Fault motion in the large earthquakes of the Kurile--Kamchatka arc and of the Kurile--Hokkaido corner

Journal Article · Sat Jan 10 04:00:00 EST 1976 · J. Geophys. Res.; (United States)

DOI:https://doi.org/10.1029/JB081i002p00297· OSTI ID:7342985

Stauder, W ^[1]; Mualchin, L

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1. St. Louis Univ.

The focal mechanisms of 120 larger earthquakes (m/sub b/ greater than or equal to 5.7) of the Kurile-Kamchatka arc for the period 1962-1973 illustrate particular features of the subduction of the Pacific plate beneath this island arc system. The faulting characteristic of normal-depth earthquakes is consistent with convergence of the oceanic plate in the direction N60/sup 0/W with respect to the continental plate. Shallower foci under the trench are tensional; those seaward of the trench and related to the Hokkaido rise are compressional. Intermediate-depth foci separate into those which represent either axial compression with respect to the plate or axial tension. The occurrence of the two types in close spatial proximity may possibly correspond (cf. Veith, 1974b) to differences in the orientation of principal stresses due to volume change across the olivine-spinel phase transition boundary. In the northern Kuriles, deep-focus earthquakes are compressional with respect to the axis of the descending plate. In the vicinity of the Hokkaido corner, east-west striking normal faults and northward dipping tension axes in intermediate- and deep-focus earthquakes imply hinge faulting and contortion of the Pacific plate between the more moderately dipping Japanese segment of the plate and the steeper dipping Kurile Islands segment. Recurrent Tokachi--Oki earthquakes seaward of the Hokkaido corner indicate that the direction of convergence of the Pacific plate is unaffected by the presence of the junction of the two island arc systems.

• OSTI ID: 7342985
• Journal Information: J. Geophys. Res.; (United States), Journal Name: J. Geophys. Res.; (United States) Vol. 81:2; ISSN JGREA
• Country of Publication: United States
• Language: English

Related Subjects

58 GEOSCIENCES
580201* -- Geophysics-- Seismology & Tectonics-- (1980-1989)
EARTHQUAKES
EUROPE
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MOTION
SEISMIC EVENTS
TECTONICS
USSR