In some places, such as along the South Fork of the Stillaguamish River between Arlington and Granite Falls, there are also contrasting geological contacts. The uplift and basin pattern is continued to the west and southwest by the Grays Harbor Basin, Willapa Hills Uplift, and Astoria Basin,[25] but it is not known if these are bounded by faults in the same manner as in the Puget Sound region. [37] Trenching on the UPF (at a scarp identified by LIDAR) shows at least one and probably two Holocene earthquakes of magnitude 6.7 or more, the most recent one between AD 1550 to 1850, and possibly triggered by the 1700 Cascadia earthquake. [61], North of Everett is an area of parallel ridges and stream drainages oriented approximately NW-SE, evident even on non-geological maps. [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". It does bound the north side of the Chehalis basin, but the south boundary of the Black Hills Uplift is more properly the southeast striking Scammon Creek Fault that converges with the DotySalzer Creek Fault just north of Chehalis. In this model the Tacoma fault zone is primarily the result of local adjustments as the slab bends upward at the bottom of the ramp. In 1870, as construction of the Northern Pacific began, Seattle numbered fewer than 1,200 souls. This map is useful in showing the location and approximate length of faults but does not provide the impact an earthquake from a fault could have on the area surrounding. Here, the Cherry Creek and Tokul Creek faults zones on the east side of the RMFZ are conjugate to the SWIF on the west side. [155] North of the Seattle Fault accommodation of regional movement may be along the northwest-striking Dabob Bay Fault Zone. [115] This seems reasonable enough, as Hood Canal is a prominent physiographic boundary between the Olympic Mountains and Puget Lowlands, and believed to be the location of a major fault. Based on this and geophysical anomalies it was inferred that there is a major, active strike-slip fault zone running from the south end of Hood Canal, up Dabob Bay, and continuing north on land. Shallow fault below Seattle went undiscovered for a millennium Not until 2001 was it identified as a fault zone,[12] and only in 2004 did trenching reveal Holocene activity. The Seattle Fault is the most studied of the regional faults, which has led to several models of its structure, which may also be relevant to other faults. It appears the entire DDMFZ and Leech River fault system was pushed onto the early continental margin from an original alignment along the OWL. KUOW Public Radio on Twitter: "A UW researcher says the fault line that 09 Feb 2023 03:01:00 UW researchers model tsunami hazards on the Northwest coast Earthquakes and Faults | WA - DNR [182], The Doty Fault the southernmost of the uplift-and-basin dividing faults reviewed here, and located just north of the Chehalis Basin is one of nearly a dozen faults mapped in the CentraliaChehalis coal district in 1958. [54], It has been suggested that the SWIF might extend past its intersection with the RMFZ (with only peripheral strands turning to join the RMFZ) to cross the Cascades and eventually merge with or cross the OlympicWallowa Lineament;[55] a study of regional features suggests such a pattern. A Massive Earthquake Is Coming to CascadiaAnd It Can't Be Stopped Some of these faults possibly developed in the Mesozoic, when these deposits were in the accretionary wedge;[72] the cross-cutting NE and NNE-striking faults that form the various basins resulted from a subsequent change to transtension. (Their model of the Black Hills Uplift is analogous with their "wedge" model of the Seattle Uplift, discussed above, but in the opposite direction. 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. [153] For these reasons this is now a questioned fault, and is indicated on the map as a dashed line. Plot. [145] This is conformable with some regional tectonic interpretations[146] that put a major terrane boundary between the Olympics and the Puget Lowland, and imply a connection (either via the Discovery Bay Fault, or closer to Port Townsend) to the various faults in the Strait of Juan de Fuca. These faults are: the Kopiah Fault (note the curious curve), Newaukum Fault, Coal Creek Fault, and three other unnamed faults. [28] Faults and folds may develop where the thrust sheet is being bent, or where the leading edge is thrust over softer, weaker sedimentary deposits, and breaks off and slumps. Also intersecting at Mount St. Helens is a NE (045) trending line (red) of Pleistocene (about 4 Ma) plug domes and a topographic lineament (followed in part by Highway 12). [125] While some coherency is developing, the story is not complete: identified faults do not yet account for much of the region's seismicity. NW-striking black lines are right-lateral bedrock faults thought to be subsidiary to Dar- rington-Devils Mountain fault zone (Dragovich and DeOme, 2006). Tacoma, WA. [91] The relationship between these two fault zones is not entirely clear. 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.. A Puget Sound Fault running down the center of Puget Sound (and Vashon Island) was once proposed,[220] but seems to have not been accepted by the geological community. 