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Darrell G. Herd

Publications and source records attributed to Darrell G. Herd.

At least 19 recordsLinked to original sources
USGS1987

Subsurface stratigraphy of the eastern Hollister Valley, California

In September 1977, four cores were recovered by shallow auger drilling from Hollister Valley, California, near the Calaveras fault. The wells were drilled to search for evidence that Hollister Valley may have been occupied by a large lake during the late Pleistocene or Holocene. This small valley, near Monterey Bay, may have been dammed by a large landslide on the San Andreas fault (Jenkins, 1973; Herd and Helley, 1977). The cores sampled the first 38 m of sediment below the valley floor, but no lacustrine deposits were found at these sites; a very detailed record to Holocene alluviation in a tectonically subsiding basin.

California↗
USGS1981

The Great Tumaco, Colombia earthquake of 12 December 1979

Southwestern Colombia and northern Ecuador were shaken by a shallow-focus earthquake on 12 December 1979. The magnitude 8 shock, located near Tumaco, Colombia, was the largest in northwestern South America since 1942 and had been forecast to fill a seismic gap. Thrust faulting occurred on a 280- by 130-kilometer rectangular patch of a subduction zone that dips east beneath the Pacific coast of Colombia. A 200-kilometer stretch of the coast tectonically subsided as much as 1.6 meters; uplift occurred offshore on the continental slope. A tsunami swept inland immediately after the earthquake. Ground shaking (intensity VI to IX) caused many buildings to collapse and generated liquefaction in sand fills and in Holocene beach, lagoonal, and fluvial deposits.

Tumaco↗
USGS1979

A preliminary study of the Coyote Lake earthquake of August 6, 1979, and its major aftershocks

The August 6, 1979 earthquake (magnitude 5.7 + 0.2) was located about 1 km east of the Calaveras fault trace near Coyote Lake, at a depth of about 10 km. The spatial distribution of the aftershocks in the first 15 days and the focal mechanism of the main shock and selected aftershocks suggest that faulting took place primarily to the southeast of the main shock along a 25-km segment of the Calaveras fault zone at a depth of 4 to 12 km. The motion was right-lateral strike-slip along a nearly vertical fault plane. Discontinuous surface rupture was observed along a 14.4-km length of the recently active trace of the fault southeast of Coyote Lake, but no surface faulting was seen in the epicentral area. A maximum 5-mm fault offset was recorded near San Felipe Lake, about 16 km south of the main shock. There was no prominent foreshock activity. The cumulative number of aftershocks (N) versus magnitude (M) could be described by the equation log N= 3.33 - 0.75 M, in the magnitude range between 1 and 3.5. The number and size of aftershocks appeared to be much less than that expected for a main shock of magnitude 5.7.

California↗
USGS1979

Evidence for tectonic movement of the Las Positas Fault, Alameda County, California

On October 29, 1979, a new exposure of the Las Positas fault zone near Livermore, California, was created by excavation of a creek bank along Arroyo Seco. The face of the bank was cleaned by geologists of Lawrence Livermore Laboratory (Livermore, California) to obtain a better and more complete view of the fault. The excavation was undertaken by Lawrence Livermore Laboratory as part of a larger review of the earthquake hazards of the laboratory site. The Las Positas fault zone extends along the south side of Livermore Valley, passing just south of Lawrence Livermore Laboratory. The exposure revealed new evidence concerning not only the width of faulting in the Las Positas fault zone, but also its recency, style, and origin.

California↗
USGS1977

Map showing faults with Quaternary displacement, northeastern San Francisco Bay region, California

This map shows faults with Quaternary displacement in the northeast San Francisco Bay region of California. Faults that have been historically active or that show evidence of movement during approximately the last 2 million years (the Quaternary Period) are delineated and are classified according to the age of their last surface displacement. The map is designed to provide a synopsis of Quaternary faulting in the northeast San Francisco Bay area contributing toward an understanding of neotectonic crustal deformation in the central Coast Range of California. Future crustal movement will most likely occur along these fault breaks.

California↗
USGS1977

Preliminary report on Belair Exploratory Trench No. 10-76 near Augusta, Georgia

The Belair Exploratory Trench #10-76 was dug in October,1976, for the purpose of testing the conclusions of Prowell, O'Connor, and Rubin, 1975, and O'Connor and Prowell, 1976, concerning the time of latest movement along the Belair fault zone. The trench site is located 800 meters (2600 ft.) S27°W of the old Belair railroad station on U.S. Route 1 & 78 (see inset on Plate 1) in the southernmost clay pit of the Georgia Vitrified Brick and Clay Company. The trench was oriented almost nor-mal to the strike of the Belair fault zone (N27°E) about 100 meters (330 ft.) south of the trench exposure reported by Prowell, O'Connor, and Rubin, 1975. In this report, we are maintaining the terminology of Prowell, O'Connor, and Rubin, 1975, in defining the main fault as the fault that juxtaposes the crystalline phyllites and the Coastal Plain sediments (Plate 1 - at meter 106). Similarly, we refer to the eastside of the Belair fault zone as the upblock and the west side as the downblock.

Georgia↗