Recurrence of megathrust events: Impact on hazard and risk in South America

2021 ◽  
Author(s):  
Jochen Woessner ◽  
Jessica Velasquez ◽  
Marleen Nyst ◽  
Delphine Fitzenz ◽  
Laura Eads
Keyword(s):  
Risk Management ◽  
South America ◽  
Seismic Hazard ◽  
Disaster Risk ◽  
South American ◽  
The South ◽  
South American Plate ◽  
Megathrust Earthquakes ◽  
Hazard And Risk ◽  
The Impact

<p>Megathrust earthquakes along the South American subduction zone where the Nazca plate slips below the South American plate rapidly subducts below the South American plate contribute significantly to the seismic hazard in Chile, Peru, Ecuador and Colombia. Estimating recurrence of the megathrust events is of prime interest not only for securing effective counter measures for engineering purposes, but also for assessing seismic hazard and risk for appropriate disaster risk management solutions in the insurance sector.</p><p>We present an evaluation and interpretation of recent research on the recurrence of megathrust earthquakes along the South America subduction zone. The modelling approach is conceptually founded in the asperity model and in this spirit evidence for documented earthquakes is assembled. We utilize time-independent and time-dependent recurrence models to understand the range and likelihood of recurrence times given the incomplete picture of the seismic history and the impact from uncertain event dates based on paleo-seismic / paleo-tsunami studies. In addition, we illustrate the sensitivity of recurrence rates for the largest earthquakes due to assumptions on seismic coupling and the size of potential ruptures.</p><p>Downstream from the recurrence rate analysis, the results are used to estimate the impact of the subduction interface model seismicity on a select set of exposure subject to earthquake shaking due to those events. These examples highlight the potential range of seismic hazard and risk and set the basis to further constrain disaster risk management solutions. </p>

scholarly journals Impact of enriched analyses on regional numerical forecasts over southeastern South America during SALLJEX

2014 ◽  
Vol 29 (3) ◽  
pp. 315-330
Author(s):  
Yanina García Skabar ◽  
Matilde Nicolini
Keyword(s):  
Data Assimilation ◽  
South America ◽  
Atmospheric Modeling ◽  
South American ◽  
The South ◽  
Low Level ◽  
Positive Effects ◽  
Accumulated Rainfall ◽  
Low Level Jet ◽  
The Impact

During the warm season 2002-2003, the South American Low-Level Jet Experiment (SALLJEX) was carried out in southeastern South America. Taking advantage of the unique database collected in the region, a set of analyses is generated for the SALLJEX period assimilating all available data. The spatial and temporal resolution of this new set of analyses is higher than that of analyses available up to present for southeastern South America. The aim of this paper is to determine the impact of assimilating data into initial fields on mesoscale forecasts in the region, using the Brazilian Regional Atmospheric Modeling System (BRAMS) with particular emphasis on the South American Low-Level Jet (SALLJ) structure and on rainfall forecasts. For most variables, using analyses with data assimilated as initial fields has positive effects on short term forecast. Such effect is greater in wind variables, but not significant in forecasts longer than 24 hours. In particular, data assimilation does not improve forecasts of 24-hour accumulated rainfall, but it has slight positive effects on accumulated rainfall between 6 and 12 forecast hours. As the main focus is on the representation of the SALLJ, the effect of data assimilation in its forecast was explored. Results show that SALLJ is fairly predictable however assimilating additional observation data has small impact on the forecast of SALLJ timing and intensity. The strength of the SALLJ is underestimated independently of data assimilation. However, Root mean square error (RMSE) and BIAS values reveal the positive effect of data assimilation up to 18-hours forecasts with a greater impact near higher topography.

scholarly journals The impact of the subtropical South Atlantic SST on South American precipitation

2008 ◽  
Vol 26 (11) ◽  
pp. 3457-3476 ◽  
Author(s):  
A. S. Taschetto ◽  
I. Wainer
Keyword(s):  
South America ◽  
Southern Oscillation ◽  
South Atlantic ◽  
Empirical Orthogonal Functions ◽  
Convergence Zone ◽  
South American ◽  
The South ◽  
Inter Tropical Convergence Zone ◽  
The Impact ◽  
Sst Anomalies

