scholarly journals Controls of the lithospheric thermal field of an ocean-continent subduction zone: the southern Central Andes

2021 ◽  
Author(s):  
Constanz Rodriguez Piceda ◽  
Magdalena Scheck-Wenderoth ◽  
Bott Judith ◽  
Maria Laura Gómez Dacal ◽  
Mauro Cacace ◽  
...  
Keyword(s):  
Subduction Zone ◽  
Thermal Field ◽  
Thermal State ◽  
Flow Distribution ◽  
Central Andes ◽  
S Wave ◽  
Southern Central ◽  
Wave Tomography ◽  
Dip Angle ◽  
Oceanic Slab

In an ocean-continent subduction zone, the assessment of the lithospheric thermal state is essential to determine the controls of the deformation within the upper plate and the dip angle of the subducting lithosphere. In this study, we evaluate the degree of influence of both the configuration of the upper plate and variations of the subduction angle on the lithospheric thermal field of the southern Central Andes (29°–39°S). Here, the subduction angle increases from subhorizontal (5°) north of 33°S, to steep (~30°) in the south. We derived the 3D temperature and heat flow distribution of the lithosphere in the southern Central Andes considering conversion of S wave tomography to temperatures together with steady-state conductive modeling. We found that the orogen is overall warmer than the forearc and the foreland, and that the lithosphere of the northern part of the foreland appears colder than its southern counterpart. Sedimentary blanketing and the thickness of the radiogenic crust exert the main control on the shallow thermal field (< 50 km depth). Specific conditions are present where the oceanic slab is relatively shallow (< 85 km depth) and the radiogenic crust is thin, This configuration results in relatively colder temperatures compared to regions where the radiogenic crust is thick and the slab is steep. At depths >50 km, the temperatures of the overriding plate are mainly controlled by the mantle heat input and the subduction angle. The thermal field of the upper plate likely preserves the flat subduction angle and influences the spatial distribution of shortening.

Unravelling the thermal state of the southern Central Andes and its controlling factors

2021 ◽  
Author(s):  
Constanza Rodriguez Piceda ◽  
Magdalena Scheck-Wenderoth ◽  
Judith Bott ◽  
Maria Laura Gomez Dacal ◽  
Michaël Pons ◽  
...  
Keyword(s):  
Temperature Distribution ◽  
Thermal Field ◽  
Thermal State ◽  
Plate Boundary ◽  
Central Andes ◽  
Tectonic Deformation ◽  
S Wave ◽  
Nazca Plate ◽  
The North ◽  
The Andes

&lt;p&gt;The Andes represent the modern type area for orogeny at a non-collisional, ocean-continent convergent margin. Subduction geometry, tectonic deformation, and seismicity at this plate boundary are closely related to lithospheric temperature distribution in the upper plate. Despite recent advances in the assessment of the thermal state of the Andean lithosphere and adjacent regions derived from geophysical and geochemical studies, several unknowns remain concerning the 3D temperature configuration at lithospheric scale. In particular, it is not clear how both, the configuration of the continental overriding plate (i.e., its thickness and composition) and the variations of the subduction angle of the oceanic Nazca plate influence thermal processes and deformation in the upper plate. To address this issue, we focus on the southern segment of the Central Andes (SCA, 29&amp;#176;S-39&amp;#176;S), where the Nazca plate changes its subduction angle between 33&amp;#176;S and 35&amp;#176;S from the Chilean-Pampean flat-slab zone (&lt; 5&amp;#176; dip, 27-33&amp;#176;S) in the north to a steeper sector south of 33&amp;#176;S (~30&amp;#176; dip). Additionally, the overriding plate exhibits variations in the crustal geometry and density distribution along- and across-strike of the subduction zone. We derived the 3D lithospheric temperature distribution and the surface heat flow of the SCA from the inversion of S-wave velocity to temperatures and calculations of the steady-state conductive thermal field. The configuration of the region &amp;#8211; concerning both, the heterogeneity of the lithosphere and the slab dip &amp;#8211; was accounted for by incorporating a 3D data-constrained structural and density model of the SCA into the workflow. We conclude that the generated thermal model allows us to evaluate how mantle thermal anomalies and first-order structural and lithological heterogeneities in the lithosphere, observed across and along-strike of Andean orogen, affect the thermal field of the SCA and thus the propensity of the South American lithosphere to specific styles in deformation. In addition, our results are useful to constrain thermo-mechanical simulations in geodynamic modelling and therefore, contribute to a better understanding of the present-day rheological state of the Andes and adjacent regions.&lt;/p&gt;

