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While the great subduction events release much energy (around magnitude 9), that energy is spread over a large area, and largely centered near the coast. 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. [89] The northern end of the mountain falls off where it crosses the eastern end of the Seattle Fault, which in turn terminates at the RMFZ; Rattlesnake Mountain forms the eastern edge of the Seattle Uplift. The Devils Mountain Fault (DMF) runs about 125km (75 miles) from the town of Darrington in the Cascade foothills due west to the northern tip of Whidbey Island, and on towards Victoria, British Columbia, where the DMF is believed to join the Leech River fault system at the southern end of Vancouver Island. In the angle between these is located the minor Lincoln Creek uplift, the Doty Hills, and, further west, an impressive chunk of Crescent basalt. Combined with continued aggressive electric conservation efforts, Energize . [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. 39 earthquakes in the past 365 days. 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. [215] [158] Vertical movement on these faults has created prominent scarps that have dammed Price Lake and (just north of Saddle Mountain) Lilliwaup Swamp. [73] The presence of detritus from the Idaho Batholith[72] indicates a former location closer to southern Idaho. As all of these are thrust and reverse faults, they probably result from northeast directed regional compression. 1958 and Geologic Map GM-34 for details.). [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. [44] The significance of this whether the edge of the Crescent Formation (and implicitly of the Siletz terrane) turns southward (discussed below), or the metamorphic basement is supplanted here by other volcanic rock is not known. American Seattle Cruise Reviews - Cruise Critic Energy builds up as elastic strain in rocks. 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: [8] As of 1985 only the Saddle Mountain Faults had been shown to have Holocene activity (since the last ice age, about 12,000 years ago). ), and headed for the definitely active Saint Helens Zone; this appears to be a large-scale structure. Geologic map of southwestern Washington (GM-34). UW researchers model tsunami hazards on the Northwest coast 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 Pacific Northwest Seismic Network (PNSN) reported at least three earthquakes within the past few days. ISNS Ch 5 Flashcards | Quizlet $30 to $33 Hourly. Initially it was not specified, and rather vaguely indicated to be west of Restoration Point (i.e., west of Puget Sound). Nurse Information Line at VA Puget Sound health care, 800-329-8387 x4. However, the SWCC is relatively shallow (no more than 15 km deep), and likely is draped over pre-Tertiary bedrock. Interpretation of the eastern part of the Tacoma Fault is not entirely settled. The question of where on Puget Sound the line would ultimately end was intentionally left open, and the region's fledgling cities began competing furiously for the good fortune of a major railroad terminus. East of Puget Sound the basement of the Cascades province is various pre-Tertiary (older than 65 Ma) metamorphic rock. And the magnitude used to generate that wave is only about 7.5, as opposed to a magnitude-9 earthquake off the coast. However, there are indications that the fault is segmented, which might limit rupturing and earthquake magnitude.[36]. 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). "[31] More particularly, the concentration of seismicity under Puget Sound south of the Seattle Fault is attributed to uplift of that block, bounded by the Seattle, Tacoma, and Dewatto faults on the north, south, and west (the eastern boundary is not determined), creating the Seattle Uplift. If, as this model suggests, the various faults are interconnected within the thrust sheet, there is a possibility that one earthquake could trigger others. A recent (2009) analysis of aeromagnetic data[159] suggests that it extends at least 35km, from the latitude of the Seattle Fault (the Hamma Hamma River) to about 6km south of Lake Cushman. The Seattle Fault crosses east-west through Puget Sound and downtown Seattle. They run . [83], The CCFZ appears to be related to the parallel Tokul Creek fault zone to the south; both appear to be conjugate faults[84] to the northwest-trending SWIF. [52], Subsequent mapping shows the SWIF wrapping around the eastern end of the Seattle Basin to merge with the Rattlesnake Mountain Fault Zone (RMFZ); the RMFZ, despite the approximately 15 bend and different context, is now believed to be the southern extension of the SWIF. Yet the former is only the first of at least six more parallel southeast striking faults, which do cross the Salzer Creek Fault. Observing these topographical features, some parallel gravity gradients, and a "very active zone of minor seismicity", William Rogers inferred in 1970 a "fault or other major structural feature".[64]. 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. 