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";s:4:"text";s:23591:"Black lines show the South Whidbey Island Fault Zone, the Seattle Fault Zone and the Tacoma. [70] Although the intervening section has not been mapped, geologists believe the GFFZ connects with the McMurray FZ to the north, and forms the eastern boundary of the Everett Basin. . [206] This line may also mark the northwestern boundary of the SWCC. ), 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. This pocket is catching a stream of terranes (crustal blocks about 20 to 30km thick[18]) which the Pacific plate is pushing up the western edge of North America, and in the process imparting a bit of clockwise rotation to southwestern Washington and most of Oregon; the result has been characterized as a train wreck. [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. [164] Such quakes pose a serious threat to the City of Tacoma's dams at Lake Cushman,[165] located in the fault zone,[166] and to everyone downstream on the Skokomish River. The discovery was an alarm bell for engineers and emergency planners. Just past them is the parallel Olympia Structure, which as a geophysical lineament has been traced to a point due east of Chehalis;[189] these would seem to be related somehow, but the nature of that relationship is not yet known. Black lines show the South Whidbey Island Fault Zone, the . "Most often, when we think of tsunamis, we think of our outer coast and communities along the Pacific Ocean. 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. And like the SCF, strike-slip motion died out between 44 and 41 MA (due to plutonic intrusions). Review for American Constellation to U.S.A. chatuga. [92] This is where the SWIF encounters the edge of the Western and Eastern Melange Belts (remnants of a mid-Cretaceous subduction zone[93]); the RMFZ is where the Seattle Uplift is being forced against the Western Melange belt[94], To the north the Melange Belt is manifested as the Rogers Belt, a zone of low-amplitude folding stretching from Monroe to Mount Vernon; the apparent western edge of this zone is on-strike with the RMFZ. Conjugate faults are secondary faults that branch off from opposite sides of a strike-slip fault at approximately the same angle. [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. While these models vary in some details, both indicate that the Seattle Fault itself is capable of a magnitude 7.5 earthquake. All this is explained by right-lateral strike-slip motion on the Straight Creek Fault, which initiated about 50 to 48 Ma (millions of years ago). This ramp could be either in the lower crustal blocks, or where the thrust sheet has split and one part is being forced over the next. [210] The zone between these two lines, reflecting changes in regional structure, seismicity, fault orientation, and possibly the underlying lithospheric structure, appears to be a major structural boundary in the Puget Lowland. West of Puget Sound the tectonic basement of the Coast Range geologic province is the approximately 50 million year (Ma) old marine basalts of the Crescent Formation, part of the Siletzia terrane that underlies western Washington and Oregon. 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. [66] This is located on a topographical lineament that aligns with Mount Vernon to the north, and, to the south, the city of Granite Falls and Lake Chaplain (just north of Sultan). [87], Rattlesnake Mountain is a prominent NNW trending ridge just west of North Bend (about 25 miles east of Seattle). [96] As the juxtaposition of various disparate tectonic structures in northwest Washington requires significant strike-slip movement, it is further expected that this contact will be a major fault.[97]. 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. [120] However, the Saddle Mountain fault zone is not quite reciprocally aligned,[121] trending more northerly to where it encounters westeast trending faults (including the Hamma Hamma fault zone) that appear to be a westward extension of the Seattle Fault zone. 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. The ultimate driver of the stresses that cause earthquakes are the motions of the tectonic plates: material from the Earth's mantle rises at spreading centers, and moves out as plates of oceanic crust which eventually are subducted under the more buoyant plates of continental crust. Other faults to the south and southeast the Frigid Creek Fault and (to the west) Canyon River Fault suggest an extended zone of faulting at least 45km long. "[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. In the previous study seismicity, surface geology, and geophysical data were modeled in order to examine the fault structuring of the upper crust. [209] Between the Cherry Creek and parallel Tokul Creek faults is a contact between formations of the Western Melange Belt. [102] Or the Crescent margin may simply (and quietly) just run south-southeast under Seattle to the WRZ. These include the: Southern Whidbey Island Fault (SWIF) Seattle Fault Devils Mountain Fault Strawberry Point fault Utsalady Point fault Calawah fault Barnes Creek [91] The relationship between these two fault zones is not entirely clear. The QFFDB, citing lack of consensus, ignores the eastern part. We use an extensive network of marine high-resolution and conventional industry seismic-reflection data to constrain the location, shallow structure, and displacement rates of the Seattle fault zone and crosscutting high-angle faults in the Puget Lowland of western Washington. 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. [198], Does the SHZ extend north? The San Juan Island and Leach River faults crossing the southern end of Vancouver Island are significant and undoubtedly connected with the DarringtonDevils Mountain and Southern Whidbey Island faults, and certainly of particular interest to the residents of Victoria, B.C. It is believed capable of generating earthquakes of at least magnitude 7, and there is evidence of such a quake approximately 1,000 years ago, possibly the same earthquake documented on the Seattle Fault 24 miles (38km) to the north. Fault lines in the New Madrid seismic zone are being mapped, thanks in part to . A similar line aligns with the termination of the WRZ, SHZ, and Gales Creek Fault Zone (northwest of Portland), with faulting along the upper Nehalem River on the Oregon coast,[211] and a topographical contrast at the coast (between Neahkahnie Mountain and the lower Nehalem River valley) distinct enough to be seen on the seismicity map above (due west of Portland). Several possible explanations of the enhanced conductivity have been considered; Eocene marine sediments containing brine are most likely (. As all of these are thrust and reverse faults, they probably result from northeast directed regional compression. But. This is being obliquely overridden by the North American plate coming out of the northeast, which has formed a bend in the subducting plate and in the forearc basin above it. [9] Not until 1992 was the first of the lowland faults, the Seattle Fault, confirmed to be an actual fault with Holocene activity, and the barest minimum of its history established.