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E. E. Brabb

Publications and source records attributed to E. E. Brabb.

87 records · Page 5Linked to original sources
USGS1971

The earthquake sequence near Danville, California, 1970

Several thousand small earthquakes, with magnitudes ranging up to 4, occurred near Danville, California, during May, June, and July 1970. Seven temporary seismographs were installed near the epicentral region to augment an existing telemetered network within 1 day after the first felt earthquake. The dense concentration of 10 seismographs within 12 km of the seismic activity and the existence of a reversed seismic-refraction profile through the region permitted a very detailed study of this earthquake sequence. Over 400 events with magnitude greater than 0.5 were located with an average accuracy of ±1 km. The main earthquake region was approximately spherical: 1 km in radius, 6 km deep, and centered about 5 km southeast of Danville, 40 km east of San Francisco. Fault-plane solutions indicate that faulting associated with the earthquakes was of the right-lateral strike-slip type, with a strike of N 35°W.

California↗
USGS1971

Geologic map of Late Cenozoic deposits, Santa Clara County, California

This map is the first of several in the San Francisco Bay region showing the distribution and differentiation of the late Cenozoic alluvial, estuarine, and volcanic deposits. The sedimentary deposits of gravel, sand, silt, and clay were separated into geologic map units on the basis of their post-depositional soil development, texture, and geomorphology. Some of the geologic units are associated with different landforms having recognizable topographic expression such as alluvial fans, natural stream terraces, levees, and interfluvial basins. The relative ages of these unites were established on the basis of intensity of soil profile development, stratigraphic position, and geomorphic expression. The older deposits exhibit strongly developed soil profiles with strong horizon differentiation whereas younger deposits display minimal soil profile development, consisting primarily of organic matter accumulations near the land surface. Geomorphic expression and degree of erosion and dissection were additional criteria used to aid in the age determinations. For example, younger deposits form well-defined morphologic features such as levees, terraces, and broad, undissected alluvial fans along the margin of the bay basin and are related to present drainage patterns. The oldest deposits shown on this map (QTs) are structurally deformed by folding and faulting and therefore exhibit no original depositional geomorphic features. These deposits are not related to present drainage patterns but suggest earlier patterns much different from those existing today.

California↗
USGS1968

Geologic interpretation of reconnaissance aeromagnetic survey of northeastern Alaska

Aeromagnetic surveys of Naval Petroleum Reserve No. 4 (Woolson and others, 1962) and of a 900-square-mile area near Fairbands (Andreasen and others, 1964) are the only published aeromagnetic reports on northeastern Alaska. Several total intensity aeromagnetic profiles, primarily over the Yukon Flats in the central part of the area shown on figure 1, were obtained by the U.S. Geological Survey in 1954 and 1958 and were released for public inspection in 1960 (Andreasen, 1960a, 1960b). Most of these profiles were flown north and south at a barometric elevation of about 2,500 feet; some were flown north and south at 4,000 to 8,000 feet. All of these north-trending profiles are incorporated in this report. Six northwest-trending profiles parallel to the Yukon River between long. 147° W and 144° W. are not included.

Alaska↗