Characterization of the seismogenic process in the Aleutian island arc: III. Earthquakes at the western and eastern margins of the arc |
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| Authors: | L M Balakina A G Moskvina |
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| Institution: | 1.Schmidt Institute of Physics of the Earth,Russian Academy of Sciences,Moscow,Russia |
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| Abstract: | Parameters of the focal mechanisms of earthquakes, as well as their relations to the characteristics of seismicity and geological
structure are analyzed in the regions of the Komandorskie Islands in the west of the Aleutian arc, the Fox Islands, and the
Alaska Peninsula coast in the east of the arc. Different types of ruptures are revealed in the western and eastern parts of
the Aleutian arc. The leading type of ruptures at the southern slope of the Komandorskie Islands is steep reverse faults crossing
the arc at azimuths from submeridional to northeastern. A similar type of rupture occurs in abundance on the Rat Islands and
is predominant on the Near Islands. Steep strike-slips with small components of the normal or reverse fault manifest themselves
at the northern side of the block uplift of the Komandorskie Islands. Seismogenic ruptures in the region of the Komandorskie
Islands do not contradict geological data on the rupture tectonics on Medny and Bering islands. At the southern slope of the
Fox Islands, as well as in the Andreanof Islands, steep reverse faults striking longitudinally (along the arc) with the dip
toward the deep-sea trench are the predominant type of seismogenic ruptures. This type of seismogenic ruptures is the leading
type for the structures of island arcs with present-day volcanism; an example is the Kurile-Kamchatka island. Different types
of predominant seismogenic ruptures in the western and eastern parts of the Aleutian island arc probably reflect different
stages of the tectonic development of these regions of the arc. Possible positions and sizes of sources of the largest historical
earthquakes in the eastern part of the Aleutian island arc are considered |
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