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Imagen de reflexión sísmica de la base de una placa tectónica

T A Stern¹, S A Henrys², D Okaya³

¹Institute of Geophysics, Victoria University, Salamanca Road, Wellington 6140, New Zealand.

|February 6, 2015

Resumen

Las imágenes sísmicas de alta resolución revelan un canal de baja viscosidad en el límite litosférico-astenosférico (LAB). Este canal, que probablemente contiene fundidos o volátiles, desacopla las placas tectónicas, lo que permite la tectónica de placas.

Área de la Ciencia:

La geofísica es la geofísica.
La tectónica es la tectónica.
Sismología Sismología Sismología.

Sus antecedentes:

La tectónica de placas describe la superficie de la Tierra como placas litosféricas en movimiento.
El límite litosférico-astenosférico (LAB) en la base de estas placas sigue siendo poco conocido.
Las imágenes anteriores del LAB utilizaban ondas telesísmicas, lo que limitaba la resolución estructural.

Objetivo del estudio:

Para obtener imágenes de la base de una placa oceánica subductora con una resolución sin precedentes.
Investigar la estructura y las propiedades del límite litosférico-astenosférico (LAB).
Para proporcionar evidencia de los mecanismos que facilitan la tectónica de placas.

Principales métodos:

Utilizó ondas sísmicas generadas por la explosión con una longitud de onda de ~ 0.5 km para imágenes de alta resolución.
Analizó los reflejos de ondas P de la base de una placa oceánica que se sumerge debajo de Nueva Zelanda.
Creó una imagen sísmica de 80 km de ancho de la base de la placa de subducción.

Principales resultados:

Se identificó una abrupta transición de la velocidad de las ondas sísmicas (<1 km de espesor) a una profundidad de ~100 km, sumergiéndose a ~15°.
Se observó una disminución de 8 ± 3% en la velocidad de la onda P a través de la frontera.
Se detectó un reflejo más profundo que indica que la disminución de la velocidad se limita a un canal, interpretado como una zona rica en fundido / volátil.

Conclusiones:

Los datos de alta resolución proporcionan evidencia directa de un canal de baja viscosidad en el LAB.
Este canal desacopla la placa litosférica del flujo del manto subyacente.
La existencia de tal canal es crucial para la mecánica de la tectónica de placas.

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