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Darrell G. Herd

Publications and source records attributed to Darrell G. Herd.

11 recordsLinked to original sources
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↗
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↗