The nature of the North-South change of the magnitude of tectonic shortening in Central Andes at Altiplano-Puna latitudes: a thermomechanical modeling approach.

2020 ◽  
Author(s):  
Michaël Pons ◽  
Stephan Sobolev
Keyword(s):  
Cross Sections ◽  
Pure Shear ◽  
Foreland Basin ◽  
Central Andes ◽  
South American ◽  
Nazca Plate ◽  
South American Plate ◽  
The Andes ◽  
Subduction System ◽  
Roll Back

<p><span>The Andean orogeny is a subduction-type orogeny, the oceanic Nazca Plate sinks under the continental South American Plate. While the subduction has been active since ~180 Ma, the shortening of the Andes initiated at ~50 Ma or less.</span></p><p><span>In a oceanic-continental subduction system, the absolute velocity of the overriding-plate (OP) largely controls the style of subduction (stable, advancing, retreating), the geometry of the slab (dipping angle, curvature) and the style of deformation (shortening or spreading) within the OP. In the case of the Central Peru-Chile subduction, the South American plate is advancing westwards whereas the Nazca plate is anchored into the transition zone (~660 km). As a consequence, the trench is forced to retreat and the Nazca plate to roll-back. The dip of the slab decreases meanwhile the Andes experienced a maximum shortening of ~300 km at ~19-21°S latitudes.</span></p><p><span>Previous study have shown that the strain localizes within areas of low strength and low gravitational potential of energy. In central Andes, weakening mechanisms of the OP such as lithospheric delamination have intensified the magnitude of tectonic shortening and contributed to formation of the Altiplano-Puna plateau. The deformation between the plateau and the foreland occurs in the form of pure shear or simple shear and is expressed in terms of different tectonic styles in the foreland basin, thick-skinned (e.g the Puna) and thin-skinned (e.g the Altiplano), respectively. Nevertheless, the influence of the strength variations of the OP on the subduction dynamics in the case of the central Andes has been </span><span>poorly</span><span> explored so far. Our hypothesis is that lateral variations of OP strength result in variable rates of trench roll-back. To test it, we have built 2D high-resolution E-W cross sections along the Altiplano and Puna latitudes (12-27°S) including the subduction of the Nazca plate. For that purpose, we used the FEM geodynamic code ASPECT. Our model includes visco-plastic rheology in addition to gabbro-eclogite phase transition. These preliminary results contribute to the discussion on the nature of the magnitude of shortening in a subduction system. They are also a first step to derive a 3D model of the entire region and to consider additional surface processes such as erosion, transportation and sedimentation. </span></p>

What drives orogeny in the Andes?

Geology ◽  
2005 ◽  
Vol 33 (8) ◽  
pp. 617-620 ◽  
Author(s):  
S.V. Sobolev ◽  
A.Y. Babeyko
Keyword(s):  
Friction Coefficient ◽  
Crustal Structure ◽  
South American ◽  
The South ◽  
Nazca Plate ◽  
South American Plate ◽  
The Andes ◽  
Continental Lower Crust ◽  
Sediment Cover

Abstract The Andes, the world's second highest orogenic belt, were generated by the Cenozoic tectonic shortening of the South American plate margin overriding the subducting Nazca plate. We use a coupled thermomechanical numerical modeling technique to identify factors controlling the intensity of the tectonic shortening. From the modeling, we infer that the most important factor was accelerated westward drift of the South American plate; changes in the subduction rate were less important. Other important factors are crustal structure of the overriding plate and shear coupling at the plates' interface. The model with a thick (40–45 km at 30 Ma) South American crust and relatively high friction coefficient (0.05) at the Nazca–South American interface generates >300 km of tectonic shortening during 30–35 m.y. and replicates the crustal structure and evolution of the high central Andes. The model with an initially thinner (<40 km) continental crust and lower friction coefficient (<0.015) results in <40 km of South American plate shortening, replicating the situation in the southern Andes. Our modeling also demonstrates the important role of the processes leading to mechanical weakening of the overriding plate during tectonic shortening, such as lithospheric delamination, triggered by the gabbro-eclogite transformation in the thickened continental lower crust, and mechanical failure of the sediment cover at the shield margin.

