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Una visión global del límite entre la litosfera y la astenosfera
Catherine A Rychert1, Peter M Shearer
1Institute of Geophysics and Planetary Physics, Scripps Institution of Oceanography, University of California, San Diego, 9500 Gilman Drive, M/C 0225, La Jolla, CA 92093, USA. crychert@ucsd.edu
Science (New York, N.Y.)
|April 25, 2009
Resumen
El límite entre la litosfera y la astenosfera.
Área de la Ciencia:
- La geofísica es la geofísica.
- Sismología Sismología Sismología.
- La tectónica de placas es la tectónica de placas.
Sus antecedentes:
- El límite entre la litosfera y la astenosfera es crucial para comprender la tectónica de placas.
- Su profundidad precisa y los mecanismos físicos que la definen siguen siendo poco conocidos.
- Los modelos existentes carecen de una resolución detallada en diversos entornos tectónicos.
Objetivo del estudio:
- Para obtener imágenes precisas del límite litosfera-astenosfera utilizando datos sísmicos.
- Para investigar cómo la profundidad y las características de la frontera varían con el entorno tectónico.
- Para determinar las propiedades físicas que definen esta importante interfaz geológica.
Principales métodos:
- Análisis de 15 años de datos sísmicos globales.
- Utilizando las fases sísmicas convertidas P-a-S (Ps) para la obtención de imágenes.
- Correlación de la profundidad de la interfaz sísmica con distintas configuraciones tectónicas (cratónicas, alteradas, oceánicas).
Principales resultados:
- Se obtuvo una imagen de una interfaz a diferentes profundidades: 95 km (escudos precámbricos), 81 km (regiones alteradas tectónicamente) y 70 km (islas oceánicas).
- Las observaciones de alta frecuencia Ps indican una aguda discontinuidad, no sólo un gradiente térmico.
- La interfaz de imágenes se correlaciona fuertemente con el entorno tectónico.
Conclusiones:
- La interfaz de imagen probablemente representa el límite litosfera-astenosfera en las regiones oceánicas y tectónicamente alteradas.
- En las regiones cratónicas, esta interfaz puede representar un límite diferente, con el verdadero límite litosfera-astenosfera potencialmente mucho más profundo.
- La naturaleza aguda del límite sugiere que está controlado por cambios de composición, fusión o anisotropía, en lugar de solo temperatura.
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