Geology Reports⌕ Search

Geology topics

Philip W. Harsh

Publications and source records attributed to Philip W. Harsh.

6 recordsLinked to original sources
USGS1981

Preliminary map showing recently active breaks along the Maacama Fault zone between Hopland and Laytonville, Mendocino County, California

The southernmost 15 km of this map is a product of a study that began in 1975 as part of a study of recency of faulting in coastal California (Ziony and others, 1974; Buchanan-Banks and others, 1978; Pampeyan , 1979). In February 1975, after being shown evidence of recent faulting in the vicinity of Ukiah by E. C. Winterhalder, Principal Engineering Geologist for Harding - Lawson Associates, Pampeyan extended the study area northward to the vicinity of Willits . After the Willits earthquake of November 22, 1977 (Simon and others, 1978; Warren and others, 1979), field investigations in the epicentral area revealed a series of distressed pavements, curbs, and sidewalks all showing right-lateral offset (Harsh and others, 1978; 1981). These features traverse the city of Willits and define a line coincident with a photolineament extending southeastward from Willits. Subsequently, additional sites of distressed pavements discovered both east and north of Ukiah alone; other lineaments of the photogeologic study verified the existence of tectonic creep in the Maacama fault zone.

California↗
USGS1981

7.3 quake in Algeria reviewed.

A team from the U.S. Geological Survey studies the surface effects of the Oct. 1980 10 shock, whose epicenter was west of Algiers, near the African Plate boundary. -Authors

Geotimes↗
USGS1979

Earthquake recurrence on the Calaveras fault east of San Jose, California

Occurrence of small (3 ⩽ M L < 4) earthquakes on two 10-km segments of the Calaveras fault between Calaveras and Anderson reservoirs follows a simple linear pattern of elastic strain accumulation and release. The centers of these independent patches of earthquake activity are 20 km apart. Each region is characterized by a constant rate of seismic slip as computed from earthquake magnitudes, and is assumed to be an isolated locked patch on a creeping fault surface. By calculating seismic slip rates and the amount of seismic slip since the time of the last significant ( M ⩾ 3) earthquake, it is possible to estimate the most likely date of the next ( M ⩾- 3) event on each patch. The larger the last significant event, the longer the time until the next one. The recurrence time also appears to be increased according to the moment of smaller (2 < M L < 3) events in the interim. The anticipated times of future larger events on each patch, on the basis of preliminary location data through May 1977 and estimates of interim activity, are tabulated below with standard errors. The occurrence time for the southern zone is based on eight recurrent events since 1969, the northern zone on only three. The 95% confidence limits can be estimated as twice the standard error of the projected least-squares line. Events of M ⩾ 3 should not occur in the specified zones at times outside these limits. The central region between the two zones was the locus of two events ( M = 3.6, 3.3) on July 3, 1977. These events occurred prior to a window based on the three point, post-1969 slip-time line for the central region.

California↗