SciELO - Scientific Electronic Library Online

 
vol.60 número4Cargas subcorticales en el antepaís andino y la planicie pampeana: evidencias estratigráficas, topográficas y geofísicasConvergencia en el margen occidental de América del Sur durante el Cenozoico: subducción de las placas de Nazca, Farallón y Aluk índice de autoresíndice de materiabúsqueda de artículos
Home Pagelista alfabética de revistas  

Servicios Personalizados

Articulo

Indicadores

  • No hay articulos citadosCitado por SciELO

Links relacionados

  • En proceso de indezaciónCitado por Google
  • No hay articulos similaresSimilares en SciELO
  • En proceso de indezaciónSimilares en Google

Bookmark


Revista de la Asociación Geológica Argentina

versión On-line ISSN 1851-8249

Resumen

ALVARADO, P.; CASTRO DE MACHUCA, B.  y  BECK, S.. Comparative seismic and petrographic crustal study between the Western and Eastern Sierras Pampeanas region (31°S). Rev. Asoc. Geol. Argent. [online]. 2005, vol.60, n.4, pp. 787-796. ISSN 1851-8249.

The ancient Sierras Pampeanas in the central west part of Argentina are a seismically active region in the back-arc of the Andes. Their crystalline basement cored uplifts extend up to 800 km east of the oceanic trench over the flat subduction segment of the Nazca plate. Approximately 40 felt crustal earthquakes, are reported per year for this region. Historic and modern seismicity indicates that the Western Sierras Pampeanas (WSP) have more crustal earthquakes of greater-size than the Eastern Sierras Pampeanas (ESP). Remarkable changes in composition and structure also characterize the WSP and ESP basements. We have quantitatively compared both regions using seismological constrains. A recent regional study of moderate earthquakes shows reverse and thrust focal mechanisms occurring at depths down to 25 km in the WSP. In contrast, the ESP have reverse and strike-slip focal mechanisms of shallower depths (< 10 km). A seismic velocity structure of Vp 6.4 km/s, Vp/Vs ~1.80, and thickness 50 km, best represents the WSP crust. The ESP crust is characterized by Vp 6.0 km/s, Vp/Vs < 1.70, and thickness 30 km. These seismological determinations correlate with the interpretation of a different origin for the western and eastern terranes. The WSP show seismic properties indicative of a more mafic-ultramafic thick crust consistent with an oceanic island-arc and back-arc formation. The ESP show crustal seismic properties consistent with a higher silica content and with a formation by the collision of a continental terrane.

Palabras llave : Sierras Pampeanas; Seismotectonics; Continental crust.

        · resumen en Español     · texto en Inglés     · pdf en Inglés