A Coast Range Boundary Fault (CRBF, discussed above) was inferred on the basis of differences in the basement rock to the west and east of Puget Sound (the Crescent FormationCascadia core contact), and arbitrarily mapped at various locations including Lake Washington; north of the OWL this is now generally identified, with the Southern Whidbey Island Fault. [130] This is likely not coincidental, as it appears that the Tacoma and Seattle faults converge at depth (see diagram above) in a way that northsouth compression tends to force the Seattle Uplift up, resulting in dip-slip movement on both fault zones. Even before Washington became a state in 1889, Puget Sound beaches had been exploited as log dumps, farmed for shellfish, occupied as homesites and enjoyed for recreation. [173] One reason for caution is that a detailed gravity survey was unable to resolve whether the Olympia structure is, or is not, a fault. Tsunami waves would reach Seattle within minutes after earthquake The true length of the UPF is likely twice as long, as it forms the southern margin of an aeromagnetic high that extends another 25km to the southeast. Puget Sound and San Juan islands. [213] Seismicity sometimes occurs in zones, such as has been observed under Mercer Island, or from downtown Seattle towards Kirkland[214] but whether particular zones reflect undiscovered faults, or might be the source of damaging earthquakes, is generally unknown. The Canyon River Fault is believed to have caused a similar-sized earthquake less than 2,000 years ago;[167] this is a particular hazard to the Wynoochee Dam (to the west). 3511 NE Second St. Renton, WA 98056. South of the OWL a definite eastern boundary has not been found, with some indications it is indefinite. 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. (Links with more information on various hazards can be found at Seattle Fault.). Active tectonics of the Seattle fault and central Puget sound [73] The presence of detritus from the Idaho Batholith[72] indicates a former location closer to southern Idaho. - Read More Expert Puts Turkey, Syria Quake into Perspective | FOX 13 [61], North of Everett is an area of parallel ridges and stream drainages oriented approximately NW-SE, evident even on non-geological maps. [29] This prospect is especially intriguing as a possible explanation of a cluster of seismic events around 1100 years ago.[30]. It has been suggested that a corresponding change in the character of the SWIF may reflect a change in the direction of regional crustal strain. "Most often, when we think of tsunamis, we think of our outer coast and communities along the Pacific Ocean. The WRZ and SHZ are associated with the southern Washington Cascades conductor (SWCC), a formation of enhanced electrical conductivity[194] lying roughly between Riffe Lake and Mounts St. Helens, Adams, and Rainier, with a lobe extending north (outlined in yellow, right). It is not notably seismogenic. [49] Yet it is also notable that "most seismicity in the northern Puget Sound occurs along and southwest of the southern Whidbey Island fault at typical depths of 1527 km within the lower part of the Crescent Formation. Read More. [199] It has been speculated that the SHZ might extend under the Kitsap Peninsula (central Puget Sound), possibly involved with a section of the subducting Juan de Fuca plate that is suspected of being stuck. The alternative, that younger faulting in the Rogers Belt has offset the DMF Cheney argued that the MVF had offset the DMF 47km. [69] The principal zone of faulting extends from the Woods Creek Fault to the Granite Falls Fault Zone (GFFZ), slightly offset from the WCF and running under the town of Granite Falls. [46] Seismic tomography studies show that this portion of the SWIF marks a strong contrast of seismic velocities, such as is expected of Crescent Formation basalts in contact with the metamorphic basement rocks of the Cascades geologic province to the east. Contact Us | VA Puget Sound Health Care | Veterans Affairs [Paper No. 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? [192] Indeed, it is mainly by their seismicity that these faults are known and have been located, neither showing any surface faulting. Fault lines in the New Madrid seismic zone are being mapped, thanks in part to . [38] These earthquakes probably caused tsunamis, and several nearby locations have evidence of tsunamis not correlated with other known quakes. [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). [39] On the basis of marine seismic reflection surveying in the Strait of Juan de Fuca it has been suggested that the DMF, SPF, and UPF are structurally connected (at least in the segment crossing Whidbey Island). [154] In this view Hood Canal is only a syncline (dip) between the Olympic Mountains and the Puget Lowland, and such faults as have been found there are local and discontinuous, ancillary to the main zone of faulting to the west. But the western segment the Devils Mountain Fault has left-lateral movement. . normal. Extensive research has since shown the Seattle Fault to be part of a regional system of faults . [85] The Tokul Creek Fault (TCF) strikes NNE from Snoqualmie, aligned with a possible offset of the Western Melange Belt[86] and with a valley that cuts through to the Skykomish River; it is now believed to be of regional significance. [21] The OWL appears to be a deep-seated structure over which the shallower crust of the Puget Lowland is being pushed, but this remains speculative. In the angle between these is located the minor Lincoln Creek uplift, the Doty Hills, and, further west, an impressive chunk of Crescent basalt. Estimated shaking in the Puget Sound - Strange Sounds If entirely analogous, then "roof duplex" might also apply, and the Olympia Fault would be a reverse fault similar to the Tacoma Fault. Recent EQ List It's the other counties in the Puget . Discovery of faults has been greatly facilitated with the development of LIDAR, a technique that can generally penetrate forest canopy and vegetation to image the actual ground surface with an unprecedented accuracy of approximately one foot (30cm). [19] These terranes were covered by the basalts of the Crescent Formation (part of Siletzia). UW researchers model tsunami hazards on the Northwest coast This forms a pocket or trough what one local geologist calls the "big hole between the mountains"[17] between the Cascades on the east and the Olympic Mountains and Willapa Hills on the west. The Cascadia Fault is 620 miles long off the coast of Washington and British Columbia. The map also shows potentially active faults from a separate 2014 report (click here to download). Though the Olympia Structure (a suspected fault) runs towards the SHZ, and delineates the northern edge of an exposed section of the Crescent Formation, it appears to be an upper crustal fold, part of a pattern of folding that extends southeast to cross the Columbia River near The Dalles, and unrelated to the mid and lower crustal SHZ. The passive roof duplex model of Brocher et al. Although Washington State's Puget Sound has been shaken every few decades, damage in the region's largest cities, including Seattle, Tacoma and Olympia, has only ever been modest. Its capable magnitude is a megathrust quake exceeding 9.0. Geologic map of southwestern Washington (GM-34). Though these faults have been traced for only a little ways, the southeast striking anticlines they are associated with continue as far as Riffe Lake, near Mossyrock. Olympic Peninsula, Washington has had: (M1.5 or greater) 0 earthquakes in the past 24 hours. In particular, to the southeast of Mount St. Helens and Mount Rainier they reflect a regional pattern of NNW oriented faulting, including the Entiat Fault in the North Cascades and the Portland Hills and related faults around Portland (see QFFDB fault map). 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). These are usually fairly short, and not believed to be significantly seismogenic. ), The Coast Range Boundary Fault (CRBF) is hypothesized, expected on the basis of tectonic considerations, which may correlate in part with one or more currently known faults, or may involve as yet undiscovered faulting. One problem with this is that the parts of the SWIF east of Puget Sound do not show the velocity contrasts that would indicate contrasting rock types. Prior to 2000, prominent aeromagnetic anomalies strongly suggested that the fault zone continued southeast, perhaps as far as the town of Duvall, but this was uncertain as the SWIF is largely concealed, and the faint surface traces generally obliterated by urban development.