Rodgers Creek fault (Class A) No. 32
Last Review Date: 1998-09-10
Compiled in cooperation with the California Geological Survey
citation for this record: Hart, E.W., compiler, 1998, Fault number 32, Rodgers Creek fault, in Quaternary fault and fold database of the United States: U.S. Geological Survey website, https://earthquakes.usgs.gov/hazards/qfaults, accessed 05/04/2024 07:29 PM.
| Synopsis |
Holocene dextral fault. Important branch of the larger San Andreas fault system connecting, by means of right steps, the Hayward fault [55] to the south and the Maacama fault [30] to the north. Detailed geologic and geomorphic mapping by Brown (1970 #1320; 1971 #5273), Fox and others (1973 #5253), Sims and others (1973 #5263), Blake and others (1971 #4797; 1974 #5272), Huffman and Armstrong (1980 #4862), Hart (1982 #5267; 1992 #5268), Bryant (1982 #5251), and Jennings (1988 #5266) identified recently active traces of the fault. Based on surface traces, the fault was zoned under the Alquist-Priolo Earthquake Fault Zoning Act from Windsor Creek on the north almost to San Pablo Bay (California Division of Mines and Geology, 1983 #5275; 1993 #5298). Two paleoseismic investigations may have identified the last three earthquakes and determined a slip rate of 6.4–10.4 mm/yr for the south part of the fault (Schwartz and others, 1992 #5264) and several site investigations under the Alquist-Priolo Act have located or verified Holocene-active fault traces (Hart, 1982 #5267; 1992 #5268). High-precision theodolite surveys conducted since 1980 have not indicated any fault creep (Galehouse, 1995 #5500). |
| Name comments |
Wood (1916 #5929) showed a northwest-striking structure that he referred to as the "Eureka-Ukiah-San Pablo line", the southern part of which generally corresponds to the location of the Rodgers Creek fault. The Rogers Creek fault was first mapped and described by Dickerson (1922 #5271) as the northwest extension of the "Hayward Rift." Also shown on the small-scale map of Willis and Wood (1922 #5256) as an active or probable active fault extending from Santa Rosa to San Pablo Bay. Southern parts of the fault were mapped in greater detail and named the Rodgers Creek fault by Weaver (1949 #5262) based on "topographic peculiarities" along Rodgers Creek. The northern part of the fault (north of Santa Rosa) was first mapped in detail and designated the Healdsburg fault [31] by Gealey (1951 #4854), who recognized recent dextral slip near Windsor, but extended the fault as a structural feature for 17 km northwest of Healdsburg. The active part of the Healdsburg fault [31] was extended southward to Santa Rosa by Brown (1970 #1320) and Huffman and Armstrong (1980 #4862), as well as others. Recognizing the apparent continuity between the Rodgers Creek fault and the southern Healdsburg fault [31] across a 1-km-wide right step at Santa Rosa, Herd and Helley (1976 #510), Herd (1978 #5269), Hart (1982 #5267; 1992 #5268), Jennings (1994 #2878) and the Working Group on Northern California Earthquake Potential (1996 #1216) applied the name "Rodgers Creek" to both faults. The central and northern parts of the Healdsburg fault [31] do not exhibit geomorphic evidence of Holocene offset and, thus, are not considered part of the Rodgers Creek fault. Fault ID: Refers to number 149 (Rodgers Creek fault) of Jennings (1994 #2878) and number H3 (Rodgers Creek fault) of the Working Group on Northern California Earthquake Potential (1996 #1216). |
| County(s) and State(s) |
SONOMA COUNTY, CALIFORNIA |
| Physiographic province(s) |
PACIFIC BORDER |
| Reliability of location |
Good Compiled at 1:24,000 scale. Comments: Locations based on digital revisions to Jennings (1994 #2878) using original mapping by Brown (1971 #5273), Herd and others (1977 #4858), Herd (1978 #5270), and California Division of Mines and Geology (1983 #5275; 1993 #5298) at 1:24,000.