Crustal model of the Southern Central Andes derived from ambient seismic noise Rayleigh-wave tomography

2018 ◽  
Vol 744 ◽  
pp. 215-226 ◽  
Author(s):  
Diego González-Vidal ◽  
Anne Obermann ◽  
Andrés Tassara ◽  
Klaus Bataille ◽  
Matteo Lupi
Keyword(s):  
Rayleigh Wave ◽  
Seismic Noise ◽  
Central Andes ◽  
Ambient Seismic Noise ◽  
Crustal Model ◽  
Southern Central ◽  
Wave Tomography ◽  
Rayleigh Wave Tomography

Mantle dynamics of the Andean Subduction Zone from continent-scale teleseismic S-wave tomography

2020 ◽  
Vol 224 (3) ◽  
pp. 1553-1571
Author(s):  
Emily E Rodríguez ◽  
Daniel Evan Portner ◽  
Susan L Beck ◽  
Marcelo P Rocha ◽  
Marcelo B Bianchi ◽  
...  
Keyword(s):  
South America ◽  
Subduction Zone ◽  
Lower Mantle ◽  
Subduction Zones ◽  
Seismic Velocity ◽  
High Amplitude ◽  
S Wave ◽  
Nazca Plate ◽  
Wave Tomography ◽  
Andean Subduction

SUMMARY The Andean Subduction Zone is one of the longest continuous subduction zones on Earth. The relative simplicity of the two-plate system has makes it an ideal natural laboratory to study the dynamics in subduction zones. We measure teleseismic S and SKS traveltime residuals at &gt;1000 seismic stations that have been deployed across South America over the last 30 yr to produce a finite-frequency teleseismic S-wave tomography model of the mantle beneath the Andean Subduction Zone related to the Nazca Plate, spanning from ∼5°N to 45°S and from depths of ∼130 to 1200 km. Within our model, the subducted Nazca slab is imaged as a fast velocity seismic anomaly. The geometry and amplitude of the Nazca slab anomaly varies along the margin while the slab anomaly continues into the lower mantle along the entirety of the subduction margin. Beneath northern Brazil, the Nazca slab appears to stagnate at ∼1000 km depth and extend eastward subhorizontally for &gt;2000 km. South of 25°S the slab anomaly in the lower mantle extends offshore of eastern Argentina, hence we do not image if a similar stagnation occurs. We image several distinct features surrounding the slab including two vertically oriented slow seismic velocity anomalies: one beneath the Peruvian flat slab and the other beneath the Paraná Basin of Brazil. The presence of the latter anomaly directly adjacent to the stagnant Nazca slab suggests that the plume, known as the Paraná Plume, may be a focused upwelling formed in response to slab stagnation in the lower mantle. Additionally, we image a high amplitude fast seismic velocity anomaly beneath the Chile trench at the latitude of the Sierras Pampeanas which extends from ∼400 to ∼1000 km depth. This anomaly may be the remnants of an older, detached slab, however its relationship with the Nazca–South America subduction zone remains enigmatic.

RETROARC BASIN REORGANIZATION AND DIACHRONOUS ARIDIFICATION DURING PALEOGENE UPLIFT OF THE SOUTHERN CENTRAL ANDES

2016 ◽  
Author(s):  
Julie C. Fosdick ◽  
◽  
Barbara Carrapa ◽  
Barbara Carrapa ◽  
Ellen J. Reat ◽  
...  
Keyword(s):  
Central Andes ◽  
Southern Central

A COUPLED LACUSTRINE AND ALLUVIAL FAN RECORD FOR THE HOLOCENE OF THE ARID SOUTHERN CENTRAL ANDES

2017 ◽  
Author(s):  
José Luis Antinao ◽  
◽  
Rachel Tiner ◽  
Rachel Tiner ◽  
Rachel Tiner ◽  
...  
Keyword(s):  
Central Andes ◽  
Alluvial Fan ◽  
The Holocene ◽  
Southern Central

scholarly journals Plate Coupling Mechanism of the Central Andes Subduction: Insight from Gravity Model

