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Detección sísmica de la litosfera doblada y subducida en el límite núcleo-manto
Alexander R Hutko1, Thorne Lay, Edward J Garnero
1Earth Sciences Department, University of California Santa Cruz, 1156 High Street, Santa Cruz, California 95064, USA. ahutko@pmc.ucsc.edu
Nature
|May 20, 2006
Resumen
La subducción de losas oceánicas alcanza el manto inferior de la Tierra, creando un paso en la discontinuidad sísmica D'. Este paso se explica por el material de la losa plegada que altera el límite de la fase post-perovskita cerca del límite entre el núcleo y el manto.
Área de la Ciencia:
- La geofísica es la geofísica.
- Sismología Sismología Sismología.
- Física de los minerales Física de los minerales
Sus antecedentes:
- Las losas oceánicas descendentes penetran en el manto inferior de la Tierra, alcanzando la región D''.
- La región D'' exhibe altas velocidades sísmicas y una discontinuidad, potencialmente vinculada a un cambio de fase de perovskita de silicato de magnesio.
- El destino final y la expresión sísmica de losas subducidas en el manto más bajo siguen siendo objeto de debate.
Objetivo del estudio:
- Para obtener imágenes de la región D'' debajo de la placa de Cocos.
- Para investigar la estructura de la velocidad sísmica y las discontinuidades en el límite núcleo-manto.
- Para entender la influencia de losas subducidas en las propiedades sísmicas de la región D''.
Principales métodos:
- Migración de Kirchhoff de las ondas de corte polarizadas horizontalmente.
- Tomografía sísmica para inferir la estructura del manto.
- Análisis de las discontinuidades de velocidad sísmica.
Principales resultados:
- Se observó un paso vertical de 100 km en la discontinuidad de velocidad de cizallamiento D' debajo de la placa de Cocos.
- Este paso se produjo lateralmente en menos de 100 km.
- Se detectaron bajas velocidades localizadas en el borde del material de la losa.
Conclusiones:
- El paso observado se atribuye al plegado y apilamiento de una losa subducida en frío en el límite núcleo-manto.
- Este plegamiento de la losa eleva el límite de la fase posterior a la perovskita debido a una reducción significativa de la temperatura lateral.
- Las bajas velocidades localizadas sugieren que las subidas inducidas por la losa desplazan una capa térmica límite.
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