This page describes the Cascadia subduction zone and how paleoarthquake data can help us understand earthquake and tsunami processes.
I discuss more about the geologic studies of Cascadia subduction zone seismicity on this report page, considering the 315th anniversary of the last earthquake (1700 A.D.).
The Cascadia subduction zone is an approximately 1,200-kilometer convergent plate boundary that extends from northern California to Vancouver Island, Canada (Figure 1). The Juan de Fuca and Gorda plates are subducting eastwardly below the North American plate. Seismicity, crustal deformation, and geodesy provide evidence that the Cascadia subduction zone is locked and is capable of producing a great (magnitude greater than or equal to 8.5) earthquake (Heaton and Kanamori, 1984; McPherson, 1989; Clarke and Carver, 1992; Hyndman and Wang, 1995; Flück and others, 1997).(Figure 1) 
Globally, great earthquakes along subduction zones have caused damaging ground shaking, ground rupture by upper-plate crustal faults, liquefaction, turbidites, uplifted marine terraces, and tsunamis (Plafker, 1972; Adams, 1990; Clarke and Carver, 1992; Merritts, 1989; Clague and Bobrowsky, 1994; Satake and others, 1996). Based on buried soil stratigraphy correlated with radiocarbon age data using tree ring wiggle matching and with the inference of a single orphan tsunami in Japan being caused by a single great earthquake, the entire length of the Cascadia subduction zone from Canada to California ruptured in January, 1700 A.D. (Satake and others, 1996; Jacoby and others, 1997; Yamaguchi and others, 1997).
There has been no historic Cascadia subduction zone earthquake along its entire length, but paleoseismic evidence indicates multiple earthquake cycles have occurred along the Cascadia margin over the last 8,000 years (Atwater, 1987; Hemphill-Haley, 1995; Garrison-Laney, 1998; Abramson, 1998; Kelsey and others, 2002; Witter and others, 2003; Figure 1). Evidence for Cascadia subduction zone earthquakes also has been found in Humboldt Bay Holocene stratigraphy in the form of buried soils (Carver and Burke, 1988; Vick, 1988; Clarke and Carver, 1992; Manhart, 1992; Li, 1992; Valentine, 1992; Carver and others, 1998; Leroy, 1999; Witter and others, 2002).
Quaternary deformation around Humboldt Bay has been dominated by contractile deformation due to Gorda – North America plate convergence and from northward Mendocino triple junction migration transpression (Ogle, 1953; McPherson, 1989; Carver and others, 1992b; Smith and others, 1993, and Burger and others, 2002; Williams, 2003). The deformation front of the Cascadia subduction zone lies approximately 75 kilometers offshore of Humboldt Bay (Clarke and Carver, 1992). East of the offshore deformation front is an 85- to 100-kilometer wide fold-and-thrust belt in the accretionary prism, which comes onshore in the Humboldt Bay region (Carver and Burke 1988; Clarke and Carver, 1992; inset Figure 1). Splays of the onshore fold and thrust belt include the Little Salmon fault and the Mad River fault zones (Fig 2). Transpression from Mendocino triple junction migration extends northward to at least the Table Bluff anticline (Burger and others, 2002).
Evidence for Holocene onshore tectonic activity includes (1) earthquakes on upper-plate faults of the Little Salmon fault in Salmon Creek valley and the Mad River fault zone in McKinleyville and Blue Lake (Carver and Burke, 1988), (2) sudden uplift of sections of the coast at Clam Beach (Figure 2) and Cape Mendocino (Figure 1; Clarke and Carver, 1992; Merritts, 1989, Stein and others, 1993, Carver and McCalpin, 1996), and (3) sudden subsidence along margins of Humboldt Bay and Eel River valley (Vick, 1988; Clarke and Carver, 1992; Li, 1992; Manhart, 1992; Valentine, 1992).