2019 ◽  
Vol 9 (1) ◽  
pp. 13-21
Author(s):  
Rezene Mahatsente
Keyword(s):  
Subduction Zone ◽  
Continental Crust ◽  
Gravity Model ◽  
Central Andes ◽  
High Density ◽  
Seismic Gap ◽  
Coupling Mechanism ◽  
Crust And Upper Mantle ◽  
Velocity Models ◽  
Plate Coupling

Abstract The Central Andes experienced major earthquake (Mw =8.2) in April 2014 in a region where the giant 1877 earthquake (Mw=8.8) occurred. The 2014 Iquique earthquake did not break the entire seismic gap zones as previously predicted. Geodetic and seismological observations indicate a highly coupled plate interface. To assess the locking mechanism of plate interfaces beneath Central Andes, a 2.5-D gravity model of the crust and upper mantle structure of the central segment of the subduction zone was developed based on terrestrial and satellite gravity data from the LAGEOS, GRACE and GOCE satellite missions. The densities and major structures of the gravity model are constrained by velocity models from receiver function and seismic tomography. The gravity model defined details of crustal and slab structure necessary to understand the cause of megathrust asperity generation. The densities of the upper and lower crust in the fore-arc (2970 – 3000 kg m−3) are much higher than the average density of continental crust. The high density bodies are interpreted as plutonic or ophiolitic structures emplaced onto continental crust. The plutonic or ophiolitic structures may be exerting pressure on the Nazca slab and lock the plate interfaces beneath the Central Andes subduction zone. Thus, normal pressure exerted by high density fore-arc structures and buoyancy force may control plate coupling in the Central Andes. However, this interpretation does not exclude other possible factors controlling plate coupling in the Central Andes. Seafloor roughness and variations in pore-fluid pressure in sediments along subduction channel can affect plate coupling and asperity generation.

scholarly journals Responses of dipole-source reflected shear waves in acoustically slow formations

2019 ◽  
Author(s):  
Hao Wang ◽  
Ning Li ◽  
Caizhi Wang ◽  
Hongliang Wu ◽  
Peng Liu ◽  
...  
Keyword(s):  
Finite Difference Time Domain ◽  
Dipole Source ◽  
Sh Wave ◽  
S Wave ◽  
High Fracture ◽  
S Waves ◽  
Angle Fracture ◽  
Dip Angle ◽  
Difference Time

Abstract In the process of dipole-source acoustic far-detection logging, the azimuth of the fracture outside the borehole can be determined with the assumption that the SH–SH wave is stronger than the SV–SV wave. However, in slow formations, the considerable borehole modulation highly complicates the dipole-source radiation of SH and SV waves. A 3D finite-difference time-domain method is used to investigate the responses of the dipole-source reflected shear wave (S–S) in slow formations and explain the relationships between the azimuth characteristics of the S–S wave and the source–receiver offset and the dip angle of the fracture outside the borehole. Results indicate that the SH–SH and SV–SV waves cannot be effectively distinguished by amplitude at some offset ranges under low- and high-fracture dip angle conditions, and the offset ranges are related to formation properties and fracture dip angle. In these cases, the fracture azimuth determined by the amplitude of the S–S wave not only has a $180^\circ $ uncertainty but may also have a $90^\circ $ difference from the actual value. Under these situations, the P–P, S–P and S–S waves can be combined to solve the problem of the $90^\circ $ difference in the azimuth determination of fractures outside the borehole, especially for a low-dip-angle fracture.

scholarly journals S wave attenuation structure on the western side of the Nankai subduction zone: Implications for fluid distribution and dynamics

2014 ◽  
Vol 119 (10) ◽  
pp. 7805-7822 ◽  
Author(s):  
Tsutomu Takahashi ◽  
Koichiro Obana ◽  
Yojiro Yamamoto ◽  
Ayako Nakanishi ◽  
Shuichi Kodaira ◽  
...  
Keyword(s):  
Subduction Zone ◽  
Wave Attenuation ◽  
Fluid Distribution ◽  
S Wave ◽  
Nankai Subduction Zone ◽  
Attenuation Structure ◽  
Western Side
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