1] A new Global Positioning System (GPS)-derived velocity field for the Andes mountains (26°-36°S... more 1] A new Global Positioning System (GPS)-derived velocity field for the Andes mountains (26°-36°S) allows analysis of instantaneous partitioning between elastic and anelastic deformation at the orogen's opposing sides. Adding an ''Andes'' microplate to the traditional description of Nazca-South America plate convergence provides the kinematic framework for nearly complete explanation of the observed velocity field. The results suggest the oceanic Nazca boundary is fully locked while the continental backarc boundary creeps continuously at $4.5 mm/yr. The excellent fit of model to data (1.7 mm/yr RMS velocity misfit), and the relative aseismicity of the upper crust in the interior Andean region in comparison with its boundaries, supports the notion that the mountains are not currently accruing significant permanent strains. Additionally, the model implies permanent deformation is not accumulating throughout the backarc contractional wedge, but rather that the deformation is accommodated only within a narrow deformational zone in the backarc.
1] A new Global Positioning System (GPS)-derived velocity field for the Andes mountains (26°-36°S... more 1] A new Global Positioning System (GPS)-derived velocity field for the Andes mountains (26°-36°S) allows analysis of instantaneous partitioning between elastic and anelastic deformation at the orogen's opposing sides. Adding an ''Andes'' microplate to the traditional description of Nazca-South America plate convergence provides the kinematic framework for nearly complete explanation of the observed velocity field. The results suggest the oceanic Nazca boundary is fully locked while the continental backarc boundary creeps continuously at $4.5 mm/yr. The excellent fit of model to data (1.7 mm/yr RMS velocity misfit), and the relative aseismicity of the upper crust in the interior Andean region in comparison with its boundaries, supports the notion that the mountains are not currently accruing significant permanent strains. Additionally, the model implies permanent deformation is not accumulating throughout the backarc contractional wedge, but rather that the deformation is accommodated only within a narrow deformational zone in the backarc.
The convergence between the Nazca and South America tectonic plates generates a seismically activ... more The convergence between the Nazca and South America tectonic plates generates a seismically active backarc region near 31°S. Earthquake locations define the subhorizontal subducted oceanic Nazca plate at depths of 90–120 km. Another seismic region is located within the continental upper plate with events at depths <35 km. This seismicity is related to the Precordillera and Sierras Pampeanas and is responsible for the large earthquakes that have caused major human and economic losses in Argentina. South of 33°S, the intense shallow continental seismicity is more restricted to the main cordillera over a region where the subducted Nazca plate starts to incline more steeply, and there is an active volcanic arc. We operated a portable broad-band seismic network as part of the Chile–Argentina Geophysical Experiment (CHARGE) from 2000 December to 2002 May. We have studied crustal earthquakes that occurred in the back arc and under the main cordillera in the south-central Andes (29°S–36°S) recorded by the CHARGE network. We obtained the focal mechanisms and source depths for 27 (3.5 < Mw < 5.3) crustal earthquakes using a moment tensor inversion method. Our results indicate mainly reverse focal mechanism solutions in the region during the CHARGE recording period. 88 per cent of the earthquakes are located north of 33°S and at middle-to-lower crustal depths. The region around San Juan, located in the western Sierras Pampeanas, over the flat-slab segment is dominated by reverse and thrust fault-plane solutions located at an average source depth of 20 km. One moderate-sized earthquake (event 02-117) is very likely related to the northern part of the Precordillera and the Sierras Pampeanas terrane boundary. Another event located near Mendoza at a greater depth (∼26 km) (event 02-005) could also be associated with the same ancient suture. We found strike-slip focal mechanisms in the eastern Sierras Pampeanas and under the main cordillera with shallower focal depths of ∼5–7 km. Overall, the western part of the entire region is more seismically active than the eastern part. We postulate that this is related to the presence of different pre-Andean geological terranes. We also find evidence for different average crustal models for those terranes. Better-fitting synthetic seismograms result using a higher P-wave velocity, a smaller average S-wave velocity and a thicker crust for seismic ray paths travelling through the crust of the western Sierras Pampeanas (Vp= 6.2–6.4 km s−1, Vp/Vs > 1.80, th = 45–55 km) than those of the eastern Sierras Pampeanas (Vp= 6.0–6.2 km s−1, Vp/Vs < 1.70, th = 27–35 km). In addition, we observed an apparent distribution of reverse crustal earthquakes along the suture that connects those terranes. Finally, we estimated average P and T axes over the CHARGE period. The entire region showed P- and T-axis orientations of 275° and 90°, plunging 6° and 84°, respectively.
LA guía de los fundamentos para la dirección de proyectos (Guía del PMBOK) es una norma reconocid... more LA guía de los fundamentos para la dirección de proyectos (Guía del PMBOK) es una norma reconocida en la profesión de la dirección de proyectos. Por norma se hace referencia a un documento formal que describe normas, métodos, procesos y practicas establecidos. Al igual que en otras profesiones, como la abogacía, la medicina y las ciencias económicas, el conocimiento contenido en esta norma evoluciono a partir de las buenas prácticas reconocidas por profesionales dedicados a la dirección de proyectos, quienes contribuyeron a su desarrollo.
