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Search indexed USGS publications on groundwater, aquifers, geologic maps, mineral resources and earthquakes. Explore source records by subject and place.

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At least 937 records · Page 52Linked to original sources
USGS1981

Eastern Gulf of Alaska seismicity: Annual report to the National Oceanic and Atmospheric Administration for April 1, 1980, through March 31, 1981

The objective of this research is to collect and analyze data on earthquake activity in the northeast Gulf of Alaska (NEGOA) and adjacent onshore areas in order to develop a better regional seismotectonic model and more accurately assess the earthquake potential. This information is critical to the establishment of criteria for the safe development of oil and gas. Large (M s > 7) historical earthquakes have occurred in and around the NEGOA, and recent studies suggest that the NEGOA is a likely site for a magnitude 8 or larger earthquake to occur within the next two or three decades. A great earthquake (Ms>8) associated with low-angle oblique underthrusting of the sea floor beneath continental shelf could be accompanied by strong ground shaking throughout much of the eastern Gulf of Alaska, possibly from Cross Sound to Kayak Island (Page, 1975), and could trigger tsunamis, seiches, and submarine slumping, any of which could be hazardous to offshore and coastal structures (Meyers, 1976).

Alaska↗
USGS1983

Geochemistry and economic potential of massive sulfide deposits from the eastern Pacific Ocean

Bulk chemical analyses are performed for major and minor elements using a variety of techniques on a suite of 9 samples of sea floor massive sulfide deposits from 21?N EPR, Juan de Fuca Ridge and Galapagos Rift. Results indicate that deposits at 21?N and Juan de Fuca are very similar despite a geographic separation of 2300 km and are composed primarily of Zn, Fe, and S, with important minor concentrations of Ag, As, Cd and Ge. The Galapagos Rift massive sulfide is primarily Fe, Cu and S and with important minor contents of only Co and Mo. Au is low, ranging from below detection up to 0.17 ppm. Pt group metals are very low, and average about 0.001 ppm. Consideration of enrichment factors and relative metal abundance suggests that MORB is a sufficient source for all the metals enriched in the sea floor deposits. The economically important metals for the 21?N and Juan de Fuca deposits are primarily Zn and Ag, (97%) with potential by-products of Cu, Cd and possibly, Ge. For the Galapagos Rift, the primary value is with Cu (86%) with potential by-products of Co and Mo. The Galapagos Rift deposit is similar to, but contains about twice the Cu content, of typical ore from the Skouriotisa mine of the Troodos complex of Cyprus. The grade of the 21?N/Juan de Fuca deposits is 4 times greater than that of the Galapagos Rift and about twice that of prime deep-sea manganese nodules.

Open-File Report↗