Here are some posters that i have presented:
2012
GEOPRISMS Cascadia Workshop southern CSZ miss-match between modern and paleogeodesy. (14MB pdf)
2011
GEOPRISMS Alaska Workshop southern CSZ miss-match between modern and paleogeodesy. (11MB pdf)
AGU fall meeting southern CSZ miss-match between modern and paleogeodesy. (23MB pdf)
Humboldt’s Ready Emergency Preparedness Fair southern CSZ Relative Sea Level. (5MB pdf)
Humboldt’s Ready Emergency Preparedness Fair Earthquake and Tsunami Hazards northern California. (4MB pdf)
2010
SSA annual meeting southern CSZ miss-match between modern and paleogeodesy. (16MB pdf)
AGU fall meeting southern CSZ miss-match between modern and paleogeodesy. (50MB pdf)
Humboldt Bay Symposium southern CSZ Relative Sea Level. (62MB pdf)
2009
SSA annual meeting southern CSZ miss-match between terrestrial and submarine paleorecord. (16MB pdf)
2005
Humboldt Bay Symposium Paleotsunami and Paleoseismic Investigation, Little Salmon fault. (5MB pdf)
2001
SSA Meeting Paleotsunami and Paleoseismic Investigation, Little Salmon fault; Panel 1. (12MB pdf)
SSA Meeting Paleotsunami and Paleoseismic Investigation, Little Salmon fault; Panel 2. (29MB pdf)
SSA Meeting Paleotsunami and Paleoseismic Investigation, Little Salmon fault; Panel 3. (22MB pdf)
SSA Meeting Paleotsunami and Paleoseismic Investigation, Little Salmon fault; Panel 4. (8MB pdf)
Here are some powerpoints that i have presented:
2012
College of the Redwoods public talk on Earthquake and Tsunami Hazards of the Mendocino Coast. (102MB pdf) Videos for this talk:
Video of tsunami generation. (3MB mpg)
Video of submarine landslide generation due to earthquakes. (0.8MB mpg)
Animation of tsunamigenesis. (8MB mpg)
Animation of tsunami modeling from Haida Gwaii tsunami. (8MB wmv)
CBC coring video off Sumatra. (8MB wmv)
2011
Humboldt Bay Initiative public talk on earthquake related deformation as it relates to local sea level. (17MB pdf)
2010
Oregon State University geosciences dept. brownbag, the discordance between terrestrial and submarine records of paleoearthquakes in northern California. (29MB pdf)
2005
Humboldt State University public lecture on earthquake hazards in northern California (follow up to the Sumatra-Andaman Earthquake and Tsunami. (20MB pdf)
2004
Humboldt State University Master’s thesis defense. (44MB pdf)
REFERENCES
Abramson, H., 1998. Evidence for Tsunamis and Earthquakes During the Last 3500 Years from Lagoon Creek, a Coastal Freshwater Marsh, Northern California: M. S. thesis, Arcata, California, Humboldt State University, 76 p.
Adams, J., 1990, Paleoseismicity of the Cascadia Subduction Zone: Evidence from Turbidites off the Oregon-Washington Margin, Tectonics, vol. 9: 569-583.
Atwater, B. F., 1987. Evidence for Great Holocene Earthquakes Along the Outer Coast of Washington State, Science, vol. 236: 942-944.
Atwater, B. F., 1997. Coastal Evidence For Great Earthquakes In Western Washington, United States Geological Survey Professional Paper 1560. United States Government Printing Office, Washington, 90 p.
Atwater, B. F., Nelson, A. R., Clague, J. L., Carver, G. A., Yamaguchi, D. K., Bobrowsky, P. T., Bourgeois, J., Darienzo, M. E., Grant, W. C., Hemphill-Haley, E., Kelsey, H. M., Jacoby, G, Nishenko, S., Palmer, S., Peterson, C. D., and Reinhart, M-A., 1995, Summary of Coastal Geologic Evidence for Past Great Earthquakes at the Cascadia Subduction Zone, Earthquake Spectra, vol. 11: 1-18.
Atwater, B., and Hemphill-Haley, E., 1997. Recurrence Intervals for Great Earthquakes of the Past 3,500 Years at Northeastern Willapa Bay, Washington, States Geological Survey Professional Paper 1576. United States Government Printing Office, Washington, 108 p.
Atwater, B. F., Yamaguchi, D. K., Bondevik, S., Barnhart, W. A., Amidon, L. J., Benson, B. E., Skjerdal, G., Shulene, J. A., and Nanayama, F., 2001, Rapid resetting of an estuarine recorder of the 1964 Alaska earthquake, Geological Society of America Bulletin, vol. 113: 1193-1204.
Bronk Ramsey C., 1995, Radiocarbon Calibration and Analysis of Stratigraphy: The OxCal Program, Radiocarbon, vol. 37: 425-430.
Bronk Ramsey C., 2001, Development of the Radiocarbon Program OxCal, Radiocarbon, vol. 43: 355-363.
