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.

scholarly journals Measuring the seismic risk along the Nazca–South American subduction front: Shannon entropy and mutability

2020 ◽  
Vol 20 (11) ◽  
pp. 2943-2960
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 greater than or equal to 3.0 is set up and then characterized by Shannon entropy and mutability. These methods show a correlation after a major earthquake in what is known as the aftershock regime but show independence otherwise. Exponential adjustments to these parameters reveal that mutability offers a wider range for the parameters to characterize 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 of 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 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.

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.

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.

Metamorphic evolution of Raspas complex (Ecuador) and its relation with a J-K belt of melanges in NW of the South American plate.

2020 ◽  
Author(s):  
Mayda Arrieta-Prieto ◽  
Carlos Zuluaga-Castrillón ◽  
Oscar Castellanos-Alarcón ◽  
Carlos Ríos-Reyes
Keyword(s):  
High Pressure ◽  
Subduction Zones ◽  
Mineral Chemistry ◽  
White Mica ◽  
Petrographic Analysis ◽  
South American ◽  
The South ◽  
South American Plate ◽  
Subduction Channel ◽  
Southern Ecuador

&lt;p&gt;High-pressure complexes along the Earth's surface provide evidence of the processes involved in both the crystallization of rocks in the subduction channel and its exhumation. Such processes are key to understand the dynamics and evolution of subduction zones and to try to reconstruct P-T trajectories for these complexes.&lt;/p&gt;&lt;p&gt;Previous studies on the Raspas complex (southern Ecuador) agree to state that it is composed of metamorphic rocks, mainly blueschists and eclogites, containing the mineral assemblage: glaucophane + garnet + epidote + omphacite + white mica + rutile &amp;#177; quartz &amp;#177; apatite &amp;#177; pyrite &amp;#177; calcite; which stabilized in metamorphic conditions of high pressure and low temperature. Additionally, the Raspas Complex has been genetically related to accretion and subduction processes of seamounts, which occurred in South America during the Late Jurassic - Early Cretaceous interval; and the exhumation of the complex was related to subduction channels. However, the evidence presented in the existing literature makes little emphasis on the reconstruction of thermobarometric models for the rocks of this complex.&lt;/p&gt;&lt;p&gt;By combining petrographic observations, whole-rock chemistry, and mineral chemistry in this work; it was possible to determine that pressure values of 10 &amp;#177; 3 Kbar and temperature values of 630 &amp;#177; 30 &amp;#176; C, (obtained by simulations with THERMOCALC&amp;#174;) correspond to an event of retrograde metamorphism, suffered by the complex during its exhumation. This theory is complemented by the specific textures (that suggest this retrograde process) observed during petrographic analysis, such as amphibole replacing pyroxene, garnet chloritization, plagioclase crystallization and rutile replacement by titanite.&lt;/p&gt;&lt;p&gt;The results obtained, together with the thermobarometry data published for the Arqu&amp;#237;a complex in Colombia, allow us to establish a P-T trajectory, that may suggest a genetic relationship between these two complexes as a result of the tectonic processes associated with an active subduction margin that affected the NW margin of the South American plate at the end of the Jurassic.&lt;/p&gt;&lt;p&gt;&amp;#160;&lt;/p&gt;

Geodynamic study of the north of the Andes block (Colombia, Panama, Ecuador and Venezuela) through gnss-gps: models of displacements, models of deformation and definition of local and regional geodynamic structures.

2020 ◽  
Author(s):  
Berrocoso Manuel ◽  
Del Valle Arroyo Pablo Emilio ◽  
Colorado Jaramillo David Julián ◽  
Gárate Jorge ◽  
Fernández-Ros Alberto ◽  
...  
Keyword(s):  
South America ◽  
Seismic Activity ◽  
Great Part ◽  
Velocity Model ◽  
South American ◽  
The South ◽  
South American Plate ◽  
Northern Andes ◽  
Velocity Models ◽  
The North

&lt;p&gt;The northwest of South America is conformed by the territories of Ecuador, Colombia and Venezuela. Great part of these territories make up the Northern Andes Block (BAN). The tectonic and volcanic activity in the northwest of South America is directly related to the interaction of the South American plate, and the Nazca and Caribbean plates, with the Maracaibo and Panama-Choc&amp;#243; micro plates. The high seismic activity and the high magnitude of the recorded earthquakes make any study necessary to define this complex geodynamic region more precisely. This work presents the velocity models obtained through GNSS-GPS observations obtained in public continuous monitoring stations in the region. The observations of the Magna-eco network (Agust&amp;#237;n Codazzi Geographic Institute) are integrated with models already obtained by other authors from the observations of the GEORED network (Colombian Geological Service). The observations have been processed using Bernese software v.52 using the PPP technique; obtaining topocentric time series. To obtain the speeds, a process of filtering and adjustment of the topocentric series has been carried out. Based on this velocity model, regional structures have been defined within the Northern Andes Block through a differentiation process based on the corresponding speeds of the South American, Nazca and Caribbean tectonic plates. Local geodynamic structures within the BAN itself have been established through cluster analysis based on both the direction and the magnitude of each of the vectors obtained. Finally, these structures have been correlated with the most significant geodynamic elements (fractures, faults, subduction processes, etc.) and with the associated seismic activity.&lt;/p&gt;

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;

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