Abstract. The Community Climate Model (CCM3) from the National Center for Atmospheric Research (NCAR) is used to investigate the effect of the South Atlantic sea surface temperature (SST) anomalies on interannual to decadal variability of South American precipitation. Two ensembles composed of multidecadal simulations forced with monthly SST data from the Hadley Centre for the period 1949 to 2001 are analysed. A statistical treatment based on signal-to-noise ratio and Empirical Orthogonal Functions (EOF) is applied to the ensembles in order to reduce the internal variability among the integrations. The ensemble treatment shows a spatial and temporal dependence of reproducibility. High degree of reproducibility is found in the tropics while the extratropics is apparently less reproducible. Austral autumn (MAM) and spring (SON) precipitation appears to be more reproducible over the South America-South Atlantic region than the summer (DJF) and winter (JJA) rainfall. While the Inter-tropical Convergence Zone (ITCZ) region is dominated by external variance, the South Atlantic Convergence Zone (SACZ) over South America is predominantly determined by internal variance, which makes it a difficult phenomenon to predict. Alternatively, the SACZ over western South Atlantic appears to be more sensitive to the subtropical SST anomalies than over the continent. An attempt is made to separate the atmospheric response forced by the South Atlantic SST anomalies from that associated with the El Niño – Southern Oscillation (ENSO). Results show that both the South Atlantic and Pacific SSTs modulate the intensity and position of the SACZ during DJF. Particularly, the subtropical South Atlantic SSTs are more important than ENSO in determining the position of the SACZ over the southeast Brazilian coast during DJF. On the other hand, the ENSO signal seems to influence the intensity of the SACZ not only in DJF but especially its oceanic branch during MAM. Both local and remote influences, however, are confounded by the large internal variance in the region. During MAM and JJA, the South Atlantic SST anomalies affect the magnitude and the meridional displacement of the ITCZ. In JJA, the ENSO has relatively little influence on the interannual variability of the simulated rainfall. During SON, however, the ENSO seems to counteract the effect of the subtropical South Atlantic SST variations on convection over South America.

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

<p>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-Chocó 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 (Agustín 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.</p>

scholarly journals The impact of the South-American plate motion and the Nazca Ridge subduction on the flat subduction below South Peru

2002 ◽  
Vol 29 (14) ◽  
pp. 35-1-35-4 ◽  
Author(s):  
Jeroen van Hunen ◽  
Arie P. van den Berg ◽  
Nico J. Vlaar
Keyword(s):  
Plate Motion ◽  
South American ◽  
The South ◽  
South American Plate ◽  
Ridge Subduction ◽  
Nazca Ridge ◽  
The Impact

scholarly journals Subduction initiation in the Scotia Sea region and opening of the Drake Passage: when and why?

2021 ◽  
Author(s):  
Suzanna van de Lagemaat ◽  
Merel Swart ◽  
Bram Vaes ◽  
Martha Kosters ◽  
Lydian Boschman ◽  
...  
Keyword(s):  
South America ◽  
Subduction Zone ◽  
Continental Crust ◽  
Drake Passage ◽  
Plate Motion ◽  
South American ◽  
The South ◽  
South American Plate ◽  
Scotia Sea ◽  
The Antarctic