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| Geologic setting |
Dextral faulting offsets upper Cenozoic volcanic and sedimentary rock units along the southwestern flanks of Sonoma Mountains and unnamed hills to the north (Huffman and Armstrong, 1980 #4862). Dextral offset is estimated to be 28±3 km in the past 6 m.y. (Sarna-Wojcicki, 1992 #5265). The southern end of the fault connects with the Hayward fault [55] via a 6-km-wide right stepover under San Pablo Bay (Wright and Smith, 1992 #5258). The northern end apparently connects with the Maacama fault [30] via a complex right stepover of about 6 km. Historical dextral slip is indicated by first-motion studies for the 1969 Santa Rosa earthquakes (M5.6 and 5.7) by Wong and Bott (1995 #5260), who also documented a complex but continuous zone of seismicity for the northern half of the Rodgers Creek fault and its stepover to the Maacama fault.
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| Length (km) | 56 km. |
| Average strike | N34°W |
| Sense of movement |
Right lateral
Comments: Nearly pure dextral slip based on geology (Sarna-Wojcicki, 1992 #5265) and geomorphic features (Bryant, 1982 #5251; Hart, 1982 #5267; 1992 #5268). Possible down to the southwest displacement component at southern end (Wright and Smith, 1992 #5258).
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| Dip |
90°
Comments: Fault is assumed to be vertical based on geomorphic features, but locally may dip steeply to the northeast (e.g., Wright and Smith, 1992 #5258); trenches at several sites support vertical to near vertical dips.
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| Paleoseismology studies |
A small drainage channel opposite Shiloh Road (site 32-1) was noted to be sharply offset about 1 m in a right-lateral sense with about 10 m of offset in the adjacent young (undated) terrace deposit. The small (1-m) offset may represent the last rupture event in late Holocene time (E.W. Hart and F.H. Swan, 1998, unpub. field observations). Trenches at the Triangle G site (site 32-2) along Rodgers Creek exposed evidence of three events in the past 1,000 yr (Schwartz and others, 1992 #5264). Trenches at another site 0.5 km to the southeast at Beebe Ranch (site 32-3) exposed dextrally offset channels in late Holocene alluvial deposits that allowed researchers to determine a slip rate of 6.4–10.4 mm/yr in the past 775 yr (Budding and others, 1991 #5274; Schwartz and others, 1992 #5264). Surface displacement of 2 m (+0.3, -0.2 m) was measured for the most recent event at the Beebe Ranch site (32-3) (Schwartz and others, 1992 #5264).
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| Geomorphic expression |
Well-defined linear troughs and scarps, sag ponds, shutter ridges, sidehill benches, and dextrally deflected and beheaded drainages indicate a relatively high Holocene dextral slip rate (Bryant, 1982 #5251; Hart, 1982 #5267; Schwartz and others, 1992 #5264; 1992 #5268). Locally, the fault is obscured by large landslides. The southern end is concealed under late Holocene bay mud (Wagner and Bortugno, 1982 #4870) and the Santa Rosa stepover is concealed by young alluvium.
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| Age of faulted surficial deposits | Faulted alluvium and soil are exposed in trenches at several sites both north and south of Santa Rosa (unpublished consultants' reports, partly summarized by Hart, 1982 #5267; 1992 #5268). Soils and alluvium at two paleoseismic trench sites (32-2 and 32-3) have been identified as latest Holocene (Schwartz and others, 1992 #5264). |
| Historic earthquake | |
| Most recent prehistoric deformation |
latest Quaternary (<15 ka)
Comments: Historical records and charcoal radiocarbon dates from the top of the faulted section at the Shiloh Road site (32-1) place the most recent event between 1670 A.D. and about 1800 A.D. (S. Hecker, written commun., Oct. 2001).
