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At least 1,441 records · Page 80Linked to original sources
USGS1975

Results of aquifer testing in the Belcourt area, Rolette County, North Dakota

The city of Belcourt, Agency headquarters for the Turtle Mountain Indian Reservation, is located in northeastern Rolette County, north-central North Dakota. At the request of the U.S. Public Health Service, the U.S. Geological Survey conducted a study in the vicinity of Belcourt to assist in location of a suitable water supply for the city.

North Dakota↗
USGS1975

Geology, physical properties, and surface effects at Discus Thrower Site, Yucca Flat, Nevada test site

Geologic studies in connection with Project Discus Thrower have furnished detailed stratigraphic and structural information about northwestern Yucca Flat. The Paleozoic rocks consist of a lower carbonate sequence, argillite of the Eleana Formation, and an upper carbonate sequence. The distribution of these rocks suggests that both top and bottom of the Eleana are structural contacts, probably thrusts or reverse faults. The overlying tuff includes several units recognized in the subsurface, such as the Fraction Tuff and tuff of Redrock Valley. Other units recognized include bedded tuff associated with the Grouse Canyon Member of Belted Range Tuff, and the Rainier Mesa and Ammonia Tanks Members of the Timber Mountain Tuff. The Timber Mountain and Grouse Canyon are extensively altered to montmorillonite (a swelling clay), possibly as a result of ponding of alkaline water. The overlying alluvium locally contains at the base a clayey, tuffaceous sandstone. Geophysical logs were used as an aid in locating geologic contacts and determining in situ physical properties. Graphic logs are presented that show the correlation of lithology and geophysical logs. Many of the rock units have characteristic log responses, but alteration within rock units affects the logs strikingly in some drill holes. The most significant surface effect of the experiment was the formation of a 4-foot fault scarp northwest of the site.

Open-File Report↗
USGS1977

Seismicity of the Pahute Mesa area, Nevada Test Site: 8 October 1975 to 30 June 1976

A total of 1,075 earthquakes occurred in the Pahute Mesa area with 2.5≤M L ≤4.9 during the period October 28, 1975, to June 28, 1976. The majority of these earthquakes are aftershocks of the nuclear events, Kasseri, Inlet, Muenster, Fontina, Cheshire, Estuary, Colby, and Pool (5.8≤M L ≤6.3). Smaller nuclear events (M L ≤5.5) on Rainier Mesa and Yucca Flat detonated in the same time period did not trigger aftershock sequences. The aftershock series were displaced laterally from ground zero and occurred deeper (at 4–6 km) than the nuclear even depth of burial (~1 km). The aftershocks appear to occur on vertical faults with approximately north-south strike.

Nevada↗