Western limits of the Seattle fault zone and its interaction with the Olympic Peninsula, Washington

Lamb, Andrew P.; Liberty, Lee M.; Blakely, Richard J.; Pratt, Thomas L.; Sherrod, Brian L.; Wijk, Kasper van

doi:10.1130/ges00780.1

Cited by 16 publications

(14 citation statements)

References 54 publications

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“…We also examined inferred structures, such as the Olympic Wallowa Lineament [ Raisz , ], proposed to connect thrust faulting between the Yakima Fold and Thrust Belt (YFTB) and the Puget Lowland [ Blakely et al ., ]. In Puget Sound and the Strait of Juan de Fuca we include faults inferred from high‐resolution seismic reflection profiling [ Mace and Keranen , ; Lamb et al ., ; Barrie and Greene , ] and from aeromagnetic lineations [ Mace and Keranen , ].…”

Section: Approachmentioning

confidence: 99%

“…Near the Puget Lowland, several segments of strike‐slip structures are closely aligned with small circle paths. These include segments of the Hood Canal fault, the Carr Inlet lineation, the DeWatto fault inferred from potential field geophysical anomalies [ Lamb et al ., ], a tear fault in the Seattle fault, and the western Rattlesnake Mountain fault (Figures and ). We informally use the name Carr Inlet lineation, for a lineation defined by a number of deep crustal (20–35 km) right‐lateral focal mechanisms along the eastern end of the Tacoma fault (Figure ).…”

Section: Geologic Pole Of Rotation Defined By Strike‐slip Faults and mentioning

confidence: 99%

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Evidence for distributed clockwise rotation of the crust in the northwestern United States from fault geometries and focal mechanisms

et al. 2017

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Paleomagnetic and GPS data indicate that Washington and Oregon have rotated clockwise for the past 16 Myr. Late Cenozoic and Quaternary fault geometries, seismicity lineaments, and focal mechanisms provide evidence that this rotation is accommodated by north directed thrusting and right‐lateral strike‐slip faulting in Washington, and SW to W directed normal faulting and right‐lateral strike‐slip faulting to the east. Several curvilinear NW to NNW trending high‐angle strike‐slip faults and seismicity lineaments in Washington and NW Oregon define a geologic pole (117.7°W, 47.9°N) of rotation relative to North America. Many faults and focal mechanisms throughout northwestern U.S. and southwestern British Columbia have orientations consistent with this geologic pole as do GPS surface velocities corrected for elastic Cascadia subduction zone coupling. Large Quaternary normal faults radial to the geologic pole, which appear to accommodate crustal rotation via crustal extension, are widespread and can be found along the Lewis and Clark zone in Montana, within the Centennial fault system north of the Snake River Plain in Idaho and Montana, to the west of the Wasatch Front in Utah, and within the northern Basin and Range in Oregon and Nevada. Distributed strike‐slip faults are most prominent in western Washington and Oregon and may serve to transfer slip between faults throughout the northwestern U.S.

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Section: Approachmentioning

confidence: 99%

Section: Geologic Pole Of Rotation Defined By Strike‐slip Faults and mentioning

confidence: 99%

Evidence for distributed clockwise rotation of the crust in the northwestern United States from fault geometries and focal mechanisms

et al. 2017

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“…Most of what is known about the subsurface structure beneath the Puget Lowland comes from potential field surveys and seismic studies (Figs. 1B, 1C; e.g., Daneš et al, 1965, Gower et al, 1985Finn, 1990;Finn et al, 1991;Johnson et al, 1994Johnson et al, , 1999Snavely and Wells, 1996;Pratt et al, 1997;Brocher et al, 2001Brocher et al, , 2004Blakely et al, 2011;Lamb et al, 2012;Mace and Keranen, 2012). In the Puget Lowland region, these geophysical data indicate that north-south compression has deformed the forearc basement and overlying Quaternary and older rocks into a series of fault-or fold-bounded basins and uplifts (e.g., Gower et al, 1985;Pratt et al, 1997;Brocher et al, 2001;Van Wagoner et al, 2002;Kelsey et al, 2008;Liberty and Pratt, 2008;Blakely et al, 2009;Mace and Keranen, 2012).…”

