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Elsinore fault zone, Temecula section (Class A) No. 126d

Last Review Date: 1998-12-01

citation for this record: Treiman, J.A., compiler, 1998, Fault number 126d, Elsinore fault zone, Temecula section, in Quaternary fault and fold database of the United States: U.S. Geological Survey website, https://earthquakes.usgs.gov/hazards/qfaults, accessed 01/23/2019 05:48 AM.

Synopsis General: A major dextral strike-slip fault zone that is part of the San Andreas fault system. Research studies have been done to assess faulting on most of the sections, and have documented Holocene activity for the length of the fault zone with a slip rate around 4–5 mm/yr. Multiple events have only been dated on the Whittier fault and Glen Ivy North fault strand, so interaction between faults and adjacent sections is not well-known. Multiple strands within several sections mean that the studies are not always fully representative of the whole section. Numerous consulting reports (not summarized herein) that have addressed location and recency of faulting are on file with the State of California, California Geological Survey, as part of the records of their Alquist-Priolo Earthquake Fault Zoning Program.

Sections: This fault has 7 sections. Sections are selected following the segmentation from Working Group on California Earthquake Probabilities (1995 #4945) from north to south: Whittier section [126a], Chino section [126b], Glen Ivy section [126c], Temecula section [126d], Julian section [126e], Coyote Mountain section [126f], with addition of Laguna Salada section [126g] as used by Petersen and others (1996 #4860) and Chino fault (paired with the Whittier fault by Rockwell and others, 1992 #6431).Anderson and others (1989 #6372) also identified same segments, with addition of Chupamiertos and Sierra Mayor segments in Baja California (not included in this summary); Wesnousky (1986 #5305) defined four segments, combining the Whittier, Chino and Glen Ivy into his segment A, Temecula into segment B, Julian into segment C, and the Coyote Mountain and Laguna Salada sections into segment D.
Name comments General:

Section: Includes Wildomar fault (#460), Willard fault (#467) and Wolf Valley fault (#469) of Jennings (1994 #2878) and Murrieta Creek fault of (and named by) Bergmann and Rockwell (1989 #6404). Wildomar and Willard first used by Engel (1933 #6409; 1959 #6410). Wolf Valley fault was named by Kennedy (1977 #6419). Northern end of Temecula section is comprised of the Willard and Wildomar faults along south side of Lake Elsinore. Southern end of section is where the fault zone changes strike along the southern side of Agua Tibia Mountain, northeast of Pala Mountain.

Fault ID: Refers to numbers 431 (Chino fault), 444 (Whittier fault), 446 (Fresno, Tin Mine and Main Street faults), 460 (Wildomar fault), 461 (Glen Ivy North fault), 462 (Glen Ivy South fault), 467 (Willard fault), 469 (Wolf Valley fault), 470 (unnamed faults flanking Agua Tibia Mountain), 482 (Earthquake Valley), 483 & 496 (Elsinore fault), and 511 (Laguna Salada fault) of Jennings (1994 #2878); and numbers 10 (Chino fault), 12 (Whittier fault), 13 (Main Street fault), 14 (Fresno-Eagle fault), 15 (Tin Mine fault), 16 (Glen Ivy North fault), 17 (Glen Ivy South fault), 18 (Wildomar fault), 19 (Willard fault), 20 (Wolf Valley fault) of Ziony and Yerkes (1985 #5931).
Physiographic province(s) PACIFIC BORDER
Reliability of location Good
Compiled at 1:24,000 scale.

Comments: Location of fault traces modified from Kennedy (1977 #6419), Weber (1977 #6448) and Alquist-Priolo Earthquake Fault Zone maps by California Division of Mines and Geology (1:24,000 - Elsinore, Murrieta, Pala, Pechanga, Temecula and Wildomar quadrangles).

Geologic setting The Elsinore fault zone is a major dextral shear system, parallel to the southern San Andreas fault [1], that accommodates about 5 mm/yr of the Pacific-North American Plate boundary slip. The northern elements of the fault zone, the Chino and Whittier faults, bound the Puente Hills, an uplifted block of Tertiary sediments. The Glen Ivy section forms the northeast boundary of the Santa Ana Mountains, and, together with the Temecula section, forms the Elsinore trough. To the southeast the fault zone (Temecula, Julian, and Coyote Mountain sections) cuts diagonally across various Peninsular Range batholithic and pre-batholithic metamorphic terrain until it reaches the southwestern margin of the Salton Trough as the Laguna Salada fault. Total strike-slip is reported to be as much as 40 km but is more likely only 10–15 km, and total vertical separation is about 200 m (Hull and Nicholson, 1992 #6416).