Burger R. L., Fulthorpe, C. S., Austin Jr., J. A., and Gulick, S. P. S., 2002, Lower Pleistocene to present structural deformation and sequence stratigraphy of the northern continental shelf, offshore Eel River Basin, northern California, Marine Geology, vol. 185: 249-281.
Carver, G.A., 1992, Late Cenozoic Tectonics of Coastal Northern California, in Field Guide to the Late Cenozoic Subduction Tectonics and Sedimentation of Northern Coastal California, American Association of Petroleum Geologists, Pacific Section, Bakersfield, CA, GB-71 (199205), Accession No. 1996030791, 74 p.
Carver, G.A ., Burke, R. M., 1988, Final Report Trenching Investigations of Northwestern California Faults Humboldt Bay Region, United States Geological Survey Grant 14-08-0001-G1082, 53 p.
Carver, G. A., Burke, R. M., 1992, Late Cenozoic Deformation on the Cascadia Subduction Zone in the Region of the Mendocino Triple Junction, in Carver, G. A., Burke. R. M. [eds.] Friends of the Pleistocene Field Guidebook, Humboldt State University, Department of Geology, Arcata, CA, 265 p.
Carver, G. A., and McCalpin, J. P., 1996. Paleoseisomology of Compressional Tectonic Environments, in McCalpin, J. P. [ed.] Paleoseisomology, Academic Press, San Diego, CA: 183-270.
Carver, G.A., Abramson, H.A., Garrison-Laney, C.E., and Leroy, T., 1998, Paleotsunami evidence of subduction earthquakes for northern California: Final Report for Pacific Gas and Electric Co., 164 p., plus appendices.
Clague, J. J., Bobrowsky, P. T., 1994, Tsunami deposits beneath tidal marshes on Vancouver Island, British Columbia, in Geological Society of America Bulletin, vol. 106: 1293-1303.
Clague, J. J., Bobrowsky, P. T., Hutchinson, I., 2000. A review of geological records of large tsunamis at Vancouver Island, British Columbia, and implications for hazard, Quaternary Science Reviews, vol. 19: 849-863.
Clarke, S. H., and Carver, G. C., 1992. Late Holocene Tectonics and Paleoseismicity, Southern Cascadia Subduction Zone, Science, vol. 255:188-192.
Flück, P., Hyndman, R. D., Rogers, G. C., and Wang, K., 1997. Three-Dimensional Dislocation Model for Great Earthquakes of the Cascadia Subduction Zone, Journal of Geophysical Research, vol. 102: 20,539-20,550.
Garrison-Laney, C. G., 1998. Diatom Evidence for Tsunami Inundation from Lagoon Creek, a Coastal Freshwater Pond, Del Norte County, California: M. S. thesis, Arcata, California, Humboldt State University, 56 p.
Haugerud, R. A., 1999. Digital elevation model (DEM) of Cascadia, latitude 39N – 53N, longitude 116W – 133W, United States Geological Survey Open-File Report 99-369.
Heaton, f f., Kanamori, F. F., 1984. Seismic Potential Associated with Subduction in the Northwest United States, Bulletin of the Seismological Society of America, vol. 74: 933-941.
Hemphill-Haley, E., 1995. Diatom evidence for earthquake-induced subsidence and tsunami 300 yr ago in southern coastal Washington, Geological Society of America Bulletin, vol. 107: 367-378.
Hyndman, R. D., and Wang, K., 1995. The rupture zone of Cascadia great earthquakes from current deformation and the thermal regime, Journal of Geophysical Research, vol. 100: 22,133-22,154.
Jacoby, G. C., 1994. Tree-ring Dating of Coseismic Coastal Subsidence in the Pacific Northwest Region, United States Geological Survey, award number 1434-94-G-2451: 1-11.
Jacoby, G., Carver, G., Wagner, W., 1995. Trees and herbs killed by an earthquake ~300 yr ago at Humboldt Bay, California, Geology, vol. 23: 77-80.
Jacoby, G., Bunker, D. E., and Benson, B. E., 1997. Tree-ring evidence for an A. D. 1700 Cascadia earthquake in Washington and northern Oregon, Geology, vol. 25: 999-1002.
Kelsey, H. M., Witter, R. C., and Hemphill-Haley, E., 2002. Plate-boundary earthquakes and tsunamis of the past 5,500 yr, Sixes River estuary, southern Oregon, Geological Society of America Bulletin, vol. 114: 298-314.
Leroy, Thomas H., 1999, Sand Dune Stratigraphy and Paleoseismicity of the North and South Spits of Humboldt Bay, Northern California: M.S. thesis,Arcata, California, Humboldt State University, Department of Geology, 37 p.
