GRACE Data Explore Moho Change Characteristics Beneath the South America Continent near the Chile Triple Junction

Pengchao Sun,Changsheng Guo,Dongping Wei

doi:10.3390/rs14040924

Abstract

The internal and external mass migration and redistribution of the Earth system are usually accompanied by changes in the gravity field, and the Gravity Recovery and Climate Experiment (GRACE) has been proven to be able to effectively monitor and evaluate such changes. The Chile Triple Junction (CTJ) is the convergence point of the Nazca plate, the Antarctic plate and the South American plate. Subductions of different forms and rates in the north and south of the CTJ have varying degrees of impact on the surface and underground material changes of the South American plate. In this study, GRACE data are used in the estimation of the comprehensive mass changes in the South America Continent (SAC) Near the CTJ (~15° range). In addition, surface movement changes constrained by GNSS data cannot fully explain the GRACE results after deducting hydrological information, which indicates that residual signals might be attributed to mass changes beneath the crust, that is, the Moho interface deformation. After eliminating surface movement and hydrological signals from the comprehensive mass changes of GRACE, this study obtains the deep structural information and calculates the Moho changes of three significant regions with rates of −2.12 ± 0.67 cm/yr, 0.18 ± 0.19 cm/yr and −6.46 ± 1.31 cm/yr, respectively. Results have demonstrated that the subductions of the Nazca plate and the Antarctica plate have an effect on the uneven deformation of the Moho interface beneath the SAC. The Moho beneath the SAC mainly shows a deepening trend, but it is uplifted in some areas north of CTJ. On the whole, the rate of Moho changes is greater in the south than in the north. The relationship between Moho changes and surface changes also indicates that a longer timescale may be needed for maintaining isostatic balance.

Highlights

Published: 14 February 2022The Chile Triple Junction (CTJ) is formed by the Subduction of the Chile ridge (NazcaAntarctic spreading center) beneath the South American plate [1,2,3]
snow water equivalent (SWE) result from Water GAP Hydrological Model (WGHM) is shown in Figure 6e, and the SWE result in Figure 6f is provided by the Global Land Data Assimilation System (GLDAS) model
The South America Continent (SAC) is subject to the rapid eastward subduction of the Nazca plate in northern CTJ, whereas in the south, the Antarctic plate is subducted at a low speed with an expanding ridge

Summary

Introduction

The Chile Triple Junction (CTJ) is formed by the Subduction of the Chile ridge (NazcaAntarctic spreading center) beneath the South American plate [1,2,3]. Since 17 Ma, a series of South Chile Ridge (SCR) segments parallel to the trench have subducted in the southern. Subduction in the northern part of the CTJ is associated with the formation of lower South American topography (~2300 m elevation), a small number of Cenozoic molasse sedimentary rocks in the east, and results in the lack of a fold and thrust. Subduction in the southern part of the CTJ is associated with higher topography (~4000 m elevation) with exhumed Patagonian batholith and pre-Jurassic rocks, the late Cenozoic molasse deposits and the development of a fold and thrust belt which

Results

Discussion

Conclusion