[76], The Cherry Creek fault zone (CCFZ) was discovered in 2010 while mapping the area at the north end of the Rattlesnake Mountain fault zone (RMFZ). See Snavely et al. Thick glacial and other deposits, heavy vegetation, urban development, and a topography of sharp relief and rapid erosion obscures the surface expression of faults in this region, and has hindered their discovery. Folding and faulting has exposed these basalts in some places (black areas in diagram); the intervening basins have been filled by various sedimentary formations, some of which have been subsequently uplifted. Combined with continued aggressive electric conservation efforts, Energize . [43] Just south of Victoria, British Columbia it intersects the west-striking Devils Mountain Fault (reviewed above), and either merges with it,[44] or crosses (and possibly truncates) it to connect with the Leech River Fault. [131], The Tacoma Fault was first identified by Gower, Yount & Crosson (1985) as a gravitational anomaly ("structure K") running east across the northern tip of Case and Carr Inlets, then southeast under Commencement Bay and towards the town of Puyallup. The western flank of the Seattle Uplift forms a strong gravitational, aeromagnetic, and seismic velocity gradient known as the Dewatto lineament. The implications of this are not only "the possibility of a moderate to large crustal earthquake along the SHZ", but that the tectonics under Puget Sound are more complicated than yet understood, and may involve differences in the regional stress patterns not reflected in current earthquake hazard assessments. These faults are: the Kopiah Fault (note the curious curve), Newaukum Fault, Coal Creek Fault, and three other unnamed faults. This is supported by geologically recent scarps and other signs of active faulting on the Saddle Mountain faults, and also discovery of a geophysical lineament running through Pleasant Harbor (south of Brinnon) that appears to truncate strands of the Seattle Fault. South of Monroe the folds of the Rogers Belt are obscured by subsequent volcanic formations, but other faults parallel to the RMFZ (e.g., the Snoqualmie Valley and Johnson's Swamp fault zones) extend the general trend of NNW faulting as far as Monroe. Puget Sound Lidar Consortium Finding faults scarp(n). But today, after 131 years of statehood, residents of this region still don't know if they have a legal right to walk across a privately . [16] For the past 50 million years or so (since the early Eocene epoch) these have been thrust by subduction up against the North Cascades ("fixed block" in the diagram), which sit on the North American Plate. [132], Scarps associated with Holocene uplift of the Tacoma fault have been traced westward to Prickett Lake (southwest of Belfair, see map). When the applied stresses become overpowering, the rocks at the fault rupture. These faults are not quite aligned with the Olympia structure, striking N75W (285) rather than N45W (315). There are some interesting relationships here. [195] The southwestern boundary of the SWCC, where it is believed to be in near vertical contact with the Eocene basalts of the Crescent Formation, forms a good part of the 90km (56 mile) long SHZ. This interpretation suggests that the Seattle Uplift acts as a rigid block, and possibly explains the kinematic linkage by which large earthquakes may involve ruptures on multiple faults: the Seattle, Dewatto, and Tacoma faults represent the northern, western, and southern faces of a single block. [103] Other seismic tomography has tantalizingly suggested three north-striking strands under Seattle, and a fourth just east of Lake Washington. Curiously, the extension of line "B" north of the OWL is approximately the eastern limit of Puget Sound seismicity, the rest of southwestern Washington and the North Cascades being relatively aseismic (see the seismicity map, above). [215] According to the Washington state Department of Natural Resources, more than 1,000 earthquakes happen in Washington state each year! [114] An early view was that "the Seattle Fault appears to be truncated by the Hood Canal fault and does not extend into the Olympic Mountains". About 1,100 years ago, a major earthquake rocked Puget Sound, suddenly shooting what is now Restoration Point on Bainbridge Island up about 23 feet while Seattle 's West Point sunk more than. ), Aeromagnetic mapping in 1999 showed a very prominent anomaly[172] (such as typically indicates a contrast of rock type); that, along with paleoseismological evidence of a major Holocene earthquake, has led to a suggestion that this structure "may be associated with faulting". [180], That Olympia and the south Sound are at risk of major earthquakes is shown by evidence of subsidence at several locations in southern Puget Sound some 1100 years ago. The energy of the somewhat smaller Benioff earthquakes is likewise diluted over a relatively large area. The Seattle uplift, and possibly the Black Hills uplift, consist of Crescent Formation basalt that was exposed when it was forced up a ramp of some kind. This formation, up to 15km thick, is largely buried (from one to ten kilometers deep), and known mainly by magnetotellurics and other geophysical methods. fault Which of the following statements best describes elastic-rebound theory? These lineaments have been associated with possible zones of faulting in the crust and subducting plate.