Study for the Determination of Seismic Hazard for the Ocensa Oil Pipeline

2015 ◽  
Author(s):  
Julian Javier Corrales ◽  
Hugo Alberto García ◽  
Mauricio Gallego Silva ◽  
Elkin Gerardo Avila
Keyword(s):  
Seismic Hazard ◽  
Oil Fields ◽  
Mountain Range ◽  
South American ◽  
Nazca Plate ◽  
South American Plate ◽  
Oil Pipeline ◽  
The Andes ◽  
The Caribbean

The Andes mountain range crosses South America from South to North, is created by the subduction of the Nazca plate beneath the South American plate, this situation generates a high seismic and volcanic activity which have been decisive in shaping the relief of the continent. The OCENSA pipeline crosses the Andes Mountains on its way to transport crude from the oil fields of the eastern plains to the port of Coveñas on the Caribbean Sea. Therefore for the integrity department of Ocensa the assessment of seismic hazard is among one of its priorities. In this paper the results of the study in Ocensa for determination of seismic hazard for the pipeline and its major facilities are presented.

scholarly journals Basement composition and basin geometry controls on upper-crustal deformation in the Southern Central Andes (30–36°S)

2016 ◽  
Vol 153 (5-6) ◽  
pp. 945-961 ◽  
Author(s):  
JOSÉ F. MESCUA ◽  
LAURA GIAMBIAGI ◽  
MATÍAS BARRIONUEVO ◽  
ANDRÉS TASSARA ◽  
DIEGO MARDONEZ ◽  
...  
Keyword(s):  
Central Andes ◽  
Nazca Plate ◽  
The Andes ◽  
Structural Style ◽  
Thrust Belts ◽  
Southern Central ◽  
History Of ◽  
Basin Geometry ◽  
Subduction System ◽  
Different Parts

AbstractDeformation and uplift in the Andes are a result of the subduction of the Nazca plate below South America. The deformation shows variations in structural style and shortening along and across the strike of the orogen, as a result of the dynamics of the subduction system and the features of the upper plate. In this work, we analyse the development of thin-skinned and thick-skinned fold and thrust belts in the Southern Central Andes (30–36°S). The pre-Andean history of the area determined the formation of different basement domains with distinct lithological compositions, as a result of terrane accretions during Palaeozoic time, the development of a widespread Permo-Triassic magmatic province and long-lasting arc activity. Basin development during Palaeozoic and Mesozoic times produced thick sedimentary successions in different parts of the study area. Based on estimations of strength for the different basement and sedimentary rocks, calculated using geophysical estimates of rock physical properties, we propose that the contrast in strength between basement and cover is the main control on structural style (thin- v. thick-skinned) and across-strike localization of shortening in the study area.

Tsunami and Seismic Damage Caused by the Earthquake Off Iquique, Chile, in April, 2014

2016 ◽  
Vol 10 (02) ◽  
pp. 1640003 ◽  
Author(s):  
Takashi Tomita ◽  
Kentaro Kumagai ◽  
Cyril Mokrani ◽  
Rodrigo Cienfuegos ◽  
Hisashi Matsui
Keyword(s):  
Seismic Damage ◽  
South American ◽  
Nazca Plate ◽  
South American Plate ◽  
Straight Line ◽  
Earthquake Resistant ◽  
Straight Line Distance ◽  
Run Up ◽  
Tsunami Run Up ◽  
The City

On Tuesday, April 1, 2014, at 8:46 p.m. local time in Chile, a subduction earthquake of Mw 8.2 occurred about 100[Formula: see text]km northwest of the city of Iquique, where the Nazca plate subducts beneath the South American plate. This earthquake triggered a tsunami, which hit coastal areas in northern Chile. A joint Japan–Chile team conducted a post-tsunami field survey to measure the height of the tsunami traces and to investigate the damage caused by the earthquake and tsunami. Based on measurements of the tsunami traces, it is estimated that a tsunami 3–4[Formula: see text]m in height hit the coast from Arica, which is near the border between Chile and Peru, to Patache, south of Iquique, a straight-line distance of approximately 260[Formula: see text]km. The tsunami caused only minor inundations near shorelines, and caused no damage to buildings because living spaces were higher than the tsunami run-up height. Seismic damage was more extensive than that caused by the tsunami, especially in Iquique, and included the destruction of houses, buildings, and other infrastructure. It also ignited fires. In the Port of Iquique, a wharf, before earthquake-resistant improvements were implemented, was destroyed by the strong ground motions that resulted from the earthquake.

