The NAZCA Plate

2013 ◽  
pp. 16-19
Author(s):  
L.D. Kulm ◽  
Leonidas Ocola
Keyword(s):  
Nazca Plate

Seismicity of the Earth 1900-2007, Nazca Plate and South America

2010 ◽  
Author(s):  
Susan Rhea ◽  
Gavin P. Hayes ◽  
Antonio H. Villaseñor ◽  
Kevin P. Furlong ◽  
Arthur C. Tarr ◽  
...  
Keyword(s):  
South America ◽  
Nazca Plate ◽  
The Earth

Ground-motion model for subduction earthquakes in northern South America

2021 ◽  
pp. 875529302110275
Author(s):  
Carlos A Arteta ◽  
Cesar A Pajaro ◽  
Vicente Mercado ◽  
Julián Montejo ◽  
Mónica Arcila ◽  
...  
Keyword(s):  
South America ◽  
Ground Motion ◽  
Ground Motions ◽  
Strong Motion ◽  
Motion Prediction ◽  
Depth Range ◽  
Ground Motion Prediction ◽  
Natural Period ◽  
Nazca Plate ◽  
Northern South America

Subduction ground motions in northern South America are about a factor of 2 smaller than the ground motions for similar events in other regions. Nevertheless, historical and recent large-interface and intermediate-depth slab earthquakes of moment magnitudes Mw = 7.8 (Ecuador, 2016) and 7.2 (Colombia, 2012) evidenced the vast potential damage that vulnerable populations close to earthquake epicenters could experience. This article proposes a new empirical ground-motion prediction model for subduction events in northern South America, a regionalization of the global AG2020 ground-motion prediction equations. An updated ground-motion database curated by the Colombian Geological Survey is employed. It comprises recordings from earthquakes associated with the subduction of the Nazca plate gathered by the National Strong Motion Network in Colombia and by the Institute of Geophysics at Escuela Politécnica Nacional in Ecuador. The regional terms of our model are estimated with 539 records from 60 subduction events in Colombia and Ecuador with epicenters in the range of −0.6° to 7.6°N and 75.5° to 79.6°W, with Mw≥4.5, hypocentral depth range of 4 ≤  Zhypo ≤ 210 km, for distances up to 350 km. The model includes forearc and backarc terms to account for larger attenuation at backarc sites for slab events and site categorization based on natural period. The proposed model corrects the median AG2020 global model to better account for the larger attenuation of local ground motions and includes a partially non-ergodic variance model.

scholarly journals Magnetotelluric study in the Los Lagos Region (Chile) to investigate volcano-tectonic processes in the Southern Andes

2021 ◽  
Vol 73 (1) ◽  
Author(s):  
Maria Jose Segovia ◽  
Daniel Diaz ◽  
Katarzyna Slezak ◽  
Felipe Zuñiga
Keyword(s):  
Electrical Resistivity ◽  
Three Dimensional ◽  
Phase Changes ◽  
Fault System ◽  
Electrical Anisotropy ◽  
Mountain Range ◽  
Southern Andes ◽  
Nazca Plate ◽  
First Results ◽  
Dimensional Parameters

AbstractTo analyze the process of subduction of the Nazca and South American plates in the area of the Southern Andes, and its relationship with the tectonic and volcanic regime of the place, magnetotelluric measurements were made through a transversal profile of the Chilean continental margin. The data-processing stage included the analysis of dimensional parameters, which as first results showed a three-dimensional environment for periods less than 1 s and two-dimensional for periods greater than 10 s. In addition, through the geomagnetic transfer function (tipper), the presence of structural electrical anisotropy was identified in the data. After the dimensional analysis, a deep electrical resistivity image was obtained by inverting a 2D and a 3D model. Surface conductive anomalies were obtained beneath the central depression related to the early dehydration of the slab and the serpentinization process of the mantle that coincides in location with a discontinuity in the electrical resistivity of a regional body that we identified as the Nazca plate. A shallow conductive body was located around the Calbuco volcano and was correlated with a magmatic chamber or reservoir which in turn appears to be connected to the Liquiñe Ofqui fault system and the Andean Transverse Fault system. In addition to the serpentinization process, when the oceanic crust reaches a depth of 80–100 km, the ascending fluids produced by the dehydration and phase changes of the minerals present in the oceanic plate produce basaltic melts in the wedge of the subcontinental mantle that give rise to an eclogitization process and this explains a large conductivity anomaly present beneath the main mountain range.

