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Variaciones hemisféricas en la velocidad sísmica en la parte superior del núcleo interno de la Tierra
1Department of Terrestrial Magnetism, Carnegie Institution of Washington, 5241 Broad Branch Road NW, Washington DC 20015, USA. niu@dtm.ciw.edu
Nature
|April 27, 2001
Resumen
Variaciones de la velocidad sísmica en la Tierra.
Área de la Ciencia:
- Geofísica, Sismología, Ciencias de la Tierra.
Sus antecedentes:
- Comprender la estructura de la velocidad sísmica del núcleo interno de la Tierra es crucial para elucidar los procesos de crecimiento del núcleo interno.
- Los estudios sísmicos anteriores han investigado principalmente estructuras de más de 100 km de profundidad, con datos limitados para los 100 km superiores del núcleo interno.
Objetivo del estudio:
- Para restringir las variaciones de velocidad sísmica directamente debajo del límite del núcleo interno.
- Para investigar las diferencias regionales en la velocidad sísmica dentro del núcleo interno superior.
Principales métodos:
- Análisis de las diferencias en el tiempo de viaje entre las ondas sísmicas reflejadas y transmitidas a través de la frontera del núcleo interno.
- Utilizó datos de estaciones de sismógrafos globales y redes sísmicas regionales.
- Residuos de tiempo de viaje examinados para las ondas que muestran diferentes regiones hemisféricas del núcleo interno.
Principales resultados:
- Los residuos de tiempo de viaje sistemáticos observados son aproximadamente 0,8 segundos más grandes para las ondas que muestran el "hemisferio oriental" en comparación con el "hemisferio occidental" del núcleo interno.
- No se encontró ninguna correlación entre los residuos y los ángulos de travesía de las ondas, lo que sugiere una anisotropía sísmica mínima en esta región.
- Se determinó que la velocidad sísmica isotrópica del núcleo interno oriental es aproximadamente un 0,8% más alta que la del núcleo interno occidental.
Conclusiones:
- El núcleo interno superior de la Tierra exhibe una heterogeneidad de velocidad regional significativa.
- El hemisferio oriental del núcleo interno posee una mayor velocidad sísmica isotrópica que el hemisferio occidental.
- Estos hallazgos proporcionan nuevos conocimientos sobre los procesos físicos que rigen el crecimiento y la estructura del núcleo interno.
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