Assessment of unconvential (tight) gas resources in Upper Cook Inlet Basin, South-central Alaska

Abstract Cook Inlet fore‐arc basin in south‐central Alaska is a large, deep (7.6 km) sedimentary basin with the Anchorage metropolitan region on its margins. From 2015 to 2017, a set of 28 broadband seismic stations was deployed in the region as part of the Southern Alaska Lithosphere and Mantle Observation Network (SALMON) project. The SALMON stations, which also cover the remote western portion of Cook Inlet basin and the back‐arc region, form the basis for our observational study of the seismic response of Cook Inlet basin. We quantify the influence of Cook Inlet basin on the seismic wavefield using three data sets: (1) ambient‐noise amplitudes of 18 basin stations relative to a nonbasin reference station, (2) earthquake ground‐motion metrics for 34 crustal and intraslab earthquakes, and (3) spectral ratios (SRs) between basin stations and nonbasin stations for the same earthquakes. For all analyses, we examine how quantities vary with the frequency content of the seismic signal and with the basin depth at each station. Seismic waves from earthquakes and from ambient noise are amplified within Cook Inlet basin. At low frequencies (0.1–0.5 Hz), ambient‐noise ratios and earthquake SRs are in a general agreement with power amplification of 6–14 dB, corresponding to amplitude amplification factors of 2.0–5.0. At high frequencies (0.5–4.0 Hz), the basin amplifies the earthquake wavefield by similar factors. Our results indicate stronger amplification for the deeper basin stations such as near Nikiski on the Kenai Peninsula and weaker amplification near the margins of the basin. Future work devoted to 3D wavefield simulations and treatment of source and propagation effects should improve the characterization of the frequency‐dependent response of Cook Inlet basin to recorded and scenario earthquakes in the region.

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INVESTIGATING SERPENTINIZATION WITHIN THE COOK INLET BASIN, ALASKA FROM THE INVERSION OF MAGNETIC DATA

10.1130/abs/2017am-297253 ◽

2017 ◽

Author(s):

Felix Ziwu ◽

◽

Kevin L. Mickus ◽

Diane I. Doser

Keyword(s):

Magnetic Data ◽

Cook Inlet ◽

Cook Inlet Basin

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The Hayes Tephra Deposits, and Upper Holocene Marker Horizon in South-Central Alaska

Quaternary Research ◽

10.1016/0033-5894(90)90056-q ◽

1990 ◽

Vol 33 (3) ◽

pp. 276-290 ◽

Cited By ~ 22

Author(s):

James R. Riehle ◽

Peter M. Bowers ◽

Thomas A. Ager

Keyword(s):

Cook Inlet ◽

Radiocarbon Dates ◽

Fine Grained ◽

South Central ◽

Inlet Region ◽

Tephra Deposits ◽

Phenocryst Content

AbstractThe most widespread of all Holocene tephra deposits in the Cook Inlet region of south-central Alaska is a set of deposits from Hayes volcano. Because of their unique phenocryst content—biotite in rare amounts and a high proportion of amphibole to pyroxene—the deposits are readily identifiable at all but the most distant sites where they are very fine grained. Eighteen radiocarbon dates from eight upland sites limit the age of the tephra set to between about 3500 and 3800 yr. The set originated at Hayes volcano in the Tordrillo Mountains 150 km northwest of Anchorage; seven or possibly eight closely succeeding deposits, low-silica dacite in composition, compose two main lobes that extend northeast for 400 km and south for at least 250 km from the vent. We estimate the total tephra volume to be 10 km3; multiple layers imply four to six larger and two or three smaller eruptions. The deposits are a nearly isochronous marker horizon that should be useful in future archeologic, geologic, and palynologic studies in the region.

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