Li, Wen-Hao, 1992, Evidence for the late Holocene coseismic subsidence in the lower Eel River Valley, Humboldt County, northern California: an application of foraminiferal zonation to indicate tectonic submergence: M.S. thesis, Arcata, California, Humboldt State University, Department of Geology, 87 p.
Manhart, C. S., 1992, High-Resolution Foraminiferid Stratigraphy as Evidence for Rapid, Coseismic Subsidence: Preliminary results, in Carver, G. A., Burke. R. M. [eds.] Friends of the Pleistocene Field Guidebook, Humboldt State University, Department of Geology, Arcata, CA, 265 p.
McCalpin, J. P., 1996. Application of Paleoseismic Data to Seismic Hazard Assessment and Neotectonic Research, in McCalpin, J. P. [ed.] Paleoseisomology, Academic Press, San Diego, CA, 439-494.
McCormac, F. G., Reimer, P. J., Hogg, A. G., Higham, T. F. G., Baillie, M. G. L. Palmer, J., Stuiver, M., 2002. Radiocarbon, vol. 44: 641-651.
McLaughlin, R. McLaughlin, R.J., Ellen, S.D., Blake, M.C., Jayko, A.S., Irwin, W.P., Aalto, K.R., Carver, G.A., Clarke, S.H., Jr., Barnes, J.B., Cecil, J.D., Cyr, K.A., 2000 Geologic map of the Cape Mendocino, Eureka, Garberville, and southwestern part of the Hayfork 30 X 60 Quadrangles and Adjacent Offshore Area, Northern California United States Geological Survey, Miscellaneous Field Studies 2336, Digital Database, http://geopubs.wr.usgs.gov/map-mf/mf2336
McPherson, R. M., 1989. Seismicity and Focal Mechanisms Near Cape Mendocino, Northern California: 1974-1984: M. S. thesis, Arcata, California, Humboldt State University, 75 p.
Merritts, D and Bull, W. B., 1989. Interpreting Quaternary uplift rates at the Mendocino triple junction, northern California, from uplifted marine terraces, Geology, vol. 17: 1020 – 1024.
Nelson, A. R., 1992. Holocene Tidal-Marsh Stratigraphy in South-Central Oregon – Evidence for Localized Sudden Submergence in the Cascadia Subduction Zone, in Quaternary Coasts of the United States: Marine and Lacustrine Systems, Society for Sedimentary Geology Special Publication No. 48: 287-301.
Nelson, A. R., Kashima, K., 1993. Diatom Zonation in southern Oregon Tidal Marshes Relative to Vascular Plants, Foraminifera, and Sea Level, Journal of Coastal Research, vol. 9: 673-697.
Nelson, A. R., Atwater, B. F., Bobrowsky, P. T., Bradley, L-A., Clague, J. J., Carver, G. A., Darienzo, M. E., Grant, W. C., Krueger, H. W., Sparks, R., Stafford, T. W., and Stuiver, M., 1995. Radiocarbon evidence for extensive plate boundary rupture about 300 years ago at the Cascadia subduction zone, Letters to Nature, vol. 378: 371-374.
Nelson, A. L., Jennings, A. E., and Kashima, K., 1996a. An earthquake history derived from stratigraphic and microfossil evidence of relative sea-level change at Coos Bay, southern coastal Oregon, Geological Society of America Bulletin, vol. 108: 141-154.
Nelson, A. R., Shennan, I., and Long, A. J., 1996b. Identifying coseismic subsidence in tidal-wetland stratigraphic sequences at the Cascadia subduction zone of western North America, Journal of Geophysical Research, vol. 101: 6115-6135.
Nelson, A. R., Ota, Y., Umitsu, M., Kashima, K., and Matsushima, Y., 1998. Seismic of hydrodynamic control of rapid late-Holocene sea-level rises in southern coastal Oregon, USA?, The Holocene, vol. 8: 287-299.
National Oceanographic and Atmospheric Administration, NOAA, 2000. Gill, S. K. and Schultz, J. R., [eds.] Tidal Datums and Their Applications, NOAA Special Publication NOS CO-OPS 1, U. S. Department of Commerce, National Ocean Service, Center for Operational Oceanographic Products and Services, Silver Spring, Maryland, 115 p.
Ogle, B. A., 1953. Geology of the Eel River Valley Area, Humboldt County, California: Bulletin of the California Division of Mines, vol. 164, 128 p.
