Elsinore fault zone, Julian section (Class A) No. 126e
Last Review Date: 1998-12-01
citation for this record: Treiman, J.A., compiler, 1998, Fault number 126e, Elsinore fault zone, Julian section, in Quaternary fault and fold database of the United States: U.S. Geological Survey website, https://earthquakes.usgs.gov/hazards/qfaults, accessed 05/13/2024 02:06 PM.
| 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: Section is double stranded and includes Earthquake Valley fault (#482), Elsinore fault (#483) and unnamed faults (#470) of Jennings (1994 #2878). Northwestern extension of the Earthquake Valley fault is the Agua Tibia fault; northern end of section is at change in strike between Agua Tibia Mountain and Pala Mountain; southern end is at left-step at Tierra Blanca Mountain; portion of Earthquake Valley fault in San Felipe Valley was shown by Ellis and Lee (1919), called San Felipe fault by Merriam (1958 #6422) and referred to as San Felipe Valley fault by Smith (1979 #6435), probably to avoid confusion with the separately named pre-Quaternary San Felipe fault about 5 km to the east as shown by Jennings (1994 #2878);"Earthquake Valley fault" appears in Dibblee (1954 #6376) and Jahns (1954 #6417) and probably has earlier origins. 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). |
| County(s) and State(s) |
SAN DIEGO COUNTY, CALIFORNIA |
| Physiographic province(s) |
LOWER CALIFORNIAN BASIN AND RANGE PACIFIC BORDER |
| Reliability of location |
Good Compiled at 1:24,000 scale. Comments: Location of Holocene traces adapted from State of California Alquist-Priolo Earthquake Fault Zone maps (1:24,000 - Agua Caliente Springs, Earthquake Valley, Julian, Mesa Grande, Monument Peak, Ranchita and Warners Ranch quadrangles) using additional information from Magistrale and Rockwell (1996 #1230), Clark (1982 #1251), and Smith (1979 #6435).
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| 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).
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| Length (km) | This section is 79 km of a total fault length of 306 km. |
| Average strike | N56°W (for section) versus N51°W (for whole fault) |
| Sense of movement |
Right lateral, Reverse
Comments: Vaughan and Rockwell (1986 #6443) note thrust component introduced at the bend in the fault zone south of Agua Tibia Mountain and Clark (1982 #1251) discusses the evidence for vertical displacements possibly overshadowing dextral offset. Todd and Hoggatt (1979 #6440) argued for principally vertical displacements on the southern part of this section. Both extensional and compressional effects are discussed in the literature, probably related to a compressional left-step at the northern end of the section, around Agua Tibia Mountain, and, at the south end of the section, an older extensional right-step from the Earthquake Valley fault to the Coyote Mountain section [126f] (Magistrale and Rockwell, 1996 #1230).
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| Dip |
near-vertical to 45°, NE
Comments: Seismicity and outcrop pattern are suggestive of a high-angle fault (Merriam, 1958 #6422; Magistrale and Rockwell, 1990 #6421; Magistrale and Rockwell, 1996 #1230); shallower northeast dip is indicated, but not quantified at northern end, south of Agua Tibia Mountain (Vaughan and Rockwell, 1986 #6443).
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| Paleoseismology studies |
Site 126-12 at south end of Lake Henshaw: trench across low scarp exposed sediments deformed by underlying shear zone (Thorup, 1997 #6438) with evidence for at least two events.
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| Geomorphic expression |
Geomorphic expression of the fault is weaker in this double-stranded section than sections to the north or south, but includes dextrally deflected drainages, shutter ridges, hillside benches and scarps in alluvium (Magistrale and Rockwell, 1996 #1230); some stretches are largely erosional in expression (Clark, 1982 #1251); Smith (1979 #6435; 1979 #6436) observed numerous offset and beheaded drainages, benches and scarps along both the main Elsinore fault and the Earthquake Valley fault.
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| Age of faulted surficial deposits | Holocene alluvium and Quaternary alluvial deposits (Smith, 1979 #6435; Smith, 1979 #6436; Thorup and others, 1997 #6439). |
| Historic earthquake | |
| Most recent prehistoric deformation |
latest Quaternary (<15 ka)
Comments: 1.3- 2.2 ka at Lake Henshaw and 1.2?0.5 ka near Julian (Thorup, 1997 #6438).
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| Recurrence interval |
3-3.5 ka
Comments: Poorly constrained estimate from Thorup (1997 #6438) based on most recent event and previous event bracketed between 4-6.1 ka; poorly constrained interval of 340 (+290, -125) yr calculated recurrence by Working Group on California Earthquake Probabilities (1995 #4945); no recorded large earthquakes (1884 to 1999). |
| Slip-rate category |
Between 1.0 and 5.0 mm/yr
Comments: No data, but inferred here to be similar to sections to the north [126d] and south [126f]; Magistrale and Rockwell (1996 #1230) suggest slip rate is lower on individual strands due to distribution between Elsinore and Earthquake Valley faults; Earthquake Valley fault estimated to be 2?1 mm/yr by Petersen and others (1996 #4860) and 5.0 mm/yr (with minimum and maximum assigned slip rates of 3.0 mm/yr and 7.0 mm/yr, respectively) across the rest of the zone--this is probably incorporated as part of the Working Group on California Earthquake Probabilities (1995 #4945) slip rate for the Julian section. |
| 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. #1251 Clark, M.M., 1982, Map showing recently active breaks along the Elsinore and associated faults, California, between Lake Henshaw and Mexico: U.S. Geological Survey Miscellaneous Investigations I-1329, 2 sheets, scale 1:24,000. #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. #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. #6417 Jahns, R.H., 1954, Geology of the Peninsular Ranges province, southern California and Baja California, in Jahns, R.H., ed., Geology of Southern California: California Division of Mines and Geology Bulletin 170, p. 29-52. #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. #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. #6421 Magistrale, H., and Rockwell, T.K., 1990, Seismic and geomorphic evidence for two active branches of the south-central Elsinore fault zone [abs.]: Eos, Transactions of the American Geophysical Union, v. 71, no. 43, p. 1633. #6422 Merriam, R., 1958, Geology and mineral resources of Santa Ysabel quadrangle, San Diego County, California: California Division of Mines Bulletin 177, 42 p., 2 pls., scale 1:62,500. #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. #6435 Smith, D.P., 1979, Part of the Elsinore fault: California Division of Mines and Geology, Fault Evaluation Report FER-84, microfiche copy in California Division of Mines and Geology Open-File Report 90-13. #6436 Smith, D.P., 1979, Earthquake Valley and San Felipe Valley faults: California Division of Mines and Geology Fault Evaluation Report FER-89, microfiche copy in Division of Mines and Geology Open-File Report 90-13. #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. #6439 Thorup, K., Rockwell, T.K., Magistrale, H., and Vaughan, P., 1997, Paleoseismology of the central Elsinore fault in southern California—Preliminary results from three trench sites: Geological Society of America Abstracts with Programs, v. 29, no. 5, p. 69-70. #6440 Todd, V.R., and Hoggatt, W.C., 1979, Vertical tectonics in the Elsinore fault zone south of 33°7'30": Geological Society of America Abstracts with Programs, v. 11, no. 7, p. 528. #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. #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. |