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Evidencia sísmica de la sobrepresión de la corteza oceánica subducida y el sellado de fallas de megathrust
Pascal Audet1, Michael G Bostock, Nikolas I Christensen
1Department of Earth and Ocean Sciences, University of British Columbia, Vancouver, British Columbia V6T 1Z4, Canada. paudet@berkeley.edu
Nature
|January 6, 2009
Resumen
El agua en la subducción de la corteza oceánica indica un megatrust de baja permeabilidad. Los cambios en la presión del fluido impulsan la transición a una interfaz de alta permeabilidad, lo que afecta la dinámica de la zona de subducción y la sismogénesis.
Área de la Ciencia:
- La geofísica es la geofísica.
- La tectónica es la tectónica.
- Física mineral Física de los minerales
Sus antecedentes:
- El agua y los minerales hidrosos son cruciales para la geodinámica de la zona de subducción, influyendo en el debilitamiento y el deslizamiento de los límites de las placas.
- Las anomalías sísmicas revelan agua en la cuña del manto del arco anterior (serpentinización), pero su presencia en la placa subductora es menos comprendida.
Objetivo del estudio:
- Para investigar la presencia y el estado del agua dentro de la corteza oceánica subductora.
- Comprender las implicaciones de la presencia de agua para la permeabilidad de la interfaz de placas y los procesos de la zona de subducción.
Principales métodos:
- Utilizó ondas telesísmicas convertidas para analizar el comportamiento de las ondas sísmicas.
- Interpretó las anormalmente altas proporciones de Poisson dentro de la corteza oceánica subducida.
Principales resultados:
- Se observaron elevados índices de Poisson en la corteza oceánica de Cascadia subductora, lo que indica agua fluida generalizada a presiones de poro cercanas a la litostática.
- Identificó un fuerte contraste de velocidad negativa en la parte superior de la corteza oceánica, lo que sugiere una megatrust de baja permeabilidad.
- La propuesta de hidrofracturación, impulsada por la eclogitización y la serpentización, explica la transición a una interfaz de alta permeabilidad hacia abajo.
Conclusiones:
- El agua fluida omnipresente en la corteza subductora implica un sello megatrust de baja permeabilidad.
- Transiciones de permeabilidad de la interfaz de la placa debido a cambios de volumen y la hidrofracturación.
- Los hallazgos tienen implicaciones significativas para la comprensión de la sismogénesis, la estructura de la zona de subducción y los mecanismos episódicos de temblor y deslizamiento.
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