<p>During evolution of the South Sandwich subduction zone, which has consumed South American plate oceanic lithosphere, somehow continental crust of both the South American and Antarctic plates have become incorporated into its upper plate. Continental fragments of both plates are currently separated by small oceanic basins in the upper plate above the South Sandwich subduction zone, in the Scotia Sea region, but how fragments of both continents became incorporated in the same upper plate remains enigmatic. Here we present an updated kinematic reconstruction of the Scotia Sea region using the latest published marine magnetic anomaly constraints, and place this in a South America-Africa-Antarctica plate circuit in which we take intracontinental deformation into account. We show that a change in fracture zone orientation in the Weddell Sea requires that previously inferred initiation of subduction of South American oceanic crust of the northern Weddell below the eastern margin of South Orkney Islands continental crust, then still attached to the Antarctic Peninsula, already occurred around 80 Ma. We propose that subsequently, between ~71-50 Ma, the trench propagated northwards into South America by delamination of South American lithosphere: this resulted in the transfer of delaminated South American continental crust to the overriding plate of the South Sandwich subduction zone. We show continental delamination may have been facilitated by absolute southward motion of South America that was resisted by South Sandwich slab dragging. Pre-drift extension preceding the oceanic Scotia Sea basins led around 50 Ma to opening of the Drake Passage, preconditioning the southern ocean for the Antarctic Circumpolar Current. This 50 Ma extension was concurrent with a strong change in absolute plate motion of the South American Plate that changed from S to WNW, leading to upper plate retreat relative to the more or less mantle stationary South Sandwich Trench that did not partake in the absolute plate motion change. While subduction continued, this mantle-stationary trench setting lasted until ~30 Ma, after which rollback started to contribute to back-arc extension. We find that roll-back and upper plate retreat have contributed more or less equally to the total amount of ~2000 km of extension accommodated in the Scotia Sea basins. We highlight that viewing tectonic motions in a context of absolute plate motion is key for identifying slab motion (e.g. rollback, trench-parallel slab dragging) and consequently mantle-forcing of geological processes.</p>

The Tectonic Framework of South America

2007 ◽  
Author(s):  
Antony R. Orme
Keyword(s):  
South America ◽  
Plate Tectonics ◽  
South American ◽  
Convergent Margins ◽  
The South ◽  
South American Plate ◽  
Passive Margins ◽  
Tectonic Framework ◽  
Oceanic Plates ◽  
The Many

Tectonism is the science of Earth movements and the rocks and structures involved therein. These movements build the structural framework that supports the stage on which surface processes, plants, animals and, most recently, people pursue their various roles under an atmospheric canopy. An appreciation of this tectonic framework is thus a desirable starting point for understanding the physical geography of South America, from its roots in the distant past through the many and varied changes that have shaped the landscapes visible today. Tectonic science recognizes that Earth’s lithosphere comprises rocks of varying density that mobilize as relatively rigid plates, some continental in origin, some oceanic, and some, like the South American plate, amalgams of both continental and oceanic rocks. These plates shift in response to deep-seated forces, such as convection in the upper mantle, and crustal forces involving push and pull mechanics between plates. Crustal motions, augmented by magmatism, erosion, and deposition, in turn generate complex three-dimensional patterns. Although plate architecture has changed over geologic time, Earth’s lithosphere is presently organized into seven major plates, including the South American plate, and numerous smaller plates and slivers. The crustal mobility implicit in plate tectonics often focuses more attention on plate margins than on plate interiors. In this respect, it is usual to distinguish between passive margins, where plates are rifting and diverging, and active margins, where plates are either converging or shearing laterally alongside one another. At passive or divergent margins, such as the present eastern margin of the South American plate, severe crustal deformation is rare but crustal flexuring (epeirogeny), faulting, and volcanism occur as plates shift away from spreading centers, such as the Mid-Atlantic Ridge, where new crust is forming. Despite this lack of severe postrift deformation, however, passive margins commonly involve the separation of highly deformed rocks and structures that were involved in the earlier assembly of continental plates, as shown by similar structural legacies in the facing continental margins of eastern South America and western Africa. At active convergent margins, mountain building (orogeny) commonly results from subduction of oceanic plates, collision of continental plates, or accretion of displaced terranes.

Ocean Coasts and Continental Shelves

2007 ◽  
Author(s):  
José Araya-Vergara
Keyword(s):  
South America ◽  
Atlantic Coast ◽  
South American ◽  
The South ◽  
South American Plate ◽  
The Pacific ◽  
Analytical Perspective ◽  
Oceanic Plates ◽  
The 1960S ◽  
The Tropics