Lithospheric density structure of the Southern Central Andes and their forelands constrained by 3D gravity modelling

2020 ◽  
Author(s):  
Constanza Rodriguez Piceda ◽  
Magdalena Scheck-Wenderoth ◽  
Maria Laura Gómez Dacal ◽  
Judith Bott ◽  
Claudia Prezzi ◽  
...  
Keyword(s):  
Central Andes ◽  
Crustal Thickening ◽  
Velocity Variation ◽  
Mountain Range ◽  
South American ◽  
The South ◽  
Complex Deformation ◽  
Nazca Plate ◽  
Southern Central ◽  
The Relationship

&lt;p&gt;The Andean orogeny is a ~7000 km long N-S trending mountain range developed along the South American western margin. The formation of this mountain range is driven by the subduction of the oceanic Nazca plate beneath the continental South American plate, being the only known present-day case of subduction-type orogeny. In this tectonic setting, the intrinsic physical properties of the overriding plate govern the formation of zones of crustal strength and weakness and control the localization and the style of deformation. Furthermore, the dynamics of the subducting oceanic lithosphere is strongly conditioned by the properties of the continental counterpart. The southern segment of the Central Andes (29&amp;#176;S-39&amp;#176;S) is a suitable scenario to investigate the relationship between the two plates for several reasons. It is characterized by a complex deformation pattern with variations in horizontal shortening, crustal thickening and mean topographic elevation. In addition, the subduction angle changes at 33&amp;#176;S-35&amp;#176;S latitude from flat in the North to normal in the South. To gain insight into this geodynamic system, a detailed characterization of the lithosphere is needed. Therefore, we constructed a 3D model of the entire segment of the Southern Central Andes that is consistent with the available geological, seismic and gravity data in order to assess the geometry and density variation within the lithosphere. The derived configuration shows a spatial correlation between density domains and known tectonic features. It is also consistent with other independent observations such as S wave velocity variation and surface deformation. The generated structural model allows us to reach the first conclusions about the relationship between the characteristics of the overriding plate and the crustal deformation and dynamics of the subduction system. It is also useful to constrain thermomechanical experiments and therefore contributes to discussions about the crustal thermal and rheological fields within the region.&lt;/p&gt;

scholarly journals Measuring the seismic risk along the Nazca-Southamerican subduction front: Shannon entropy and mutability

2019 ◽  
Author(s):  
Eugenio E. Vogel ◽  
Felipe G. Brevis ◽  
Denisse Pastén ◽  
Víctor Muñoz ◽  
Rodrigo A. Miranda ◽  
...  
Keyword(s):  
Shannon Entropy ◽  
Seismic Risk ◽  
Background Activity ◽  
Large Earthquake ◽  
South American ◽  
The South ◽  
Nazca Plate ◽  
South American Plate ◽  
Major Earthquake ◽  
Similarities And Differences

Abstract. Four geographical zones are defined along the trench that is formed due to the subduction of the Nazca Plate underneath the South American plate; they are denoted A, B, C and D from North to South; zones A, B and D have had a major earthquake after 2010 (8.0), while zone C has not, thus offering a contrast for comparison. For each zone a sequence of intervals between consecutive seisms with magnitudes ≥ 3.0 is formed and then characterized by Shannon entropy and mutability. These methods show correlation after a major earthquake in what is known as the aftershock regime but they show independence otherwise. Exponential adjustments for these parameters reveal that mutability offers a wider range for the parameters characterizing the recovery to the values of the parameters defining the background activity for each zone before a large earthquake. It is found that the background activity is particularly high for zone A, still recovering for Zone B, reaching values similar to those of Zone A in the case of Zone C (without recent major earthquake) and oscillating around moderate values for Zone D. It is discussed how this can be an indication for more risk of an important future seism in the cases of Zones A and C. The similarities and differences between Shannon entropy and mutability are discussed and explained.

