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Southern California Geology

Major Faults of Southern California
Inland Empire Region

Text from USGS Open-File Report 92-354

Right-lateral Strike-slip Fault Zones


index map of faults and basement terranes Click on this thumbnail to view an index map of faults and basement terranes in the Inland Empire region of San Bernardino and Riverside Counties. The file is a 135Kb pdf graphic that requires a portable-document file reader to examine and read. Link to Adobe Acrobat Reader to download a cost-free version of a pdf reader. Depending on your browser's setup, you may read the file now or save it to your disk.

Table of Contents for Right-Lateral Strike-Slip Faults of the Inland Empire (click on any item to jump to that section)

San Jacinto Fault Zone
San Andreas Fault Zone
San Gabriel Fault
Banning Fault

In the vicinity of the central Transverse Ranges, rocks of Peninsular Ranges type, San Gabriel Mountains type, and San Bernardino Mountains type are traversed by a series of northwest-trending strike-slip faults (fig. 1) that most workers assign to the San Andreas transform-fault system--a family of right-lateral faults that has evolved along the continental margin of western North America since middle Miocene time in response to interactions between the North American plate and various oceanic plates to the west (Atwater, 1970; Crowell, 1979; Dickinson and Snyder, 1979a,b). Youthful faults commonly viewed as modern components of the San Andreas system include the San Andreas fault proper; the San Jacinto, Whittier-Elsinore, and Newport-Inglewood faults; and various northwest-trending faults occurring in the offshore continental borderland (see Allen, 1957, p. 346; Crowell, 1975a, p. 10-11, 1981, p. 593). Older faults commonly viewed as abandoned components of the San Andreas system include the Punchbowl, San Gabriel, and Banning faults (Allen, 1957; Crowell, 1962, 1975a, 1981; Ehlig, 1976, 1981). Even older right-lateral faults that may belong to the San Andreas system include the San Juan-St. Francis and San Francisquito-Fenner-Clemens Well fault zones proposed in various forms by Smith (1977), Powell, (1981, 1986), and Joseph and others (1982b).

Right-lateral strike-slip faults in southern California are named and classified according to a hierarchical nomenclature that includes fault "strand", fault "zone", and fault "system" (Crowell, 1975a, p. 10-12): thus, the Mission Creek and Mill Creek strands (along with other fault strands) occur within the San Andreas fault zone that (along with other fault zones) occurs within the San Andreas fault system. Within this hierarchical classification, we adopt the fault nomenclature identified in Table 1 and map sheets 1 and 2.

Continue to San Jacinto Fault
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