scholarly journals Mantle Melting and Magmatic Processes Under La Picada Stratovolcano (CSVZ, Chile)

2019 ◽  
Vol 60 (5) ◽  
pp. 907-944 ◽  
Author(s):  
Jacqueline Vander Auwera ◽  
Olivier Namur ◽  
Adeline Dutrieux ◽  
Camilla Maya Wilkinson ◽  
Morgan Ganerød ◽  
...  
Keyword(s):  
Fractional Crystallization ◽  
Geochemical Data ◽  
Upper Crust ◽  
Volcanic Zone ◽  
Nazca Plate ◽  
Southern Volcanic Zone ◽  
Magmatic Processes ◽  
Crystal Accumulation ◽  
Primary Magmas ◽  
Differentiation Trend

Abstract Where and how arc magmas are generated and differentiated are still debated and these questions are investigated in the context of part of the Andean arc (Chilean Southern Volcanic Zone) where the continental crust is thin. Results are presented for the La Picada stratovolcano (41°S) that belongs to the Central Southern Volcanic Zone (CSVZ) (38°S–41·5°S, Chile) which results from the subduction of the Nazca plate beneath the western margin of the South American continent. Forty-seven representative samples collected from different units of the volcano define a differentiation trend from basalt to basaltic andesite and dacite (50·9 to 65·6 wt % SiO2). This trend straddles the tholeiitic and calc-alkaline fields and displays a conspicuous compositional Daly Gap between 57·0 and 62·7 wt % SiO2. Interstitial, mostly dacitic, glass pockets extend the trend to 76·0 wt % SiO2. Mineral compositions and geochemical data indicate that differentiation from the basaltic parent magmas to the dacites occurred in the upper crust (∼0·2 GPa) with no sign of an intermediate fractionation stage in the lower crust. However, we have currently no precise constraint on the depth of differentiation from the primary magmas to the basaltic parent magmas. Stalling of the basaltic parent magmas in the upper crust could have been controlled by the occurrence of a major crustal discontinuity, by vapor saturation that induced volatile exsolution resulting in an increase of melt viscosity, or by both processes acting concomitantly. The observed Daly Gap thus results from upper crustal magmatic processes. Samples from both sides of the Daly Gap show contrasting textures: basalts and basaltic andesites, found as lavas, are rich in macrocrysts, whereas dacites, only observed in crosscutting dykes, are very poor in macrocrysts. Moreover, modelling of the fractional crystallization process indicates a total fractionation of 43% to reach the most evolved basaltic andesites. The Daly Gap is thus interpreted as resulting from critical crystallinity that was reached in the basaltic andesites within the main storage region, precluding eruption of more evolved lavas. Some interstitial dacitic melt was extracted from the crystal mush and emplaced as dykes, possibly connected to small dacitic domes, now eroded away. In addition to the overall differentiation trend, the basalts to basaltic andesites display variable MgO, Cr and Ni contents at a given SiO2. Crystal accumulation and high pressure fractionation fail to predict this geochemical variability which is interpreted as resulting from variable extents of fractional crystallization. Geothermobarometry using recalculated primary magmas indicates last equilibration at about 1·3–1·5 GPa and at a temperature higher than the anhydrous peridotite solidus, pointing to a potential role of decompression melting. However, because the basalts are enriched in slab components and H2O compared to N-MORB, wet melting is highly likely.

