Reflected and mode-converted seismic waves within the shallow Aleutian subduction zone, southern Kenai Peninsula, Alaska

Journal Article · Thu May 10 04:00:00 EDT 1990 · Journal of Geophysical Research; (United States)

DOI:https://doi.org/10.1029/JB095iB05p06883· OSTI ID:5014694

Stephens, C D; Page, R A; Lahr, J C ^[1]

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1. Geological Survey, Menlo Park, CA (United States)

Pronounced secondary phases observed in local recordings of quarry shots and earthquakes on the southern Kenai Peninsula, Alaska, are identified as reflected P and S and converted S-to-P phases originating within four depth ranges: in the upper few kilometers of the Cook Inlet Tertiary basin, at midcrustal depths within the overthrust North American plate, at about 35 km depth near the top of the Wadati-Benioff seismic zone in proximity to the inferred interplate megathrust, and at about 5-10 km below the megathrust in the subducted Pacific plate. Beneath the landward margin of the accreted Chugach terrane, the mid-upper plate (MUP) discontinuity dips as steeply as 20{degree}-30{degree} to the west-northwest over the depth range 12-18 km. At shallower depths it flattens and possibly arches with the crest at about 10 km depth. Similar midcrustal reflectors have been imaged about 125 km to the southwest and about 350 km to the northeast along the structural trend of the Chugach terrane. The extensive reflectors may have a common origin, possibly caused by the presence of underplated rocks. Relative amplitudes and polarities of the secondary phases originating at MUP depths provide few constraints on the nature of the discontinuity. It appears that the MUP discontinuity is seismically inactive and does not represent a brittle-ductile transition zone within the upper plate. The two converted S-to-P phases generated near the top of the subducted plate could indicate a low-velocity zone associated with subducted oceanic crust.

• OSTI ID: 5014694
• Journal Information: Journal of Geophysical Research; (United States), Journal Name: Journal of Geophysical Research; (United States) Vol. 95:B5; ISSN 0148-0227; ISSN JGREA
• Country of Publication: United States
• Language: English

Related Subjects

58 GEOSCIENCES
580000* -- Geosciences
ALASKA
ALEUTIAN ISLANDS
BENIOFF ZONE
BRITTLE-DUCTILE TRANSITIONS
CHEMICAL EXPLOSIONS
CONTINENTAL CRUST
DATA ANALYSIS
DEPTH
DEVELOPED COUNTRIES
DIMENSIONS
EARTH CRUST
EARTHQUAKES
EXPLOSIONS
FEDERAL REGION X
GEOLOGIC STRUCTURES
ISLANDS
NORTH AMERICA
OCEANIC CRUST
OPTICAL PROPERTIES
PHYSICAL PROPERTIES
PLATE TECTONICS
REFLECTIVITY
SEISMIC EVENTS
SEISMIC P WAVES
SEISMIC S WAVES
SEISMIC WAVES
SUBDUCTION ZONES
SURFACE PROPERTIES
TECTONICS
USA