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| Recurrence interval |
230 yr (late Holocene)
Comments: Schwartz and others (1992 #5264) determined a recurrence interval of 131–370 yr (best estimate of 230 yr) at the Beebe Ranch site (32-3). The three events recorded at the nearby Triangle G Ranch site (32-2) are consistent with this estimate. |
| Slip-rate category |
Greater than 5.0 mm/yr
Comments: 6.4–10.4 mm/yr at Beebe Ranch site (32-3) (Schwartz and others, 1992 #5264). Slip rate based on measured offset of 5.1–7.2 m of alluvium-filled channels and radiocarbon dating by Schwartz and others (1992 #5264) (specifics not given) who modified the results of Budding and others (1991 #5274) and Lienkaemper and Borchardt (1996 #5297). |
| Date and Compiler(s) |
1998
Earl W. Hart, California Geological Survey |
| References |
#5272 Blake, M.C., Bartow, J.A., Frizzell, V.A., Jr., Schlocker, J., Sorg, D., Wentworth, C.M., and Wright, R.H., 1974, Preliminary geologic map of Marin and San Francisco Counties and parts of Alameda, Contra Costa and Sonoma Counties, California, San Francisco Bay Region Environment and Resources Planning Study: U.S. Geological Survey Miscellaneous Field Studies Map MF-574 (Basic Data Contribution 64), scale 1:62,500. #4797 Blake, M.C., Jr., Smith, J.T., Wentworth, C.M., and Wright, R.H., 1971, Preliminary geologic map of western Sonoma County and northernmost Marin County, California: U.S. Geological Survey Basic Data Contribution 12, 1 pl., scale 1:62,500. #1320 Brown, R.D., Jr., 1970, Faults that are historically active or that show evidence of geologically young surface displacement, San Francisco Bay region, a progress report—Oct. 1970: U.S. Geological Survey Open-File Map (U.S. Department of the Interior and U.S. Department of Housing and Urban Development Basic Data Contribution 7), 2 sheets, scale 1:250,000. #5273 Brown, R.D., Jr., 1971, Recently active traces of the Rodgers Creek fault, Santa Rosa, Cotati, Glen Ellen, Petaluma River, and Sears Point quadrangles, California: Unpublished annotated maps of U.S. Geological Survey, scale 1:24,000. #5251 Bryant, W.A., 1982, Chianti, Healdsburg, Alexander, Maacama and related faults, Sonoma County: California Division of Mines and Geology Fault Evaluation Report 135 microfiche copy in California Division of Mines and Geology Open-File Report 90-10, 18 p., scale 1:24,000, parts of 5 quadrangles, scale 1:24,000. #5274 Budding, K.E., Schwartz, D.P., and Oppenheimer, D.H., 1991, Slip rate, earthquake recurrence, and seismogenic potential of the Rodgers Creek fault zone, northern California: Initial results: Geophysical Research Letters, v. 18, p. 447-450. #5275 California Division of Mines and Geology, 1983, Revised official maps of earthquake fault zones, Healdsburg, Mark West Springs, Santa Rosa, Cotati, Glen Ellen, Petaluma River, and Sears Point quadrangles: , scale 1:24,000. #5298 California Division of Mines and Geology, 1993, Revised official maps of earthquake fault zones, Mark West Springs quadrangle: , scale 1:24,000. #5271 Dickerson, R.E., 1922, Tertiary and Quaternary history of the Petaluma, Point Reyes and Santa Rosa quadrangles: Proceedings of the California Academy of Sciences, v. 11, no. 19, p. 529-601, pl. 17-41. #5253 Fox, K.F., Sims, J.D., Bartow, J.A., and Helley, E.J., 1973, Preliminary geologic map of eastern Sonoma County and western Napa County, California: San Francisco Bay Region Environment and Resources Planning Study: U.S. Geological Survey Miscellaneous Field Studies Map MF-483 (Basic Data Contribution 56), scale 1:62,500. #5500 Galehouse, J.S., 1999, Theodolite measurement of creep rates on San Francisco Bay region faults: U.S. Geological Survey, Summaries of National Earthquake Hazards Reduction Program, v. 40, USGS Contract 99-HQ-GR-0084 (electronic version available on line at http://erp-web.er.usgs.gov). #4854 Gealey, W.K., 1951, Geology of the Healdsburg quadrangle, California: California Department of Conservation, Division of Mines and Geology Bulletin 161, 50 p., 3 pls., scale 1:62,500. #5267 Hart, E.W., 1982, Rodgers Creek fault, Sonoma County: California Division of Mines and Geology Fault Evaluation Report 141, microfiche copy in California Department of Conservation, Division of Mines and Geology Open-File Report 90-10, 20 p., scale 1:24,000. #5268 Hart, E.W., 1992, Recently active traces of the