Length (km) This section is 62 km of a total fault length of 306 km.
Average strike N48°W (for section) versus N51°W (for whole fault)
Sense of movement Right lateral

Comments: Greater than 10:1 horizontal to vertical slip (Hull and Nicholson, 1992 #6416; Bergmann and Rockwell, 1993 #6406). Focal mechanisms indicate dextral reverse motion in the Willard fault, in contrast to surface (trench) observations of normal component (Hull and Nicholson, 1992 #6416). Normal component of slip reported on Wildomar; reverse component on Willard, and principally normal on Murrieta Creek.

Dip Direction SW; NE

Comments: Surface dips from mapping by Kennedy (1977 #6419); near-vertical to steep NE dip is indicated by seismicity to about 13 km depth (Hull and Nicholson, 1992 #6416; Magistrale and Rockwell, 1996 #1230).

Paleoseismology studies Site 126-2, south of Lake Elsinore: a single trench exposed one of two inferred strands of the Wildomar fault. Sedimentary sections across fault do not match, and faulting extends to about 1 m from the surface. Observed deformation is interpreted to have resulted from two, and possibly three, earthquakes (Lamar and Swanson, 1981 #6420).

Site 126-5, Agua Tibia Mountain: trenching at two sites with 14C age control provided data on earthquake history (Vaughan and Rockwell, 1986 #6443; Thorup, 1997 #6438; Vaughan and others, 1999 #6446).

Site 126-6, Murrieta Creek: trench studies provided data on sense of movement, slip rate and recurrence on this secondary fault within the Elsinore fault zone (Bergmann and Rockwell, 1989 #6404).

Site 126-9, Murrieta: trench study exposed offset stream channels, providing slip rate (Rockwell, written communication, 1998).

Site 126-11, Temecula: trench study exposed offset channel, providing data on slip rate (Bergmann and Rockwell, 1993 #6406; Rockwell, written communication, 1998).

Geomorphic expression Fault zone forms southwestern boundary of Elsinore trough at nothern end; horst, scarps, sag ponds (Wildomar); linear mountain front, faceted spurs, low scarps in alluvium (Willard); offset streams, beheaded drainages, shutter ridges, graben observed at Agua Tibia Mountain.

Age of faulted surficial deposits Holocene alluvium and fan deposits; late Pleistocene Pauba Formation (Wildomar, Murrieta Creek and Wolf Valley faults); late Pleistocene Pauba Formation (Willard fault) (Kennedy, 1977 #6419).
Historic earthquake
Most recent prehistoric deformation latest Quaternary (<15 ka)

Comments: Vaughan and others (1999 #6446)(1999) estimate last event at southern end of section between 1655 and 1810 A.D.; latest event at northern part of fault section post-dates clayey horizon with 14C dates obtained from humic acids (4,330±400 yr BP) and carbon residue (4,120±260 yr BP) (Lamar and Swanson, 1981 #6420).

Recurrence interval 450–750 yr

Comments: Vaughan and Rockwell (1986 #6443) and Vaughan and others(1996 #6444) estimate 1500 year maximum average recurrence; the elapse time since the most recent event is more than 180 yr. Based on Vaughan and others (1999 #6446) a poorly constrained recurrence interval of 240 (+260, -111) yr is indicated. Working Group on California Earthquake Probabilities (1995 #4945)calculate a recurrence interval of 250–600 yr.
Slip-rate category Between 1.0 and 5.0 mm/yr

Comments: 4.2 mm/yr (+0.5/-.09) for Wildomar fault (Bergmann and Rockwell, 1993 #6406; Bergmann and others, 1993 #6407) is a partial rate; Vaughan and Rockwell (1986 #6443) give a maximum range of 1.5–7 mm/yr and a best estimate of 5 mm/yr at the southern end of this section, at Agua Tibia Mountain; Murrieta Creek fault has about 1.25 mm/yr dip-slip rate (Bergmann and Rockwell, 1989 #6404). Slip rate assigned to this part of the fault by Petersen and others (1996 #4860) for probabilistic seismic hazard assessment for the State of California was 5.0 mm/yr (with minimum and maximum assigned slip rates of 3.0 mm/yr and 7.0 mm/yr, respectively.
Date and Compiler(s) 1998
Jerome A. Treiman, California Geological Survey
References #6372 Anderson, J.G., Rockwell, T.K., and Agnew, D.C., 1989, Past and possible future earthquakes of significance to the San Diego region: Earthquake Spectra, v. 5, no. 2, p. 299-333.

