Note: Archived report may contain descriptions that are not current.
San Jacinto fault, Coyote Creek section (Class A) No. 125d
Last Review Date: 1999-03-01
Compiled in cooperation with the California Geological Survey
citation for this record: Treiman, J.A., and Lundberg, M., compilers, 1999, Fault number 125d, San Jacinto fault, Coyote Creek section, in Quaternary fault and fold database of the United States: U.S. Geological Survey website, https://earthquakes.usgs.gov/hazards/qfaults, accessed 02/20/2019 01:49 PM.
This is the most seismically active fault in southern California, with significant earthquakes (larger than M5.5), including surface rupturing earthquakes in 1968 (M6.6 Borrego Mountain earthquake) and 1987 (M6.6 Superstition Hills and M6.2 Elmore Ranch earthquakes), and numerous smaller shocks within each of its main sections. Slip rates in the northern half of the fault system are around 12 mm/yr but are only around 4 mm/yr for faults in the southern half where strands overlap or are sub-parallel.
Sections: This fault has 7 sections. Sections taken from segments defined by Working Group on California Earthquake Probabilities (1995 #4945) and by Petersen and others (1996 #4860), and include from north to south into: San Bernardino section [125a], San Jacinto Valley section [125b], Anza section [125c], Coyote Creek section [125d], Borrego Mountain section [125e], Superstition Hills section [125f], and Superstition Mountain section [125g]. Sanders and Magistrale (1997 #6396) defined 18 segments based on inferred and observed historic ruptures and bends or steps in the continuity of the faults (these "segments" are listed under the seven sections described herein). Wesnousky (1986 #5305) divided the fault zone into nine segments, including the entire Claremont fault in the northern segment, including the Casa Loma fault with the Clark fault, and distinguishing the Hot Springs, Thomas Mountain and Buck Ridge faults as separate segments, in addition to the Coyote Creek, Borrego Mountain, Superstition Hills and Superstition Mountain sections as used by Working Group on California Earthquake Probabilities (1995 #4945).
General: San Jacinto fault named by Lawson and others (1908 #4969). Later mapping of major parts of zone by Fraser (1931 #6379), Dibblee (1954 #6376) and Sharp (1967 #6397). Major named faults within the zone include the Claremont, Casa Loma, Clark, Buck Ridge, Coyote Creek, Superstition Mountain, and Superstition Hills faults. See section discussions for more detail.
Section: Coyote Creek fault (nos. 479 & 480 of Jennings, 1994 #2878) was first mapped by R.T. Hill and named by Arnold (1918 #6373). Section herein incorporates Coyote Canyon and Coyote Ridge segments and northern 9 km of Borrego Mountain segment of Sanders and Magistrale (1997 #6396). Northern end of section is at intersection with Clark fault; southern limit of section is at northern limit of 1968 Borrego Mountain earthquake surface rupture (although aftershocks of that event extended north within this section according to Sanders (1989 #6395).
Fault ID: Refers to numbers 400 (Lytle Creek fault), 401 (San Jacinto fault), 402 (Glen Helen fault), 429 (Rialto-Colton fault), 447 (Claremont fault), 457 (Casa Loma fault), 458 (Hot Springs fault), 459 (Clark fault), 471 (Buck Ridge fault), 478 (Coyote Mountain fault), 479 & 480 (Coyote Creek fault), 504 (Superstition Hills fault), 505 (Superstition Mountain fault) and 506 (Wienert fault) of Jennings (1994 #2878); numbers 2 (Glen Helen fault), 3 (San Jacinto fault), 4 (Lytle Creek fault), 5 (Claremont fault), 6 (Casa Loma fault), 7 (Hot Springs fault), and 8 Clark fault) of Ziony and Yerkes (1985 #5931).
|County(s) and State(s)||
SAN DIEGO COUNTY, CALIFORNIA
RIVERSIDE COUNTY, CALIFORNIA
BASIN AND RANGE
|Reliability of location||
Compiled at 1:24,000 scale.
Comments: Traces based on State of California Alquist-Priolo Earthquake Fault Zone maps.
The San Jacinto fault zone is a major element of the San Andreas fault system in southern California, with historic earthquakes (if not ground rupture) associated with most of its sections. This dextral fault zone branches off from the San Andreas near Cajon pass and extends southeastward through the Peninsular Ranges for 240 km into southwestern Imperial Valley. Sharp (1967 #6397) believes that this is currently the most active strand of the San Andreas system in southern California, but is relatively young, with only about 24 km of total dextral offset. The fault zone may be divided into four principal sections: the Claremont, Clark, Coyote Creek and Superstition sections which are separated by major discontinuities (Sanders and Magistrale, 1997 #6396). The fault zone is further subdivided for seismic-hazard modeling purposes into from 5 to as many as 20 "segments" by various authors. The principal faults within the zone overlap in a right-stepping fashion, with a major overlap (50 km in length) occurring between the Clark and Coyote Creek faults.
|Length (km)||This section is 44 km of a total fault length of 244 km.|
|Average strike||(for section) versus N58°W (for whole fault)|
|Sense of movement||Right lateral|
Comments: Dip varies but is generally near vertical. Shallow to moderately northeast-dipping thrusts near the stepover to the Clark fault, and 75–81° NE. further to the south.