Peters, R., Jaffe, B., Peterson, C., Gelfenbaum, G., and Kelsey, H. M., 2001, An overview of tsunami deposits along the Cascadia margin, International Tsunami Symposium Proceedings, Session 3, no. 3-3: 479-490.
Plafker, G., 1972, Alaska Earthquake pf 1964 and Chilean Earthquake of 1960: Implications for Arc Tectonics, Journal of Geophysical Research, vol. 77, no. 5: 901-925.
Satake, K., Shimazaki, K., Tsuki, Y., and Ueda, K., 1996, Time and size of a giant earthquake in Cascadia inferred from Japanese tsunami records of January 1700, Nature, vol. 379: 246-249.
Shapiro and Associates, (1980). Humboldt Bay Wetlands Review and Baylands Analysis, Report to Army Corps of Engineers, Vol. 1, 2, and 3.
Smith, S. W., Knapp, J. S., and McPherson, R. M., 1993, Seismicity of the Gorda Plate, Structure of the Continental Margin, and an Eastward Jump of the Mendocino Triple Junction, Journal of Geophysical Research, vol. 98: 8,153-8,171.
Stein, R. S., Marshall, G. A., and Murray, M. H., 1993. Permanent Ground Movement Associated with the 1992 M=7 Cape Mendocino, California, Earthquake: Implications for Damage to Infrastructure and Hazards to Navigation. United States Geological Survey Open-File Report 93-383, 44 p.
Stuiver, M., and Polach, H., A., 1977, Discussion: Reporting of 14C Data, Radiocarbon, vol. 19: 355-363.
Stuiver, M., and Reimer, P. J., 1986, A computer program for radiocarbon age calibration, Radiocarbon, vol. 28:1022-1030.
Stuiver, M., and Reimer, P. J., 1993, Extended 14C database and revised CALIB radiocarbon calibration program, Radiocarbon, vol. 35:215-230.
Stuiver, M., Reimer, P.J., Bard, E., Beck, J.W., Burr, G.S., Hughen, K.A., Kromer, B., McCormac, F.G., v. d. Plicht, J., and Spurk, M., 1998a. INTCAL98 Radiocarbon age calibration 24,000 – 0 cal BP, Radiocarbon, vol. 40:1041-1083.
Stuiver, M., Reimer, P.J., and Braziunas, T. F. 1998b. High-precision radiocarbon age calibration for terrestrial and marine samples, Radiocarbon, vol. 40:1127-1151.
Valentine, D. W., 1992, Late Holocene Stratigraphy, Humboldt Bay, California: Evidence for Late Holocene Paleoseismicity of the Southern Cascadia Subduction Zone: M.S. thesis, Arcata, California, Humboldt State University, 82 p.
Vick, G., 1988, Late Holocene Paleoseismicity and relative vertical crustal movements, Mad River Slough, Humboldt Bay, California: M.S. thesis, Arcata, California, Humboldt State University, 88 p.
Williams, T. B., 2003, The Geodetic Signature of Modern Deformation (1993-2002) Within the Southern Cascadia Margin, Northwestern California: M.S. thesis, Arcata, California, Humboldt State University, 88 p.
Witter, R.C., 1999. Late Holocene Paleoseismicity, Tsunamis and Relative Sea-Level Changes Along the South-Central Cascadia Subduction Zone, Southern Oregon, U.S.A. PhD. Dissertation: University of Oregon, Department of Geological Sciences, 152 p., plus appendices.
Witter, R. C., Patton, J. R., Carver, G. C., Kelsey, H. M., Garrison-Laney, C., Koehler, R. D., and Hemphill-Haley, E., 2002. Final Technical Report: Upper Plate Earthquakes on the Western Little Salmon Fault and Contemporaneous Subsidence of Southern Humboldt Bay over the past 3,600 Years, Northwestern California. United States Geological Survey, National Earthquake Hazards Reduction Program, Award No. 01HQGR0215, 37 p.
Witter, R. C., Kelsey, H. M., and Hemphill-Haley, 2003, Great Cascadia earthquakes and tsunamis of the past 6700 years, Coquille River estuary, southern coastal Oregon, Geological Society of America Bulletin, vol. 115: 1289-1306.
Yamaguchi, D. K., Atwater, B. F., Bunker, D. E., Benson, B. E., Reid, M. S., 1997. Tree-ring dating the 1700 Cascadia earthquake, Nature, vol. 389: 922.