Differences in the rupture process for very deep earthquakes at the Peru-Brazil and Peru-Bolivia borders 

2021 ◽  
Author(s):  
Elisa Buforn ◽  
Carmen Pro ◽  
Hernando Tavera ◽  
Agustin Udias ◽  
Maurizio Mattesini
Keyword(s):  
Focal Depth ◽  
Vertical Plane ◽  
Rupture Process ◽  
The South ◽  
Nazca Plate ◽  
Deep Earthquakes ◽  
Pressure Axis ◽  
Rate Functions ◽  
The Moment ◽  
Epicentral Location

<p>We analyze the differences in the rupture process for twelve very deep earthquakes (h>500 km) at the Peruvian-Brazilian subduction zone. These earthquakes are produced by the contact between the Nazca and the South America Plates. We have estimated the focal mechanism from teleseismic waveforms, using the slip inversion over the rupture plane, testing rupture velocities ranging from 2.5 km/s to 4.5 km/s, and analyzing the slip distribution for each  rupture velocity. The selected 12 earthquakes have occurred in the period 1994- 2016, with magnitudes between 5.9 and 8.2 and focal depth 500- 700 km. They can be separated in two groups attending to their epicentral location. The first group is formed by 9 events located, in the Peruvian-Brazil border, with epicenters following a NNW-SSE alignment, parallel to the trench. Their focal mechanisms present solutions of normal faulting with planes oriented in NS direction, dipping about 45 degrees and with vertical pressure axis. The second group is formed by three earthquakes located to the south of the first group in northern Bolivia. Their mechanisms show dip-slip motion with a near vertical plane, oriented in NW-SE direction and the pressure axis dipping 45º to the NE. The moment rate functions correspond to single ruptures with time durations from 6s to 12s, with the exception of the large 1994 Bolivian earthquake (Mw = 8.2) which presents a complex and longer STF. The different mechanisms for the two groups of earthquakes confirm the different dip of the subducting Nazca plate at the two areas, with the steeper part at the southern one.  </p>

Slab tearing of the Nazca plate in the Central Andes and its interaction with the overriding plate

2021 ◽  
Author(s):  
Nipaporn (Nidnueng) Nakrong ◽  
Wim Spakman ◽  
Fangqin Chen ◽  
Gordon Lister
Keyword(s):  
Structural Geology ◽  
South America ◽  
Seismic Tomography ◽  
Strike Slip ◽  
Surface Structures ◽  
Nazca Plate ◽  
Tectonic Reconstruction ◽  
Subducting Plate ◽  
Slab Tearing ◽  
Subduction System

<p>Slab tearing in subducting plates is widely implicated in terms of the factors that control the evolution of the structural geology of the over-riding crust, here illustrated by interactions between the subducting Nazca plate and the overlying overthrust western continental margin of South America. We examine the different ways that structures above the bounding megathrusts are linked to the ripping and tearing of the subducting plate beneath, in particular focussed on the Andean orogeny at the Arica bend during the formation of the Bolivian orocline. We can create models for slab tearing by integrating seismotectonic analysis, seismic tomography, and morphotectonics. There are many features in the UU-P07 tomographic model that we cannot yet relate to the evolution of surface structure, for example, the gaps and tears beneath the Bolivian Orocline, or the separation of the detached slab we interpret as a paleo-segment of the Nazca plate, illustrating traces of an ancient subduction system. However, we can link the evolution of some surface structures to the growth of the giant kink of the Nazca slab that connects to the surface near the Arica bend. This may have driven strike-slip faulting with opposing sense-of-shear, northern south of the Bolivian Orocline. Megathrust rupture segments may be related to the polygonal kinked trace of the orogen, which is not at all a continuously curved arc. In this contribution, we relate the growth and accentuation of the Arica Bend to the evolution of the giant kink in the Nazca plate using a 4-D tectonic reconstruction.</p>

New terrestrial heat flow measurements on the Nazca Plate

1976 ◽  
Vol 29 (2) ◽  
pp. 243-254 ◽  
Author(s):  
Roger N. Anderson ◽  
Marcus G. Langseth ◽  
Victor Vacquier ◽  
Jean Francheteau
Keyword(s):  
Heat Flow ◽  
Flow Measurements ◽  
Nazca Plate ◽  
Terrestrial Heat Flow

scholarly journals Active Tectonics of the North Chilean Marine Forearc and Adjacent Oceanic Nazca Plate

Tectonics ◽  
2018 ◽  
Vol 37 (11) ◽  
pp. 4194-4211 ◽  
Author(s):  
Jacob Geersen ◽  
César R. Ranero ◽  
Ingo Klaucke ◽  
Jan H. Behrmann ◽  
Heidrun Kopp ◽  
...  
Keyword(s):  
Active Tectonics ◽  
Nazca Plate ◽  
The North
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