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Anomalías de velocidad sísmica anticorrelacionadas de la posperovskita en el manto más bajo
Alexander R Hutko1, Thorne Lay, Justin Revenaugh
1Earth and Planetary Sciences Department, University of California, Santa Cruz, CA 95064, USA.
Science (New York, N.Y.)
|May 24, 2008
Resumen
Las ondas sísmicas revelan cambios distintos en el manto profundo de la Tierra. Las velocidades indican una transición de fase mineral cerca del límite núcleo-manto, lo que afecta el comportamiento de las ondas sísmicas.
Área de la Ciencia:
- La geofísica es la geofísica.
- Sismología Sismología Sismología.
- Física de los minerales Física de los minerales
Sus antecedentes:
- El manto profundo de la Tierra exhibe complejas propiedades térmicas, químicas y mineralógicas.
- La caracterización sismológica precisa es crucial para comprender estas estructuras profundas de la Tierra.
- La región límite núcleo-manto es conocida por una heterogeneidad significativa.
Objetivo del estudio:
- Para caracterizar sismológicamente las estructuras en el manto más bajo de la Tierra.
- Para investigar las anomalías de la velocidad de las ondas sísmicas cerca del límite núcleo-manto.
- Comprender las implicaciones de las transiciones de fase mineral en las propiedades sísmicas.
Principales métodos:
- Análisis de más de 10.000 ondas sísmicas P y S que atraviesan el manto profundo.
- Aplicación de técnicas de apilamiento, migración y modelado.
- Resolución de las estructuras por encima del límite núcleo-manto debajo de la placa de Cocos.
Principales resultados:
- Se observó una disminución del -0,07% en la velocidad de la onda P (Vp) y un aumento del 1,5% en la velocidad de la onda S (Vs) a una profundidad de ~2570 km.
- Se detectó una disminución del -1,0% en la velocidad del sonido a granel (Vb) a la misma profundidad.
- Encontró una anticorrelación local entre las anomalías Vb y Vs, consistente con los cambios mineralógicos.
Conclusiones:
- Las anomalías sísmicas observadas se explican por la transición de la perovskita de silicato a la posperovskita.
- Esta transición aumenta significativamente el módulo de corte mientras afecta mínimamente el módulo de bulto.
- Los datos sísmicos proporcionan evidencia de la complejidad mineralógica del manto profundo y los cambios de fase.
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