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. The Seattle fault isn't a single strand, but a zone of subterranean fractures that extends across Puget Sound, passing under Seattle and reaching as far east as Issaquah. The maps show slightly lower . Of great interest here is that both the northern lobe of the SWCC and the Carbon River anticline are aligned towards Tiger Mountain (an uplifted block of the Puget Group of sedimentary and volcanic deposits typical of the Puget Lowland) and the adjacent Raging River anticline (see map). [188] In the acute angle between these is located the minor Lincoln Creek uplift, the Doty Hills, and an impressive chunk of uplifted Crescent basalt (reddish area at west edge of the map). Strawberry Point and Utsalady Point faults, "The Puget Lowland is a north-south-trending structural basin that is flanked by Mesozoic and Tertiary rocks of the Cascade Range on the east and by Eocene rocks of the Olympic Mountains on the west. [71], These faults cut through the Western Mlange Belt (WMB; blue area in map), exposed from North Bend (on Interstate 90) to Mount Vernon. "Puget Sound and related inland marine waters, including all salt waters of the state of Washington inside the international boundary line between Washington and British Columbia, and lying east of the junction of the Pacific Ocean and the Strait of Juan de Fuca, and the rivers and streams draining to Puget Sound as mapped by water resource . The energy of the somewhat smaller Benioff earthquakes is likewise diluted over a relatively large area. Read More. [134] Most authors align it with the strong gravitational anomaly (which typically reflects where faulting has juxtaposed rock of different density) and topographical lineament down Commencement Bay. Especially as seismic reflection data[135] shows some faulting continuing east across Vashon Island and the East Passage of Puget Sound (the East Passage Zone, EPZ) towards Federal Way and an east-striking anticline. (1997) a slab of rock mainly basalts of the Crescent Formation about 20km thick is being pushed up a "master ramp" of deeper material; this forms the Seattle Uplift. Do you live in a natural-disaster danger zone? Check this Seattle map An informal consortium of regional agencies has coordinated LIDAR mapping of much of the central Puget Lowland, which has led to discovery of numerous fault scarps which are then investigated by trenching (paleoseismology). [87], Rattlesnake Mountain is a prominent NNW trending ridge just west of North Bend (about 25 miles east of Seattle). The 1949, 1965, and 2001 Puget Sound earthquakes were the result of _____ fault movement within the Juan de Fuca plate. 206-296-3830. 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. [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. South of the OWL a definite eastern boundary has not been found, with some indications it is indefinite. 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. According to the recent seismological studies, the Seattle Fault is believed to be a zone of thrust or reverse faults that strikes through Seattle in the densely populated Puget Lowland of western Washington (Johnson et al., 1999). [185] The prospect of a major earthquake on the Doty Fault poses a serious hazard to the entire Puget Sound region as it threatens vital economic lifelines: At Chehalis there is but a single freeway (Interstate 5) and a single rail line connecting the Puget Sound region with the rest of the west coast; the only alternate routes are very lengthy.[186]. There is evidence that the Tacoma Fault connects with the White River River Fault (WRF) via the EPZ and Federal Way, under the Muckleshoot Basin (see map),[137] and thence to the Naches River Fault. And since those models for the Seattle Fault were published, there've actually been many more Puget Sound faults discovered. Puget Sound Energy Maps and Records Non-Disclosure Agreement: (NDA ONLY) ko ru zh es vi hi: PSE Map Request Form and Non-Disclosure Agreement: 07/29/2022: [32] And it is suggested that the Great Seattle Quake of approximately 1,100 years ago, and other coseismic events in southern Puget Sound around that time, were a single event that affected this entire block, with a magnitude of around 8, possibly triggered by an earthquake deeper in the crust.[33]. [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. Simply put, the basement rock on the west side of Puget Sound does not match the basement rock on the east side. Bubbles of methane rising from seafloor in Puget Sound - Phys.org Geochemistry, Geophysics, Geosystems , 2021; 23 (1) DOI: 10.1029/2021GC010211 Cite This Page : [203] This line is the southernmost of a band of NE trending faults and topographical lineaments that extend from the Oregon coast into the North Cascades. [6] The first definite indications of most of these faults came from gravitational mapping in 1965,[7] and their likely existence noted on mapping in 1980 and 1985. [133] The Tacoma fault was initially suspected of following a weak magnetic anomaly west to the Frigid Creek fault,[127] but is now believed to connect with a steep gravitational, aeromagnetic, and seismic velocity gradient that strikes north towards Green Mountain (Blue Hills uplift). The geology also suggests that the DMF is moving obliquely up a ramp that rises to the east,[35] possibly an ancient coastal shore. Large plumes of methane bubbles have been discovered throughout the waters of Puget Sound prompting questions about the Puget Sound food web, studies of earthquake faults and climate-change research. [139] The Dewatto linement extends from the western end of the Tacoma fault (see map immediately above) northward towards Green Mountain at the western end of the Seattle fault. With inland, Puget Sound faults, like the Seattle Fault, the risk is comparatively smaller. Seattle Fault - Wikipedia The most striking concentrations of mid-crustal seismicity in western Washington outside of Puget Sound are the Saint Helens Zone (SHZ) and Western Rainier Zone (WRZ) at the southern edge of the Puget Lowland (see seismicity map, right). The Earthquake That Will Devastate the Pacific Northwest [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. These include (from north to south, see map) the: The Puget Sound region (Puget Lowland[1]) of western Washington contains the bulk of the population and economic assets of the state, and carries seven percent of the international trade of the United States. [47], To the southeast the SWIF passes through Admiralty Inlet (past Port Townsend) and across the southern part of Whidbey Island, crossing to the mainland between Mukilteo and Edmonds. 