T phases from 80 Alaskan earthquakes, March 28-31, 1964

1965 ◽  
Vol 55 (1) ◽  
pp. 59-63
Author(s):  
John Northrop
Keyword(s):  
Continental Shelf ◽  
Island Area ◽  
Kodiak Island ◽  
Phase Signal ◽  
T Phase

Abstract A large T-phase signal was received at Pt. Sur, California, from the Alaskan earthquake of March 28, 1964. Additional T phases were received from 90 per cent of the 80 aftershocks studied in the Kodiak Island area. The largest T phases were received from hypocenters beneath the upper portion of the continental shelf.

scholarly journals Tertiary formations in the Kodiak Island area, Alaska, and their petroleum reservoir and source-rock potential

10.14509/30 ◽  
1978 ◽  
Author(s):  
W. M. Lyle ◽  
J. A. Morehouse ◽  
I. F. Palmer ◽  
J. G. Bolm ◽  
G. W. Moore ◽  
...  
Keyword(s):  
Source Rock ◽  
Petroleum Reservoir ◽  
Island Area ◽  
Kodiak Island

Earthquake activity at the Kodiak continental shelf, Alaska, determined by land and ocean bottom seismograph networks

1982 ◽  
Vol 72 (1) ◽  
pp. 207-220
Author(s):  
Jeff Lawton ◽  
Cliff Frohlich ◽  
Hans Pulpan ◽  
Gary V. Latham
Keyword(s):  
Continental Shelf ◽  
Operation Time ◽  
Structural Heterogeneity ◽  
Network Data ◽  
Earthquake Activity ◽  
Ocean Bottom ◽  
Ocean Bottom Seismometer ◽  
Velocity Models ◽  
Kodiak Island ◽  
Shelf Region

abstract The spatial pattern of earthquakes determined by a combined land and ocean bottom seismometer (OBS) network in the Kodiak Island shelf region differs systematically from the pattern determined by a land network and from locations determined by the International Seismological Centre (ISC). As a part of a larger study of seismic risk on the continental shelf near Kodiak Island, we augmented the University of Alaska land network by deploying 11 recoverable OBS units south of Kodiak Island for 2 months in the summer of 1979. Despite a relatively short operation time and various instrument malfunctions, the combined network detected 19 locatable earthquakes in the shelf region. Because of the structural heterogeneity of this area, the earthquakes were located with a scheme which allowed different velocity models to be used for travel-time calculations of phases traveling to different stations in the network. The locations of earthquakes determined using data from both land and OBS networks were displaced about 12 km from the hypocenters of the same earthquakes determined using only land network data. For these events on the continental shelf, azimuthal control of the joint land-OBS network is excellent, and thus the joint land-OBS network locations are considerably more reliable than locations determined with the land network data alone. When the locations of the combined land-OBS network are compared to 15 yr of teleseismic locations reported by the ISC, the center of teleseismic activity appears to be about 20 to 30 km north of the center of activity determined in our study. This difference between locally determined and teleseismically determined location is similar to that observed in other studies of earthquakes and nuclear explosions in the Aleutian arc.

Possible refugia in the Alexander Archipelago of southeastern Alaska during the late Wisconsin glaciation

2007 ◽  
Vol 44 (2) ◽  
pp. 229-244 ◽  
Author(s):  
P E Carrara ◽  
T A Ager ◽  
J F Baichtal
Keyword(s):  
Continental Shelf ◽  
Western Hemisphere ◽  
Aerial Photographs ◽  
Western Coast ◽  
Stepping Stones ◽  
The West ◽  
Island Area ◽  
Area 6 ◽  
Early Humans ◽  
Alexander Archipelago

The interpretation of the extent of late Wisconsin glaciation in southeastern Alaska has varied between geologists and biologists. Maps and reports of the region prepared by geologists commonly indicated that late Wisconsin ice extended as a large uniform front west to the edge of the continental shelf. However, the distribution of plants and animals in the region has led many biologists to suggest that there may have been ice-free areas that served as refugia during the late Wisconsin. Based on analyses of aerial photographs, topographic maps, and bathymetric charts, in conjunction with a review of previous literature and reconnaissance fieldwork throughout the region, this study presents data supporting a limited ice extent in the Alexander Archipelago during the late Wisconsin and identifies possible ice-free areas that may have served as refugia. These areas include (1) the Fairweather Ground, (2) the Herbert Graves Island area, (3) the western coast of southern Baranof Island and adjacent continental shelf, (4) Coronation Island and the adjacent continental shelf, (5) the Warren Island area, (6) the continental shelf from west of Heceta Island to Forrester Island in the south, (7) parts of the west coast of southern Dall Island, and (8) lowland areas in southern Prince of Wales Island. The identification of these possible refugia has bearing on the recolonization of the Alexander Archipelago, as they could have served as centers of biotic dispersal upon regional deglaciation and as stepping stones for early humans with a maritime tradition entering the western hemisphere from Asia.

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