Relationships of the Seismicity at the Alaska Subduction Zone to Metamorphism and the Deep Fluid Regime

We examined the spatial distribution of intermediate-depth earthquakes in southern Alaska and the adjacent Aleutian Islands in relation to the deep fluid regime and volcanism. The distribution of earthquake hypocenters is studied in two variables, the depth of focus and the distance from the top of...

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Bibliographic Details
Published in:Izvestiya. Physics of the solid earth 2020-11, Vol.56 (6), p.892-899
Main Authors: Nikitina, Margarita A., Rodkin, Mikhail V., Shmakov, Ivan G.
Format: Article
Language:English
Subjects:
Dehydration
Depth of field
Distribution
Earth and Environmental Science
Earth Sciences
Earthquakes
Fronts
Geophysics/Geodesy
Isotopes
Metamorphism
Plates (tectonics)
Seismic activity
Seismicity
Spatial distribution
Subduction
Subduction (geology)
Subduction zones
Volcanic activity
Volcanism
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Summary:We examined the spatial distribution of intermediate-depth earthquakes in southern Alaska and the adjacent Aleutian Islands in relation to the deep fluid regime and volcanism. The distribution of earthquake hypocenters is studied in two variables, the depth of focus and the distance from the top of the slab. This approach shows that seismic activity is concentrated at 10–15 and 20–25 km from the top of the downgoing plate. Clusters of seismicity such as these cannot be due to slippage along the boundary between the continental block and the slab. In addition, extended structures of sharply increased seismic activity were found. Their location fits certain quasi-linear relations between pressure and temperature, and can mark metamorphic fronts in the subducted plate. Besides, the spatial earthquake distribution has a peak that appears to be related to active recent volcanism. It can be caused by active dehydration reactions in the subduction plate. These empirical findings testify in favor of the fluid-metamorphic model of earthquakes origin.
ISSN:1069-3513
1555-6506
DOI:10.1134/S1069351320060063