Section: Geological and Geophysical Backgroundmentioning

confidence: 99%

Shallow geophysical imaging of the Olympia anomaly: An enigmatic structure in the southern Puget Lowland, Washington State

et al. 2016

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Gravity and magnetic anomalies suggest that the Olympia structure beneath the southern Puget Lowland (western Washington State, U.S.) vertically displaces Eocene Crescent Formation strata. Northeast of the Olympia structure, middle Eocene Crescent Formation is beneath 4-6 km of Paleogene-Neogene and Quaternary strata of the Tacoma basin, whereas the Crescent Formation is exposed at the surface immediately to the south. Although numerous marine seismic reflection profiles have been acquired near the surface location of the Olympia structure as defined by potential field anomalies, its tectonic character remains enigmatic, in part because inlets of southern Puget Sound are too shallow for the collection of deep-penetration marine seismic profiles across the geophysical anomalies. To supplement existing shallow-marine data near the structure, we acquired 14.6 km of land-based seismic reflection data along a profile that extends from Crescent Formation exposed in the Black Hills northward across the projected surface location of the Olympia structure. The reflection seismic data image the Crescent bedrock surface to ~1 km depth beneath the southern Tacoma basin and reveal the dip on this surface to be no greater than ~10°. Although regional potential field data show a strong linear trend for the Olympia structure that implies folding over a blind thrust and/or bedrock juxtaposed against a weakly to nonmagnetic sediment section, high-resolution magnetic anomaly analysis along the land-based profile suggests that the structure is more complex. Overall, seismic and potential-field profiles presented in this study identify only minor shallow faulting within the projected surface location of the Olympia structure. We suggest that the mapped trace of the Olympia structure along the northern flank of the Black Hills, at least within the study area, is constrained by juxtaposed normal and reversely magnetized Crescent Formation units and minor tectonic deformation of Crescent Formation bedrock. Black Hills Uplift and the Olympia Structure The Black Hills are one of the largest uplifted exposures of basement rocks in the area surrounding the Puget Lowland. Uplift began in the early or middle Eocene, based on the stratigraphic relationship between onlapping latest Eocene to Oligocene sediments on the west and south sides of the Black Hills and evidence for the influence of an uplifted Black Hills on basin sedimentation GEOSPHERE

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“…Although the lateral extent and geometry of the fault zone are still subjects of active debate among the local geophysical and geological community (e.g. ten Brink et al 2006;Arcos 2012b;Lamb et al 2012), the seismic potential of the fault was firmly established in 1992 with the publication of five coordinated articles in Science. The evidence presented for fault movement comprised an abrupt uplift of 7 m at Restoration Point on the south side of the fault, up to 1 m of subsidence to the north of the fault, contemporaneous rock avalanches in the Olympic Mountains, landslides into Lake Washington, and tsunami deposits up to 40 km away from the fault zone (Atwater and Moore 1992;Bucknam et al 1992;Jacoby et al 1992;Karlin and Abella 1992;Schuster et al 1992).…”

Section: Geological Evidence Of Late Holocene Seismicitymentioning

confidence: 99%

“…Arcos (2012a) cautions, however, that the beach berm may not simply be a product of tectonic uplift. Another candidate, and the most likely, is the Saddle Mountain deformation zone, which lies about 15 km northwest of the Skokomish River delta, and may accommodate north-south compression on the western edge of the Seattle uplift (Lamb et al 2012).…”

Section: Geological Evidence Of Late Holocene Seismicitymentioning

confidence: 99%

Geoarchaeological Perspectives on the “Millennial Series” of Earthquakes in the Southern Puget Lowland, Washington, USA

Hutchinson¹

2015

Radiocarbon

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Surface-breaking ruptures on shallow crustal faults in the southern Puget Lowland in western Washington State about a millennium ago prompted abrupt changes in land level and triggered tsunamis in Puget Sound. The displacement on the Seattle fault most likely occurred in the 1050–1020 cal BP interval. Structures further south (the Tacoma and Olympia faults, and one or more faults in the southern Hood Canal zone) ruptured at about the same time, or slightly earlier. The low frequency of radiocarbon ages from archaeological sites in the region in the aftermath of the “millennial series” of earthquakes, when compared to bootstrapped samples from a database of 1255 ages from the Pacific Northwest as a whole, suggests that these very large earthquakes had significant socioeconomic consequences. The cultural record from coastal archaeological sites shows that although survivors camped on the shore in the aftermath, many coastal villages appear to have been abandoned, and were not reoccupied for several centuries. There is little evidence, however, to suggest that people migrated from southern Puget Sound to neighboring areas, and no evidence of social conflict in the adjacent areas that might have served as havens.

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Western limits of the Seattle fault zone and its interaction with the Olympic Peninsula, Washington

Cited by 16 publications

References 54 publications

Evidence for distributed clockwise rotation of the crust in the northwestern United States from fault geometries and focal mechanisms

Evidence for distributed clockwise rotation of the crust in the northwestern United States from fault geometries and focal mechanisms

Shallow geophysical imaging of the Olympia anomaly: An enigmatic structure in the southern Puget Lowland, Washington State

Geoarchaeological Perspectives on the “Millennial Series” of Earthquakes in the Southern Puget Lowland, Washington, USA

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