Coyote Creek fault marked by scarps, benches, linear and deflected drainages.
|Age of faulted surficial deposits||Pleistocene terrace deposits (Qt of Sharp, 1967 #6397).|
|Most recent prehistoric deformation||
latest Quaternary (<15 ka)
Comments: Timing of most recent paleoevent not known. Historical earthquakes include April 28, 1969, M5.8 Coyote Mountain earthquake.
175 (+158, -95) yr
Comments: Calculated recurrence by Working Group on California Earthquake Probabilities (1995 #4945); Wesnousky (1986 #5305) calculates 314 yr.
Between 1.0 and 5.0 mm/yr
Comments: 4.0±2.0 mm/yr (Working Group on California Earthquake Probabilities, 1995 #4945) extrapolated from Borrego Mountain section; Wesnousky (1986 #5305) assigned 2 mm/yr. Petersen and others (1996 #4860) assign a slip rate of 4.0 mm/yr (with minimum and maximum assigned slip rates of 2.0 mm/yr and 6.0 mm/yr, respectively) for probabilistic seismic hazard assessment for the State of California.
|Date and Compiler(s)||
Jerome A. Treiman, California Geological Survey
Matthew Lundberg, California Geological Survey
#6373 Arnold, R., 1918, Topography and fault system of the region of the San Jacinto earthquake: Bulletin of the Seismological Society of America, v. 8, p. 68-73.
#6376 Dibblee, T.W., Jr., 1954, Geology of the Imperial Valley region, California, in Jahns, R.H., ed., Geology of southern California: California Division of Mines Bulletin 170, p. 21-28.
#6379 Fraser, D.M., 1931, Geology of San Jacinto quadrangle south of San Gorgonio Pass, California—: Mining in California, California Department of Natural Resources, Division of Mines, v. 42, no. 4, p. 494-540.
#2878 Jennings, C.W., 1994, Fault activity map of California and adjacent areas, with locations of recent volcanic eruptions: California Division of Mines and Geology Geologic Data Map 6, 92 p., 2 pls., scale 1:750,000.
#4969 Lawson, A.C., chairman, 1908, The California earthquake of April 18, 1906—Report of the State Earthquake Investigation Commission: Washington, D.C., Carnegie Institution of Washington Publication 87.
#4860 Petersen, M.D., Bryant, W.A., Cramer, C.H., Cao, T., Reichle, M.S., Frankel, A.D., Lienkaemper, J.J., McCrory, P.A., and Schwartz, D.P., 1996, Probabilistic seismic hazard assessment for the State of California: California Department of Conservation, Division of Mines and Geology Open-File Report 96-08 (also U.S. Geological Open-File Report 96-706), 33 p.
#6396 Sanders, C., and Magistrale, H., 1997, Segmentation of the northern San Jacinto fault zone, southern California: Journal of Geophysical Research, v. 102, no. B12, p. 27,453-27,467.
#6395 Sanders, C.O., 1989, Fault segmentation and earthquake occurrence in the strike-slip San Jacinto fault zone, California, in Schwartz, D.P., and Sibson, R.H., eds., Proceedings of workshop XLV—Fault segmentation and controls of rupture initiation and termination: U.S. Geological Survey Open-File Report 89-315, p. 324-349.
#6397 Sharp, R.V., 1967, San Jacinto fault zone in the Peninsular Ranges of southern California: Geological Society of America Bulletin, v. 78, p. 705–730.
#5305 Wesnousky, S.G., 1986, Earthquakes, Quaternary faults, and seismic hazards in California: Journal of Geophysical Research, v. 91, no. B12, p. 12,587-12,631.
#4945 Working Group on California Earthquake Probabilities, 1995, Seismic hazards in southern California—Probable earthquakes, 1994 to 2024: Bulletin of the Seismological Society of America, v. 85, no. 2, p. 379-439.
#5931 Ziony, J.I., and Yerkes, R.F., 1985, Evaluating earthquake and surface faulting potential, in Ziony, J.I., ed., Evaluating earthquake hazards in the Los Angeles region—An earth-science perspective: U.S. Geological Survey Professional Paper 1360, p. 43–91.