| Revista: | Revista brasileira de geofisica |
| Base de datos: | PERIÓDICA |
| Número de sistema: | 000279634 |
| ISSN: | 0102-261X |
| Autores: | Miranda, S1 |
| Instituciones: | 1Universidad Nacional de San Juan, Facultad de Ciencias Exactas, San Juan, Bahía Blanca. Argentina |
| Año: | 2000 |
| Periodo: | May-Ago |
| Volumen: | 18 |
| Número: | 2 |
| Paginación: | 107-116 |
| País: | Brasil |
| Idioma: | Inglés |
| Tipo de documento: | Artículo |
| Enfoque: | Experimental, analítico |
| Resumen en inglés | Up to date, three gravity models for the Andean section at 32° south latitude have been published. Two of them did not have seismic reflection/refraction data to constrain the subsurface geometry. The other one included seismic data to fit thicknesses and determined density contrasts using velocity-density curves. Furthermore, all previous models assumed a homogeneous mantle. In this paper a new gravity model is computed for a two-layer crust of the Andean section at the 32° south latitude. It involves new seismic depths for the Andean foreland, recent worldwide velocity-density relationships and a simple model of the subducting slab. The shape of the Nazca plate is defined from available contour maps of the Wadati-Benioff zone of western South America. The slab density contrast with respect to the surrounding mantle is estimated to be +1.6% (3.5-5.5% velocity anomaly), which reproduces the long-wavelength gravity anomaly. The modelled crustal structure is analyzed taking into account interpretations derived from seismic data. Crustal thicknesses vary from about 50 km in the Sierras Pampeanas to 71 km in the Andean belt. According to this model, most of the thickening takes place in the upper crustal layer, in the region between the Precordillera and Pampean Ranges. These results agree with recent seismological data. A Cenozoic lower crust shortening of 146 km to an initial crust 40 km thick is calculated from the computed crustal roots. This estimate of shortening is within 10% of previous calculations from gravity models. Also, i |
| Disciplinas: | Geociencias |
| Palabras clave: | Geofísica, Sismología y vulcanología, Campo de gravedad, Andes, Modelos gravimétricos, Manto superior, Placa de Nazca |
| Keyword: | Earth sciences, Geophysics, Seismology and volcanology, Gravity field, Andes, Upper mantle, Nazca plate |
| Texto completo: | Texto completo (Ver HTML) |