[212]. Detailed mapping of this area since 2006 has revealed a complex pattern of faults. The 1949, 1965, and 2001 Puget Sound earthquakes were the result of _____ fault movement within the Juan de Fuca plate. In the wedge model of Pratt et al. This is just after the terrane carrying the Olympic Mountains came into contact with the North American continent. It appears that the Seattle Uplift is acting as a rigid block, with the Tacoma, Dewatto, and Seattle faults being the southern, western, and northern faces. The largest intra-crustal earthquakes have about the same total energy (which is about one-hundredth of a subduction event), but since they are closer to the surface they will cause more powerful shaking, and, therefore, more damage. This is a seemingly accidental alignment of topographic features that runs roughly east-southeast from the north side of the Olympic Peninsula to the Wallowa Mountains in northeastern Oregon. These faults also form the north and south boundaries of uplifted pre-Tertiary rock, suggesting that the faults come together at a lower level, much like one model of the Seattle and Tacoma faults, but at a smaller scale. Most of these "faults" are actually zones of complex faulting at the boundaries between sedimentary basins (synclines, "") and crustal uplifts (anticlines, ""). The earthquake scenario used in the modeling is a "very large, low-probability" magnitude 7.5 earthquake on the Seattle Fault, which runs east-west through Puget Sound and downtown Seattle.. Initially it was not specified, and rather vaguely indicated to be west of Restoration Point (i.e., west of Puget Sound). Mount Vernon Fault/Granite Falls FZ/Woods Creek, Rogers Belt (Mount Vernon Fault/Granite Falls Fault Zone), Saint Helens Zone and Western Rainier Zone, Quaternary fault and fold database (QFFDB), USGS QFFDB Fault #574, Devils Mountain Fault, USGS QFFDB Fault #571, Strawberry Point Fault, USGS QFFDB Fault #573, Utsalady Point Fault, Brightwater regional sewage treatment plant, USGS QFFDB Fault #572, Southern Whidbey Island Fault, USGS QFFDB Fault #575, Saddle Mountain Faults, "A Rifted Margin Origin for the Crescent Basalts and Related Rocks in the Northern Coast Range Volcanic Province, Washington and British Columbia", "Preliminary atlas of active shallow tectonic deformation in the Puget Lowland, Washington", "Volcanism, Isostatic Residual Gravity, and Regional Tectonic Setting of the Cascade Volcanic Province", "Findings on the southern Whidbey Island fault zone from aeromagnetic anomalies, lidar surveys, and trenching", "The Saddle Mountain Fault Deformation Zone, Olympic Peninsula, Washington: Western Boundary of the Seattle Uplift", "Connecting Crustal Faults and Tectonics from Puget Sound across the Cascade Range to the Yakima Fold and Thrust Belt, Washington: Evidence from New High-Resolution Aeromagnetic Data [Abstract GP232-02]", Eos, Transactions, American Geophysical Union, "The Cottage Lake Aeromagnetic Lineament: A possible onshore extension of the Southern Whidbey Island Fault, Washington", "Location, structure, and seismicity of the Seattle fault zone, Washington: Evidence from aeromagnetic anomalies, geologic mapping, and seismic-reflection data", 10.1130/0016-7606(2002)114<0169:LSASOT>2.0.CO;2, "High-pressure metamporphism and uplift of the Olympic subduction complex", 10.1130/0091-7613(1990)018<1252:HPMAUO>2.3.CO;2, "Interpretation of the Seattle Uplift, Washington, as a Passive-Roof Duplex", "Tectonic elements and evolution of northwest Washington", "Quaternary faulting on Dow Mountain, Mason County", "Major Cenozoic faults in the northern Puget Lowland of Washington", "High-Resolution Seismic Reflection Imaging of Growth Folding and Shallow Faults beneath the Southern Puget Lowland, Washington State", "LITHOPROBE southern Vancouver Island: Cenozoic subduction complex imaged by deep seismic reflections", "Geologic map of the Lilliwaup 7.5-minute quadrangle, Mason County, Washington", "Geologic map of the Holly 7.5-minute quadrangle, Jefferson, Kitsap, and Mason Counties, Washington", "Geologic map of the Eldon 7.5-minute quadrangle, Jefferson, Kitsap, and Mason Counties, Washington", "Geophysical Investigation of the Southern Puget Sound Area, Washington", "Geologic Map and Interpreted Geologic History of the Bow and Alger 7.5-minute Quadrangles, Western Skagit County, Washington", "Geologic Map of Washington Northwest Quadrant", "Geologic map of the Oak Harbor, Crescent Harbor, and part of the Smith Island 7.5-minute quadrangles, Island County", "Geologic map of the McMurray 7.5-minute Quadrangle, Skagit and Snohomish