6 earthquakes in the past 7 days. This is because the Olympic terrane is moving (relative to North America) northeast; its continued clockwise rotation is akin to a giant wheel rolling up the western side of the North Cascade crystalline core. An earthquake occurs along a south-moving fault. 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). PSLC--finding faults - University of Washington [112] But if the Seattle Fault should break in conjunction with other faults (discussed above), considerably more energy would be released, on the order of ~M 8. [218] This would pose significantly greater seismic hazard than currently recognized, especially as the White River Fault is believed to connect with the Naches River Fault that extends along Highway 410 on the east side of the Cascades towards Yakima. [143] Such interconnection also suggests a capability for larger earthquakes (> M7 for the Seattle Fault); the amount of increased risk is unknown.[144]. Most of this thrust sheet consists of the Crescent Formation (corresponding to the Siletz River volcanics in Oregon and Metchosin Formation on Vancouver Island), a vast outpouring of volcanic basalt from the Eocene epoch (about 50 million years ago), with an origin variously attributed to a seamount chain, or continental margin rifting (see Siletzia). "Most often, when we think of tsunamis, we think of our outer coast and communities along the Pacific Ocean. They interpreted it as "simple folds in Eocene bedrock", though Sherrod (1998) saw sufficient similarity with the Seattle Fault to speculate that this is a thrust fault. The Pacific Northwest Seismic Network (PNSN) reported at least three earthquakes within the past few days. On the eastern side, where the SWCC is believed to be in contact with pre-Tertiary terranes accreted to the North American craton, matters are different. (E.g., the Olympia Fault is aligned with and appears to be the northernmost member of a set of faults between Olympia and Chehalis that may extend to the Columbia River, and there has been a suggestion that the Tacoma Fault may connect with the White RiverNaches River fault on the east side of the Cascades.[24]). The length of the Doty Fault is problematical: the report in 2000 gave it as 65km (40 miles), but without comment or citation. [74], Early Eocene igneous units in the area appear to be part of a 49- to 44- Ma magmatic belt that appeared just after the arrival of Siletzia, and possibly associated with that event. 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. The energy released depends on the length of the fault; the faults here are believed capable of generating earthquakes as great as M 6 or 7. A Cascadia event could cause dangerous currents in Puget Sound, reaching speeds up to 9 knots in the Agate Passage north of Bainbridge Island and 6 knots off of Discovery Park in Seattle. [216], An Everett Fault, running east-northeast along the bluffs between Mukilteo and Everett that is, east of the SWIF and at the southern edge of the Everett Basin has been claimed, but this does not appear to have been corroborated.[217]. [107], The Seattle Fault was first identified in 1965[108] but not documented as an active fault until 1992 with a set of five articles establishing that about 1100 years ago (AD 900930) an earthquake of magnitude 7+ uplifted Restoration Point and Alki Point, dropped West Point (the three white triangles in the Seattle Basin on the map), caused rockslides in the Olympics, landslides into Lake Washington, and a tsunami on Puget Sound. Saint Helens and Mt. 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. They are also on-strike with a swarm of faults on the Columbia River, bracketing The Dalles. Pratt et al. However, the SWCC is relatively shallow (no more than 15 km deep), and likely is draped over pre-Tertiary bedrock. It aligns with the West Coast fault and Queen Charlotte Fault system of strike-slip fault zones (similar to the San Andreas Fault in California) on the west side of Vancouver Island, but does not itself show any significant or through-going strike-slip movement. [119] Several studies show that the southernmost strand of the SF, once past Green Mountain, turns southwest, towards the Saddle Mountain and Frigid Creek faults. ), 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". (Enter only one word per blank.) Can be formed by differential erosion of adjacent hard and soft rock; by localized erosion, for example at the edge of a river terrace; by movement of a landslide; or by a shallow earthquake that is large enough to break the Earth's surface. Puget Sound Tsunami Simulation - National Oceanic and Atmospheric East of Puget Sound the basement of the Cascades province is various pre-Tertiary (older than 65 Ma) metamorphic rock. Black lines show the South Whidbey Island Fault Zone, the Seattle Fault Zone and the Tacoma Fault Zone. In the previous study seismicity, surface geology, and geophysical data were modeled in order to examine the fault structuring of the upper crust. Interpretation of the eastern part of the Tacoma Fault is not entirely settled. 