Suess (1900) provided the first scientific treatment of the South American coast from a tectonic perspective when he distinguished between the Atlantic and Pacific structural styles on opposite sides of the continent. Inman and Nordstrom (1971) later complemented this approach by relating these styles to the concepts of plate tectonics that had emerged during the 1960s. Useful keys to understanding South American coastal processes and sediment supplies were then offered by Davies (1977) and Potter (1994), respectively, while regional accounts of South American coastal landforms were made by specialists in books edited by Bird and Schwartz (1985) and Schwartz (2005). Clapperton (1993) reviewed Quaternary coastal morphogenesis. Coastal sites of scientific importance and historical coastline changes were discussed by Bird and Koike (1981) and Bird (1985). This chapter focuses on the principal factors involved in coastal evolution and morphogenesis, describes key regional landforms, and proposes a new analytical perspective for South America’s coasts by introducing a hierarchical system within coastal groups. The main coastline of South America is approximately 31,100 km long, of which 10,400 km face the Pacific Ocean, 16,700 the open Atlantic Ocean, and the remaining 4,000 km the more sheltered Caribbean Sea. Of the total length, approximately two-thirds lie within the tropics, ensuring that physical and ecological responses to ocean-atmosphere circulation systems involving the Intertropical Convergence Zone dominate these coasts. The remaining one third of the coast beyond the tropics is dominated during part or all of the year by temperate westerly conditions, which become increasingly cool and stormy toward the continent’s southern tip. The origins of the present coast reflect the tectonic forces that have affected the South American plate over the past 200 million years, augmented by relative sea-level changes associated with changing global (eustatic) ocean volume and regional (isostatic) crustal adjustments. The Atlantic coast of South America owes its broad outline to the separation of the continent from neighboring parts of Gondwana that began more than 200 Ma (million years ago). The Pacific and Caribbean coasts have a more complex history, related to the progressive interaction of the westwardmoving South American plate with four oceanic plates with which it has come into contact).

A Hazard and Risk Management System for Large Rock Slope Hazards Affecting Pipelines in Mountainous Terrain

2002 ◽  
Author(s):  
Michael Porter ◽  
Alex Baumgard ◽  
K. Wayne Savigny
Keyword(s):  
Risk Management ◽  
Rock Slope ◽  
Management Program ◽  
South American ◽  
Mountainous Terrain ◽  
Hazard Exposure ◽  
Access Road ◽  
Hazard And Risk ◽  
The Right ◽  
Hazard Rating

Pipelines and other linear facilities that traverse mountainous terrain may be subject to rock fall and rock slide hazards. A system is required to determine which sites pose the greatest hazard to the facility. Once sites are ranked according to hazard exposure, a risk management program involving inspection, monitoring, contingency planning and/or mitigation can be implemented in a systematic and defensible manner. A hazard rating methodology was developed to identify and characterize rock slope hazards above a South American Concentrate Pipeline, and to provide a relative ranking of hazard exposure for the pipeline, an access road and operational personnel. The rating methodology incorporates the geometry of the right-of-way, estimated pipe depth, staff and vehicle occupancy time, failure mechanism and magnitude, and the annual probability of hazard occurrence. This information is used in a risk-based framework to assign relative hazard ratings within rock slope sections of relatively uniform hazard exposure. This paper outlines a general framework for natural hazard and risk management along linear facilities, describes the rock slope hazard rating methodology, and illustrates how the system was applied along a South American Concentrate Pipeline.

scholarly journals Problems and prospects of MERCOSUR as a civilizational political project of South America

2020 ◽  
pp. 1-8
Author(s):  
Mikhail Valer'evich Gorbachev
Keyword(s):  
South America ◽  
The Political ◽  
South American ◽  
Core State ◽  
The South ◽  
Project Approach ◽  
Political Project ◽  
Key Participants ◽  
Further Development

  This article discusses the political projects of civilizational level, which are designed and implemented in South America. The author examines MERCOSUR as the largest regional civilizational political project, its sociocultural foundation and institutional superstructure; functionality of the “core state” in formation and maintenance of the South American civilizational political project; problems of development and future implementation. The article reveals conflict potential of MERCOSUR, as well as sociocultural capabilities for its overcoming by the “core state” of the project. The research was conducted via application of civilizational-project methodology of interpretation of policy, which is based on methodological synthesis of the principles of project approach with provisions of the theory of civilizations. The author was able to determine the value grounds of MERCOSUR, which comprise its sociocultural foundation; identify the countries competing for status of the “core state” within the framework of this project. The nature of commonality between the key participants of the projects is identified. Problems and prospect of further development of MERCOSUR civilizational projects are defined.  

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