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Desarrollo de la estructura anisotrópica en el manto inferior de la Tierra por convección en estado sólido
Allen K McNamara1, Peter E van Keken, Shun-Ichiro Karato
1Department of Geological Sciences, University of Michigan, Ann Arbor, Michigan 48109-1063, USA. mcnamar@umich.edu
Nature
|March 22, 2002
Resumen
Las placas tectónicas subducidas que chocan con el límite núcleo-manto causan una fuerte anisotropía sísmica en el manto inferior de la Tierra. Esta deformación alinea los minerales, creando parches anisotrópicos observables, particularmente en la región circundante del Pacífico.
Área de la Ciencia:
- La geofísica es la geofísica.
- Física mineral Física de los minerales
- Sismología Sismología Sismología.
Sus antecedentes:
- Las observaciones sísmicas muestran parches altamente anisotrópicos en la base del manto inferior de la Tierra, en contraste con el manto masivo en gran medida isotrópico.
- Se supone que estas regiones anisotrópicas se originan a partir de la subducción pasada o el flujo ascendente del manto, pero la causa de la anisotropía sigue sin estar clara.
- Los mecanismos propuestos incluyen la orientación preferida por forma (SPO) de materiales heterogéneos o la orientación preferida por celosía (LPO) de material homogéneo, lo que implica diferentes procesos geodinámicos.
Objetivo del estudio:
- Para investigar las implicaciones geodinámicas de diferentes mecanismos de anisotropía en el manto inferior.
- Determinar si la deformación de gran esfuerzo de losas subducidas puede explicar la anisotropía sísmica observada.
- Para modelar el desarrollo del tejido mineral y su contribución a la anisotropía sísmica.
Principales métodos:
- Modelado numérico que incorpora la física mineral de la elasticidad.
- Modelado del desarrollo de la orientación preferida por celosía (LPO) a través de la deformación en estado sólido.
- Simulando la colisión de losas subducidas con el límite núcleo-manto.
Principales resultados:
- El estudio demuestra que la deformación de la losa en el manto inferior profundo puede generar una fuerte anisotropía sísmica.
- El modelo desarrollado, basado en material químicamente homogéneo del manto, muestra una anisotropía que surge de la deformación de gran tensión a altas tensiones.
- Este mecanismo explica efectivamente la anisotropía observada en la región circundante del Pacífico.
Conclusiones:
- La deformación en estado sólido del material químicamente homogéneo del manto, específicamente losas subducidas que chocan con el límite núcleo-manto, es una causa viable de anisotropía sísmica del manto inferior.
- La orientación preferida por el enrejado (LPO) debido a la deformación por gran esfuerzo a altas tensiones es el mecanismo dominante para generar una fuerte anisotropía en estas regiones.
- Los hallazgos concilian las observaciones sismológicas con los procesos geodinámicos que ocurren en la base del manto de la Tierra.
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