#6406 Bergmann, M., and Rockwell, T.K., 1993, Preliminary assessment of the late Holocene slip rate for the Wildomar fault in Murrieta, California: Association of Engineering Geologists, 36th Annual Meeting, El Agua y La Tierra, Program and Abstracts, p. 43.

#6404 Bergmann, M.C., and Rockwell, T.K., 1989, The Murrieta Creek fault, a new branch of the Elsinore fault, Rancho California area, Riverside County, California: Geological Society of America Abstracts with Programs, v. 21, no. 5, p. 57.

#6407 Bergmann, M., Rockwell, T.K., Miles, D.K., Hirabayashi, C.K., Hushebeck, M.A., Haraden, C.C., Thomas, A., and Patterson, A., 1993, Preliminary assessment of the late Holocene slip rate for the Wildomar fault, Murrieta, California: Technical report to U.S. Geological Survey, Reston, Virginia, under Contract 14-08001-G2062, 12 p.

#6409 Engel, R., 1933, Geology of the Santa Ana Mountains and the Elsinore trough: Pasadena, California Institute of Technology, Ph.D. dissertation.

#6410 Engel, R., 1959, Geology of the Lake Elsinore quadrangle: California Division of Mines and Geology Bulletin 146, 154 p., 7 pls., scale 1:62,500.

#6416 Hull, A.G., and Nicholson, C., 1992, Seismotectonics of the northern Elsinore fault zone, southern California: Bulletin of the Seismological Society of America, v. 82, p. 800-818.

#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.

#6419 Kennedy, M.P., 1977, Recency and character of faulting along the Elsinore fault zone in southern Riverside County: California Division of Mines and Geology Special Report 131, 12 p.

#6420 Lamar, D.L., and Swanson, S.C., 1981, Study of seismic activity by selective trenching along the Elsinore fault zone, southern California: Technical report to U.S. Geological Survey, Final Technical Report 81-4 (see also U.S. Geological Survey Open-File Report 81-882), Reston, Virginia, December 1981, 50 p.

#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.

#1230 Magistrale, H., and Rockwell, T., 1996, The central and southern Elsinore fault zone, southern California: Bulletin of the Seismological Society of America, v. 86, p. 1793-1803.

#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.

#6431 Rockwell, T.K., Gath, E.M., and Gonzalez, T., 1992, Sense and rate of slip on the Whittier fault zone, eastern Los Angeles basin, California [abs.]: Association of Engineering Geologists, 35th Annual meeting, Proceedings, p. 679.

#6438 Thorup, K.M., 1997, Paleoseismology of the central Elsinore fault in southern California—Results from three trench sites: San Diego, California, San Diego State University, unpublished M.S. thesis, 94 p.

#6443 Vaughan, P., and Rockwell, T., 1986, Alluvial stratigraphy and neotectonics of the Elsinore fault zone at Agua Tibia Mountain, southern California, in Ehlig, P.L., ed., Neotectonics and faulting in southern California: Geological Society of America, 82nd Annual Meeting, Cordilleran Section, Guidebook and Volume, p. 177–191.

#6444 Vaughan, P.R., Thorup, K., and Rockwell, T.K., 1996, Paleoseismology of the central Elsinore fault near Agua Tibia Mountain, southern California, based on trenching: Geological Society of America Abstracts with Programs, v. 28, no. 5, p. 120.

#6446 Vaughan, P.R., Thorup, K., and Rockwell, T.K., 1999, Paleoseismology of the Elsinore fault at Agua Tibia Mountain, southern California: Bulletin of the Seismological Society of America, v. 89, p. 1447-1457.

#6448 Weber, F.H., Jr., 1977, Seismic hazards related to geologic factors, Elsinore and Chino fault zones, northwestern Riverside County, California: California Division of Mines and Geology Open-File Report OFR 77-4 LA, 94 p., 4 pls., scale 1:24,000 and 1:48,000.

#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.