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. Geochemistry, Geophysics, Geosystems , 2021; 23 (1) DOI: 10.1029/2021GC010211 Cite This Page : A 2001 study[148] using high-resolution seismic tomography questioned its existence. [162] Trench studies indicate major earthquakes (in the range of M 6. to 7.8) on the Saddle Mountain faults [163] at nearly the same time (give or take a century) as the great quake on the Seattle Fault about 1100 years ago (900930 AD). Posted: 12 days ago. [156], The Saddle Mountain Faults ("East" and "West", and not to be confused with a different Saddle Mountains Fault in Adams county, eastern Washington[157]), are a set of northeast trending reverse faults on the south-east flank of the Olympic Mountains near Lake Cushman first described in 1973 and 1975. Five Puget Sound cities likely to feel strong shaking in a megaquake 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. It stands out in regard of its eastwest orientation, depth to bedrock, and hazard to an urban population center. Movement on the southern segment of the DDMFZ that converges with the SCF the Darrington Fault was, as on the SCF itself, right-lateral. [200], Mount St. Helens and Mount Rainier are located where their associated fault zones make a bend (see map, above).[201](Mt. [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. Here the main strand on the western edge merges with the Sultan River Fault under the Sultan River. A new view is developing that the regional tectonic boundary is not under Hood Canal, but just to the west, involving the Saddle Mountain fault zone (discussed below) and associated faults. ", Because of the geometry of the SWIF and the Kingston arch, the "uplift of unknown origin" between them is smaller, and the fault separating the uplift from the arch (the Lofall Fault, discovered relatively recently by, Strictly speaking the southern edge of the Black Hills Uplift would be the southeast striking Scammon Creek Fault that converges with the east striking Doty Fault at Chehalis. 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. There's a one-in-10 chance that the next . The Olympia structure also known as the Legislature fault[168] is an 80km long gravitational and aeromagnetic anomaly that separates the sedimentary deposits of the Tacoma Basin from the basalt of the Black Hills Uplift (between lines A and B on the map). These lineaments have been associated with possible zones of faulting in the crust and subducting plate.[212]. [187] Such a length would be comparable to the length of the Seattle or Tacoma faults, and capable of an earthquake of M 6.7. These mlanges may have been off-shore islands or seamounts that were caught between the Olympic terrane and the North American continent, and were pushed up (obducted) onto the latter. 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. Devils Mountain Fault Zone, Northern Puget Sound, Washington This section of the SWIF forms the southwestern side of the Everett Basin[48] (see map), which is notably aseismic in that essentially no shallow (less than 12km deep) earthquakes have occurred there, or on the section of the SWIF adjoining it, in the first 38 years of instrumental recording. However, an enormous threat lurks just off the coast of the Pacific Northwest. If entirely analogous, then "roof duplex" might also apply, and the Olympia Fault would be a reverse fault similar to the Tacoma Fault. And since those models for the Seattle Fault were published, there've actually been many more Puget Sound faults discovered. [142]) This reflects westward thrusting of the Seattle Uplift into the Dewatto basin, a northwestern extension of the Tacoma basin. For information about the Energize Eastside project, . Pratt et al. Puget Sound quake likely in Seattle Fault zone, geologists say - Phys.org [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. "We. [153] For these reasons this is now a questioned fault, and is indicated on the map as a dashed line. These include (from north to south, see map) the: Devils Mountain Fault Strawberry Point and Utsalady Point faults Southern Whidbey Island Fault (SWIF) There are some interesting relationships here. And though the faults in this area are not notably seismogenic, the southeast striking faults seem to be en echelon with the Olympia structure (fault? The SWCC appears to be Tertiary marine sediments, not the pre-Tertiary metamorphic rock of the Cascades province; this would seem to make it part of the Coast Range province, with the Coast RangeCascade contact further east. [71], These faults cut through the Western Mlange Belt (WMB; blue area in map), exposed from North Bend (on Interstate 90) to Mount Vernon. [51] Black lines show the South Whidbey Island Fault Zone, the . 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. [5] The southern limit nearly matches the southern limit of the glaciation; possibly the seismicity reflects rebound of the upper crust after being stressed by the weight of the glacial ice. [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. 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. [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). But. But their significance to the Puget Sound area is unknown. (Not included in QFFDB. Marine technician Sony Brugger, right, retrieves underwater sampling equipment during a December 2020 research cruise aboard the RV Rachel Carson. [160] The Canyon River Fault is a major fault in itself, associated with a 40km long lineament and distinct late Holocene scarps of up to 3 meters.[161]. Active tectonics of the Seattle fault and central Puget sound TTY Relay 711. They are also on-strike with a swarm of faults on the Columbia River, bracketing The Dalles. This structure is shown in the gravitational mapping of 1965, but without comment. 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. Bubbles of methane rising from seafloor in Puget Sound The study was. More than a millennium ago, a quake estimated at a magnitude 7 on the Seattle Fault thrust land upward as much as 23 feet and submerged 200-acre chunks of forest in central Puget Sound and Lake .