scholarly journals Measuring the seismic risk along the Nazca-Southamerican subduction front: Shannon entropy and mutability

2020 ◽  
Author(s):  
Eugenio E. Vogel ◽  
Felipe G. Brevis ◽  
Denisse Pastén ◽  
Víctor Muñoz ◽  
Rodrigo A. Miranda ◽  
...  
Keyword(s):  
Shannon Entropy ◽  
Seismic Risk ◽  
Background Activity ◽  
Large Earthquake ◽  
South American ◽  
Nazca Plate ◽  
South American Plate ◽  
Major Earthquake ◽  
Similarities And Differences ◽  
Set Up

Abstract. Four geographical zones are defined along the trench that is formed due to the subduction of the Nazca Plate underneath the South American plate; they are denoted A, B, C and D from North to South; zones A, B, and D had a major earthquake after 2010 (Magnitude over 8.0), while zone C has not, thus offering a contrast for comparison. For each zone a sequence of intervals between consecutive seisms with magnitudes ≥ 3.0 is set up and then characterized by Shannon entropy and mutability. These methods show correlation after a major earthquake in what is known as the aftershock regime, but show independence otherwise. Exponential adjustments for these parameters reveal that mutability offers a wider range for the parameters characterizing the recovery compared to the values of the parameters defining the background activity for each zone before a large earthquake. It is found that the background activity is particularly high for zone A, still recovering for zone B, reaching values similar to those of zone A in the case of zone C (without recent major earthquake) and oscillating around moderate values for zone D. It is discussed how this can be an indication for more risk for an important future seism in the cases of zones A and C. The similarities and differences between Shannon entropy and mutability are discussed and explained.

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;

scholarly journals GNSS Constraints to Active Tectonic Deformations of the South American Continental Margin in Ecuador

Sensors ◽  
2021 ◽  
Vol 21 (12) ◽  
pp. 4003
Author(s):  
José Tamay ◽  
Jesús Galindo-Zaldivar ◽  
John Soto ◽  
Antonio J. Gil
Keyword(s):  
Subduction Zone ◽  
Main Tool ◽  
South American ◽  
The South ◽  
Nazca Plate ◽  
South American Plate ◽  
The North ◽  
The Pacific ◽  
Active Tectonic ◽  
Plate Subduction

GNSS observations constitute the main tool to reveal Earth’s crustal deformations in order to improve the identification of geological hazards. The Ecuadorian Andes were formed by Nazca Plate subduction below the Pacific margin of the South American Plate. Active tectonic-related deformation continues to present, and it is constrained by 135 GPS stations of the RENAGE and REGME deployed by the IGM in Ecuador (1995.4–2011.0). They show a regional ENE displacement, increasing towards the N, of the deformed North Andean Sliver in respect to the South American Plate and Inca Sliver relatively stable areas. The heterogeneous displacements towards the NNE of the North Andean Sliver are interpreted as consequences of the coupling of the Carnegie Ridge in the subduction zone. The Dolores–Guayaquil megashear constitutes its southeastern boundary and includes the dextral to normal transfer Pallatanga fault, that develops the Guayaquil Gulf. This fault extends northeastward along the central part of the Cordillera Real, in relay with the reverse dextral Cosanga–Chingual fault and finally followed by the reverse dextral Sub-Andean fault zone. While the Ecuadorian margin and Andes is affected by ENE–WSW shortening, the easternmost Manabí Basin located in between the Cordillera Costanera and the Cordillera Occidental of the Andes, underwent moderate ENE–WSW extension and constitutes an active fore-arc basin of the Nazca plate subduction. The integration of the GPS and seismic data evidences that highest rates of deformation and the highest tectonic hazards in Ecuador are linked: to the subduction zone located in the coastal area; to the Pallatanga transfer fault; and to the Eastern Andes Sub-Andean faults.

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