Counties, Washington, with a Discussion of the Evidence for Holocene Activity on the DarringtonDevils Mountain Fault Zone", "Geologic map of the Fall City 7.5-minute quadrangle, King County, Washington", "Geologic map of the North Bend 7.5-minute quadrangle, King County, Washington, with a discussion of major faults, folds, and basins in the map area", "Geologic Map of the Snoqualmie 7.5-Minute Quadrangle, King County, Washington", "Geologic map of the Carnation 7.5-minute quadrangle, King County, Washington", "Supplement to the geologic map of the Carnation 7.5-minute quadrangle, King County, Washington Geochronologic, geochemical, point count, geophysical, earthquake, fault, and neotectonic data", "Geologic map of the Monroe 7.5-minute quadrangle, King County, Washington", "Geologic map of the Lake Joy 7.5-minute quadrangle, King County, Washington", "Geologic map of the Sultan 7.5-minute quadrangle, Snohomish and King Counties, Washington", "Geologic Map of the Lake Chaplain 7.5-minute Quadrangle, Snohomish County, Washington", "Geologic map of the Lake Roesiger 7.5-minute quadrangle, Snohomish County, Washington", "Geologic Map of the Granite Falls 7.5-minute Quadrangle, Snohomish County, Washington", "Imaging Crustal Structure in Southwestern Washington With Small Magnetometer Arrays", "Geology of the Mount St. Helens Area: Record of Discontinuous Volcanic and Plutonic Activity in the Cascade Arc of Southern Washington", "Geophysical constraints on Washington convergent margin structure", "Aeromagnetic map compilation: procedures for merging and an example from Washington", "Something old, something new, something borrowed, something blue - a new perspective on seismic hazards in Washington using aeromagnetic data", "Constraints on surface deformation in the Seattle, WA, urban corridor from satellite radar interferometry time-series analysis", "Crustal Structure and Earthquake Hazards of the Subduction Zone in Southwestern British Columbia and Western Washington", "Late Mesozoic or Early Tertiary Melanges in the Western Cascades of Washington", "Seismotectonic map of the Puget Sound region, Washington", "Distribution of late Cenozoic volcanic vents in the Cascade Range: Volcanic arc segmentation and regional tectonic considerations", "Geologic map of the Wildcat Lake 7.5' quadrangle, Kitsap and Mason Counties, Washington", "Fault scarp detection beneath dense vegetation cover: airborne LIDAR mapping of the Seattle Fault Zone, Bainbridge Island, Washington State", 10.1130/1052-5173(2003)13<0004:HLTOTP>2.0.CO;2, "Structural variation along the Devil's Mountain fault zone, northwestern Washington", 10.1130/0091-7613(1980)8<15:SOTCVC>2.0.CO;2, "Fault number 572, Southern Whidbey Island Fault", "Active shortening of the Cascadia forearc and implications for seismic hazards of the Puget Lowland", "Active tectonics of the Seattle fault and central Puget Sound, Washington Implications for earthquake hazards", 10.1130/0016-7606(1999)111<1042:ATOTSF>2.3.CO;2, "Evidence for Late Holocene Earthquakes on the Utsalady Point Fault, Northern Puget Lowland, Washington", 10.1130/0091-7613(1994)022<0071:OAEOTS>2.3.CO;2, "The southern Whidbey Island fault An active structure in the Puget Lowland, Washington", 10.1130/0016-7606(1996)108<0334:TSWIFA>2.3.CO;2, "Late Holocene displacement on the Southern Whidbey Island fault zone, northern Puget lowland", "The Tahuya Lineament: Southwestern Extension of the Seattle Fault? How the CRBF might run north of Seattle (specifically, north of the OWL, which Seattle straddles) is unknown, and even questioned, as there is no direct evidence of such a fault. One animation shows the expected path of a Puget Sound tsunami generated by a quake on the Seattle Fault. [40], The Southern Whidbey Island Fault (SWIF) is a significant terrane boundary manifested as an approximately four mile wide zone of complex transpressional faulting with at least three strands. Part of the Snohomish River Delta between Everett and Marysville could get nearly 6 feet, and Seattle's Harbor Island could be inundated with nearly 4 feet of water. Those Hollywood depictions of a. Publication Year: 2010: Title: A magnitude 7.1 earthquake in the Tacoma Fault Zone A plausible scenario for the southern Puget Sound region, Washington: DOI: 10.3133/fs20103023: Authors: Base map is hillshaded DEM derived from LiDAR data (pixel size 1.8 m) from Puget Sound LiDAR Consortium; illumination from azimuth 05, at 5 above the horizon; datum is NAD83, UTM zone 10N. The SE striking Scammon Creek Fault seems to be terminated by the Salzer Creek Fault (the exact relationship is not clear), with the latter continuing east for another seven miles. The magnitude-4.0 earthquake that rattled people awake across the Puget Sound region last Wednesday probably struck on the western edge of the Seattle Fault, according to geologists. Not until 2001 was it identified as a fault zone,[12] and only in 2004 did trenching reveal Holocene activity.
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