospheric integrated strength. According to the mechanical strength and inverted density structure in the West Antarctic Rift System (WARS), our analysis found that except for the local area affected by the Cenozoic extension and magmatic activity, the crustal thermal structure in the WARS tends to be normal under the effect of heat dissipation. Finally, the low density anomalies features in West Antarctica extend to beneath the Transantarcitc Mountains (TAMs), however, we hypothesize that a single rift mechanism seems not be used to explain the entire TAMs range.

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An analysis of the crust–mantle boundary in Hudson Bay from gravity and seismic observations

Canadian Journal of Earth Sciences ◽

10.1139/e68-127 ◽

1968 ◽

Vol 5 (5) ◽

pp. 1297-1303 ◽

Cited By ~ 4

Author(s):

J. R. Weber ◽

A. K. Goodacre

Keyword(s):

Gravity Anomaly ◽

Gravity Anomalies ◽

Gravitational Effect ◽

Compressional Wave ◽

Seismic Survey ◽

Hudson Bay ◽

Mantle Boundary ◽

Crustal Velocity ◽

Velocity Variations ◽

Crustal Density

A study of the results of the gravity and seismic surveys in Hudson Bay in 1965 has shown that the gravitational effect of a two-layer model based on the seismically determined depths has no correlation with the observed gravity anomalies. On the profile from Churchill to Povungnituk the gravity and seismic observations can be reconciled by postulating lateral variations of the acoustic compressional wave velocity within the crust. A crustal model has been calculated—using the same time-terms and the same mean crustal velocity—whose gravitational effect fits the observed gravity. The velocity varies from 6.15 to 6.56 km/s and the postulated depths are almost entirely within the confidence limits of the original model.In order to test the hypothesis, the postulated velocity variations have been compared with the lower refractor velocities of the shallow seismic survey, based on the assumption that the crustal velocities ought to be systematically higher than the crystalline surface velocities and that there may be a correlation between variations in crustal and surface velocities. The test is inconclusive because bottom refractor velocities are higher than crustal velocities in two areas where volcanic flows and high-velocity sediments may be present.The case of linearly related velocity (V) and density (ρ) variations has been analyzed and it is shown that the gravitational effect of the crust–mantle boundary undulations may be completely masked or even overbalanced by density changes in the crust if [Formula: see text]. The crust can be characterized by having dominant velocity variations (in which case the gravity anomaly reflects the undulations of the crust–mantle boundary) or dominant density variations (in which case the gravity anomaly inversely reflects the crust–mantle boundary undulations) depending on the relationship between average crustal density and average crustal velocity.

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