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. The Little River Fault (see the QFFDB, Fault 556) is representative of an extensive zone of faults along the north side of the Olympic Peninsula and in the Strait of Juan de Fuca (likely connected with the fault systems at the south end of Vancouver Island, see fault database map), but these lie west of the crustal blocks that underlie the Puget Lowland, and again their possible impact on the Puget Sound region is unknown. While there is a bit of uplifted pre-Tertiary rock between the SPF and UPF, this does not truly fit the uplift and basin pattern described above because of the small scale (2km wide rather than around 20), and because the uplift here is entirely like a wedge being popped out between two nearly vertical faults, rather than being forced over a ramp such as is involved with the Seattle and Tacoma faults. The EPZ is active, being the locale of the 1995 M 5 Point Robinson earthquake.[136]. [198], Does the SHZ extend north? The structure of the Seattle Fault zone still have great uncertainty and there exist a number of interpretations. The Cascadia Fault is 620 miles long off the coast of Washington and British Columbia. One study of seismic vulnerability of bridges in the Seattle Tacoma area[4] estimated that an M 7 earthquake on the Seattle or Tacoma faults would cause nearly as much damage as a M 9 subduction earthquake. A Lofall Fault has been reported on the basis of marine seismic reflection surveying,[216] but has not been confirmed by trenching. 112 earthquakes in the past 365 days. Puget Sound Earthquake Faults - Seattle Earthquake Faults [183] While the towns of Centralia and Chehalis in rural Lewis County may seem distant (about 25 miles) from Puget Sound, this is still part of the Puget Lowland, and these faults, the local geology, and the underlying tectonic basement seem to be connected with that immediately adjacent to Puget Sound. 64, on-line) that the edge of the Crescent Formation offsets west along the Seattle Fault, with the Seattle Basin resulting from a gap between the main part of Siletiza and a northern block that has broken away. One study compared the relative elevation of two marshes on opposite sides of Whidbey Island, and determined that approximately 3,000 years ago an earthquake of M 6.57.0 caused 1 to 2 meters of uplift. This boundary would be the contact where northward movement of the basement rock of the Puget Lowland against the Olympic Peninsula is accommodated; it would be expected to be a significant seismological zone. [207] North of the RMFZ it follows a topographical lineament that can be traced to Rockport (on Hwy. Methane Plume Emissions Associated With Puget Sound Faults in the Sail Date . 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. Both the SPF and UPF are said to be oblique-slip transpressional; that is, the faults show both horizontal and vertical slip as the crustal blocks are pressed together. This seems geologically reasonable, as both the SWIF and RMFZ appear to be the contact between Tertiary Crescent Formation basement of Puget Sound on the west and the older Mesozoic (pre-Tertiary) mlange belt basement rocks under the Cascades on the east.[110]. [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. Full-Time. There's a one-in-10 chance that the next . Turkey's Fault Line is Similar to Faults Under Puget Sound | KUOW Officials on Tuesday said they believe that more than 7,000 people are dead after a magnitude 7.8 earthquake shook southern Turkey, near the Turkish-Syrian border. 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: [44] Another problem with the SWIF/RMFZ as CRBF is that a large westward step is required to connect from the RMFZ to the Saint Helens Zone (SHZ; see map), whereas the RMFZ turns easterly to align with the OWL. [197] This anticline, or uplifted fold, and the narrower width of the northern part of the SWCC, reflects an episode of compression of this formation. Please follow the steps below: . Aeromagnetic surveys,[13] seismic tomography,[14] and other studies have also contributed to locating and understanding these faults. The Seattle fault zone is where the forward edge of the slab, coming to the top of the ramp, breaks and slips into the Seattle Basin. [219] Various other faults in the North Cascades are older (being offset by the Straight Creek Fault) and are unrelated to the faults in Puget Sound. This is the Puget Lowland. Kinematic analysis suggests that if shortening (compression) in the Puget Lowland is directed to the northeast (i.e., parallel to Hood Canal and the Saddle Mountain deformation zone) and thus oblique to the Dewatto lineament, it should be subject to both strike-slip and dip-slip forces, implying a fault. According to the preeminent model, the "Puget Lowland thrust sheet hypothesis",[26] these faults, etc., occur within a sheet of crust about 14 to 20km deep that has separated from and is being thrust over deeper crustal blocks. King County Emergency Management. The answer is still unresolved. If entirely analogous, then "roof duplex" might also apply, and the Olympia Fault would be a reverse fault similar to the Tacoma Fault.