Rodgers Creek fault, Sonoma County, California: California Department of Conservation, Division of Mines and Geology Open-File Report 92-7, 18 p., scale 1:24,000. #5269 Herd, D.G., 1978, Neotectonic framework of central coastal California and its implications to microzonation of the San Francisco Bay Region: Proceedings of the Second International Conference on Microzonation, v. 1, p. 231-240. #5270 Herd, D.G., 1978, Map of Quaternary faulting along the southern Rodgers Creek fault zone, Glen Ellen, Petaluma River, and Sears Point 7.5-minute quadrangles: California: U.S. Geological Survey Open-File report 78-306, scale 1:24,000. #510 Herd, D.G., and Helley, E.J., 1976, Faults with Quaternary displacement northwestern San Francisco Bay region, California: U.S. Geological Survey Miscellaneous Field Studies Map MF-818, 1 sheet, scale 1:125,000. #4858 Herd, D.G., Helley, E.J., and Rogers, B.W., 1977, Map of Quaternary faulting along the southern Maacama fault zone, California: U.S. Geological Survey Open-File Report 77-453, 7, scale 1:24,000. #4862 Huffman, M.E., and Armstrong, C.F., 1980, Geology for planning in Sonoma County: California Division of Mines and Geology Special Report 120, 31 p., 5 pls., scale 1:62,500. #5266 Jennings, C.W., 1988, Preliminary geologic map of the northwest quarter of the Santa Rosa quadrangle, Sonoma County, California: California Division of Mines and Geology Open-File Report 88-5, scale 1:1,000. #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. #5297 Lienkaemper, J.J., and Borchardt, G., 1996, Holocene slip rate of the Hayward fault at Union City, California: Journal of Geophysical Research, v. 101, no. B3, p. 6099-6108. #5265 Sarna-Wojcicki, A.M., 1992, Long-term displacement rates of the San Andreas fault system in northern California from the 6-Ma Roblar tuff [abs.], in Borchardt, G., and others, eds., Proceedings of the Second Conference on Earthquake Hazards in the eastern San Francisco Bay area: California Department of Conservation, Division of Mines and Geology Special Publication 113, p. 29-30. #5264 Schwartz, D.P., Pantosti, D., Hecker, S., Okumura, K., Budding, K.E., and Powers, T., 1992, Late Holocene behavior and seismogenic potential of the Rodgers Creek fault zone, Sonoma County, California, in Borchardt, G., and others, eds., Proceedings of the Second Conference on Earthquake Hazards in the eastern San Francisco Bay area: Division of Mines and Geology Special Publication 113, p. 393-398. #5263 Sims, J.D., Fox, K.F., Jr., Bartow, J.A., and Helley, E.J., 1973, Preliminary geologic map of Solano County and parts of Napa, Contra Costa, Marin, and Yolo Counties, California—San Francisco Bay Region Environment and Resources Planning Study: U.S. Geological Survey Miscellaneous Field Studies Map MF-484 (Basic Data Contribution 54), scale 1:62,500. #4870 Wagner, D.L., and Bortugno, E.J., compilers, 1982, Geologic map of the Santa Rosa quadrangle, California, California: California Division of Mines and Geology Regional Geologic Map 2A, 1 sheet of 5, scale 1:250,000. #5262 Weaver, C.E., 1949, Geology of the Coast Ranges immediately north of the San Francisco Bay region: Geological Society of America Memoir 35, 242 p., 24 pls., scale 1:62,500 (geology summarized and maps and sections reprinted in California Division of Mines Bulletin 149). #5256 Willis, B., and Wood, H.D., 1922, Fault map of the state of California: Seismological Society of America, scale 1:506,880. #5260 Wong, I.G., and Bott, J.D.J., 1995, A new look back at the 1969 Santa Rosa, California, earthquakes: Bulletin of the Seismological Society of America, v. 85, p. 334-343. #5929 Wood, H.O., 1916, California earthquakes, a synthetic study of recorded shocks: Bulletin of the Seismological Society of America, v. 6, p. 55-180. #1216 Working Group on Northern California Earthquake Potential (WGNCEP), 1996, Database of potential sources for earthquakes larger than magnitude 6 in northern California: U.S. Geological Survey Open-File Report 96-705, 40 p. #5258 Wright, T.L., and Smith, N., 1992, Right step from the Hayward fault to the Rodgers Creek fault beneath San Pablo Bay, in Borchardt, G., and others, eds., Proceedings of the Second Conference on Earthquake Hazards in the Eastern San Francisco Bay Area: California Department of Conservation, Division of Mines and Geology Special Publication 113, p. 407-417. |