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Deformación del manto más bajo por anisotropía sísmica
Andy Nowacki1, James Wookey, J-Michael Kendall
1Department of Earth Sciences, University of Bristol, Wills Memorial Building, Queen's Road, Bristol, BS8 1RJ, UK. andy.nowacki@bristol.ac.uk
Nature
|October 29, 2010
Resumen
La anisotropía sísmica en la capa D′′ de la Tierra sugiere la deformación MgSiO(3) después de la perovskita. Nuevas mediciones revelan que son necesarios mecanismos complejos para explicar la división de las ondas sísmicas, lo que apunta al cizallamiento en (001) como una causa probable.
Área de la Ciencia:
- La geofísica es la geofísica.
- Sismología Sismología Sismología.
- Física mineral Física de los minerales
Sus antecedentes:
- El manto más bajo de la Tierra (D′′) exhibe una anisotropía sísmica significativa.
- Esta anisotropía es probablemente causada por la alineación de MgSiO3 post-perovskita (ppv), la fase mineral dominante.
- Las mediciones anteriores de anisotropía tenían un alcance limitado, lo que dificultaba la comprensión de los mecanismos de deformación de ppv.
Objetivo del estudio:
- Para investigar la anisotropía sísmica en la capa D′′ debajo de América del Norte y Central.
- Para distinguir entre los mecanismos candidatos de deslizamiento en MgSiO(3) -ppv.
- Mejorar la comprensión de los procesos de deformación en el límite núcleo-manto.
Principales métodos:
- Mediciones de la división de la onda de cizallamiento en la capa D′′ utilizando terremotos poco profundos y profundos.
- Adquisición de más de 700 mediciones en tres regiones con mayor cobertura azimutal.
- Prueba de varios mecanismos de deformación MgSiO(3)-ppv contra los datos sísmicos observados.
Principales resultados:
- El modelo de isotropía transversal vertical previamente asumido para D ′′ no está respaldado por los datos.
- Se requieren mecanismos de deformación más complejos para explicar la anisotropía sísmica observada.
- El cizallamiento en el plano (001) de MgSiO(3)-ppv es la explicación más consistente para la anisotropía observada.
Conclusiones:
- Los hallazgos desafían modelos más simples de anisotropía sísmica en la capa D′′.
- El corte en (001) se identifica como el mecanismo de deformación más probable para MgSiO(3)-ppv.
- Esta investigación proporciona una vía para mapear la deformación en el límite núcleo-manto y vincular los procesos D′′ a la dinámica del manto.
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