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Tectónica del Holoceno tardío y paleosismicidad, zona de subducción del sur de la cascadia
Science (New York, N.Y.)
|January 10, 1992
Resumen
Los grandes terremotos de la zona de subducción, incluidos los grandes eventos que posiblemente superan la magnitud 8.4, han impactado en la región de la bahía de Humboldt, en el norte de California, en los últimos 1700 años, causando importantes desplazamientos de fallas y cambios en el nivel de la tierra.
Área de la Ciencia:
- Geología Geología Geología.
- La paleosismología es la paleosismología.
- La tectónica es la tectónica.
Sus antecedentes:
- La región de la Bahía de Humboldt es tectónicamente activa, situada cerca del límite de las placas de Gorda y Norteamérica.
- La evidencia sugiere que en el pasado grandes terremotos han ocurrido en esta región, lo que representa un riesgo sísmico significativo.
Objetivo del estudio:
- Para investigar la actividad paleosísmica del Holoceno en los sistemas de fallas de empuje en la región de la Bahía de Humboldt.
- Para determinar el momento, la magnitud y la frecuencia de los grandes terremotos pasados en el área.
Principales métodos:
- Análisis de los marcadores estratigráficos desplazados y las compensaciones de fallas en las zonas de fallas de Little Salmon y Mad River.
- La datación por radiocarbono (carbono-14) de depósitos geológicos para establecer cronologías de eventos.
- Correlación de los eventos de fallas con los indicadores regionales de hundimiento y elevación.
Principales resultados:
- Tres grandes desplazamientos (5-7 metros cada uno) en la falla de Little Salmon en los últimos 1700 años.
- Los desplazamientos son menos frecuentes y más pequeños en la zona de falla del río Mad.
- Episodios sincrónicos de hundimiento de turba de pantano, entierro de bosques fósiles y elevación de terrazas marinas, lo que indica grandes eventos sísmicos.
Conclusiones:
- Los terremotos asociados con los desplazamientos de fallas de Little Salmon fueron de al menos magnitud 7.6-7.8.
- Estos eventos probablemente representan la ruptura del límite de la placa norteamericana de Gorda, con magnitudes potenciales de 8.4 o más.
- La región de la Bahía de Humboldt ha experimentado recurrentes terremotos de gran magnitud en la zona de subducción a lo largo del Holoceno.
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