1] A new Global Positioning System (GPS)-derived velocity field for the Andes mountains (26°-36°S... more 1] A new Global Positioning System (GPS)-derived velocity field for the Andes mountains (26°-36°S) allows analysis of instantaneous partitioning between elastic and anelastic deformation at the orogen's opposing sides. Adding an ''Andes'' microplate to the traditional description of Nazca-South America plate convergence provides the kinematic framework for nearly complete explanation of the observed velocity field. The results suggest the oceanic Nazca boundary is fully locked while the continental backarc boundary creeps continuously at $4.5 mm/yr. The excellent fit of model to data (1.7 mm/yr RMS velocity misfit), and the relative aseismicity of the upper crust in the interior Andean region in comparison with its boundaries, supports the notion that the mountains are not currently accruing significant permanent strains. Additionally, the model implies permanent deformation is not accumulating throughout the backarc contractional wedge, but rather that the deformation is accommodated only within a narrow deformational zone in the backarc.
1] A new Global Positioning System (GPS)-derived velocity field for the Andes mountains (26°-36°S... more 1] A new Global Positioning System (GPS)-derived velocity field for the Andes mountains (26°-36°S) allows analysis of instantaneous partitioning between elastic and anelastic deformation at the orogen's opposing sides. Adding an ''Andes'' microplate to the traditional description of Nazca-South America plate convergence provides the kinematic framework for nearly complete explanation of the observed velocity field. The results suggest the oceanic Nazca boundary is fully locked while the continental backarc boundary creeps continuously at $4.5 mm/yr. The excellent fit of model to data (1.7 mm/yr RMS velocity misfit), and the relative aseismicity of the upper crust in the interior Andean region in comparison with its boundaries, supports the notion that the mountains are not currently accruing significant permanent strains. Additionally, the model implies permanent deformation is not accumulating throughout the backarc contractional wedge, but rather that the deformation is accommodated only within a narrow deformational zone in the backarc.
The convergence between the Nazca and South America tectonic plates generates a seismically activ... more The convergence between the Nazca and South America tectonic plates generates a seismically active backarc region near 31°S. Earthquake locations define the subhorizontal subducted oceanic Nazca plate at depths of 90–120 km. Another seismic region is located within the continental upper plate with events at depths <35 km. This seismicity is related to the Precordillera and Sierras Pampeanas and is responsible for the large earthquakes that have caused major human and economic losses in Argentina. South of 33°S, the intense shallow continental seismicity is more restricted to the main cordillera over a region where the subducted Nazca plate starts to incline more steeply, and there is an active volcanic arc. We operated a portable broad-band seismic network as part of the Chile–Argentina Geophysical Experiment (CHARGE) from 2000 December to 2002 May. We have studied crustal earthquakes that occurred in the back arc and under the main cordillera in the south-central Andes (29°S–36°S) recorded by the CHARGE network. We obtained the focal mechanisms and source depths for 27 (3.5 < Mw < 5.3) crustal earthquakes using a moment tensor inversion method. Our results indicate mainly reverse focal mechanism solutions in the region during the CHARGE recording period. 88 per cent of the earthquakes are located north of 33°S and at middle-to-lower crustal depths. The region around San Juan, located in the western Sierras Pampeanas, over the flat-slab segment is dominated by reverse and thrust fault-plane solutions located at an average source depth of 20 km. One moderate-sized earthquake (event 02-117) is very likely related to the northern part of the Precordillera and the Sierras Pampeanas terrane boundary. Another event located near Mendoza at a greater depth (∼26 km) (event 02-005) could also be associated with the same ancient suture. We found strike-slip focal mechanisms in the eastern Sierras Pampeanas and under the main cordillera with shallower focal depths of ∼5–7 km. Overall, the western part of the entire region is more seismically active than the eastern part. We postulate that this is related to the presence of different pre-Andean geological terranes. We also find evidence for different average crustal models for those terranes. Better-fitting synthetic seismograms result using a higher P-wave velocity, a smaller average S-wave velocity and a thicker crust for seismic ray paths travelling through the crust of the western Sierras Pampeanas (Vp= 6.2–6.4 km s−1, Vp/Vs > 1.80, th = 45–55 km) than those of the eastern Sierras Pampeanas (Vp= 6.0–6.2 km s−1, Vp/Vs < 1.70, th = 27–35 km). In addition, we observed an apparent distribution of reverse crustal earthquakes along the suture that connects those terranes. Finally, we estimated average P and T axes over the CHARGE period. The entire region showed P- and T-axis orientations of 275° and 90°, plunging 6° and 84°, respectively.
LA guía de los fundamentos para la dirección de proyectos (Guía del PMBOK) es una norma reconocid... more LA guía de los fundamentos para la dirección de proyectos (Guía del PMBOK) es una norma reconocida en la profesión de la dirección de proyectos. Por norma se hace referencia a un documento formal que describe normas, métodos, procesos y practicas establecidos. Al igual que en otras profesiones, como la abogacía, la medicina y las ciencias económicas, el conocimiento contenido en esta norma evoluciono a partir de las buenas prácticas reconocidas por profesionales dedicados a la dirección de proyectos, quienes contribuyeron a su desarrollo.
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