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Un mecanismo periódico de calentamiento por cizallamiento para terremotos de profundidad intermedia en el manto
1Department of Earth and Environmental Sciences, Columbia University, Lamont Doherty Earth Observatory, Palisades, New York 10964, USA. peterk@ldeo.columbia.edu
Nature
|April 13, 2007
Resumen
Los terremotos de profundidad intermedia tienen su origen en el arrastre viscoso localizado, no solo en la deshidratación. Este nuevo modelo explica la actividad sísmica por debajo de las zonas de subducción, revelando un ciclo de inestabilidad cuasi periódico.
Área de la Ciencia:
- La geofísica es la geofísica.
- Sismología Sismología Sismología.
- La tectónica es la tectónica.
Sus antecedentes:
- Los terremotos de profundidad intermedia ocurren en zonas de subducción por debajo de la transición frágilidad-ductilidad.
- Los modelos existentes sugieren mecanismos térmicos o de deshidratación, pero estos son insuficientes para algunas ubicaciones de terremotos.
- Las altas presiones a estas profundidades hacen que la falla por fricción sea poco probable.
Objetivo del estudio:
- Proponer y modelar un mecanismo alternativo para terremotos de profundidad intermedia.
- Para explicar la actividad sísmica que se produce por debajo de la profundidad de la presencia de minerales hidratados.
Principales métodos:
- Modelado numérico de una zona de corte de grano fino dentro de un medio espacio elástico de grano grueso.
- Utilizando las leyes de flujo de olivina y simulando los efectos de calentamiento de cizallamiento.
- Incorporando las temperaturas iniciales (600-800°C) y las tasas de deformación de fondo (10−1210−15 s−1).
Principales resultados:
- El arrastre viscoso localizado se inicia rápidamente debido al calentamiento de cizallamiento, aumentando la velocidad de deformación y la temperatura.
- Las tasas de deformación superan 1 s-1 y las temperaturas alcanzan los 1.400°C, seguidas de una caída de tensión.
- El proceso da como resultado inestabilidades sísmicas cuasi periódicas bajo una deformación continua del campo lejano.
Conclusiones:
- El flujo viscoso en las zonas de corte de grano fino proporciona un mecanismo viable para los terremotos de profundidad intermedia.
- Este mecanismo explica los terremotos que ocurren a mayor profundidad de donde es posible la deshidratación.
- El modelo predice una naturaleza cíclica de estos eventos sísmicos.
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