[10]. Harold Tobin, a researcher at the University of Washington and director of the Pacific Northwest Seismic Network, says the fault line that caused this disaster is similar to the faults under Puget Sound. Marine seismic reflection surveys on either side of Whidbey Island extend the known length of these faults to at least 26 and 28km (about 15 miles). This is the Puget Lowland. The fault type is subducting. [51] The history and capabilities of the Frigid Creek Fault are not known. The Puget Sound faults under the heavily populated Puget Sound region (Puget Lowland) of Washington state form a regional complex of interrelated seismogenic (earthquake-causing) geologic faults. 10+ Cruises Age 2020s. 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). [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. These maps are based on only one Cascadia scenario. 14 earthquakes in the past 30 days. [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. [142]) This reflects westward thrusting of the Seattle Uplift into the Dewatto basin, a northwestern extension of the Tacoma basin. Western Washington lies over the Cascadia subduction zone, where the Juan de Fuca Plate is subducting towards the east (see diagram, right). South of the OWL a definite eastern boundary has not been found, with some indications it is indefinite. Energy builds up as elastic strain in rocks. 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. Although the largely unstudied White River Fault (WRF) appears to lie just outside the Puget Lowland, it may actually connect under the Muckleshoot Basin to the East Passage Zone and the Tacoma Fault (map). ", 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. - Read More Expert Puts Turkey, Syria Quake into Perspective | FOX 13 This formation, up to 15km thick, is largely buried (from one to ten kilometers deep), and known mainly by magnetotellurics and other geophysical methods. 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). A parallel line ("B") about 15 miles (25 kilometers) to the west corresponds to the western limit of a zone of seismicity stretching from the WRZ to southwest of Portland. At the northern end the right-lateral McMurray Fault Zone (MFZ) straddles Lake McMurray, just south of the Devils Mountain Fault, and is suspected of being a major bounding fault. [82] 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]. fault Which of the following statements best describes elastic-rebound theory? 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. Doubts on the connectivity of these faults led to abandonment of this name in 1986[65] when Cheney mapped the Mount Vernon fault (MVF) from near Sultan northwest past Lummi Island (west side of Bellingham Bay, visible at the top of the map), crossing the Devils Mountain Fault (DMF, part of the DarringtonDevils Mountain Fault Zone) near Mount Vernon. PNSN staff will continue to develop this section of the web site but to find more good information now, visit these resources: [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. [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]. 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. [79] It is deemed a "major active or potentially active" structure. 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 Doty fault has been mapped from the north side of the Chehalis airport due west to the old logging town of Doty (due north of Pe Ell), paralleled most of that distance by its twin, the Salzer Creek Fault, about half a mile to the north. An earthquake occurs along a south-moving fault. This map shows areas of seismic risk from high (red) to low (grayish-green). These faults are not quite aligned with the Olympia structure, striking N75W (285) rather than N45W (315). 39 earthquakes in the past 365 days. [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. [11] Marine seismic reflection surveys on Puget Sound where it cuts across the various faults have provided cross-sectional views of the structure of some of these faults, and an intense, wide-area combined on-shore/off-shore study in 1998 (Seismic Hazards Investigation in Puget Sound, or SHIPS)[12] resulted in a three-dimensional model of much of the subsurface geometry. The 1949, 1965, and 2001 Puget Sound earthquakes were the result of _____ fault movement within the Juan de Fuca plate. Harold Tobin, . 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. Black lines show the South Whidbey Island Fault Zone, the Seattle Fault Zone and the Tacoma Fault Zone. The Frigid Creek fault seems more directly aligned with this southwestward extension of the Seattle Fault, but such a connection seems to be as yet unremarked by geologists. [143] Such interconnection also suggests a capability for larger earthquakes (> M7 for the Seattle Fault); the amount of increased risk is unknown.[144]. [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. But it does not appear that there have been studies of the deeper structure of these faults, or whether there has been any recent activity. [103] Other seismic tomography has tantalizingly suggested three north-striking strands under Seattle, and a fourth just east of Lake Washington. 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. [72] The WMB is an assemblage of Late Jurassic and Cretaceous rock (some of it as much as 166 million years old) collected in the accretionary wedge (or prism) of a subduction zone. . The principal effects of this complex interplay of forces on the near-surface crust underlying the Puget Lowland are: Further complicating this is a feature of unknown structure and origin, the OlympicWallowa Lineament (OWL). [80], In the crowded field of active or potentially active fault zones that have been discovered in the lower Snoqualmie Valley, the Cherry Creek fault zone is particularly notable because east of Duvall[81] it passes through a hotspot of active seismicity, including the 1996 '"`UNIQ--templatestyles-00000057-QINU`"'ML 5.3 Duvall earthquake. [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). 1 earthquake in the past 7 days. Methane Plume Emissions Associated With Puget Sound Faults in the Cascadia Forearc CC BY 4.0 Authors: H. Paul Johnson University of Washington Seattle S. G. Merle National Oceanic and. [38] These earthquakes probably caused tsunamis, and several nearby locations have evidence of tsunamis not correlated with other known quakes. [215] 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. The worst of the tsunami would hit the Pacific Coast and San Juan Islands area but the interior of Puget Sound between Edmonds, Tacoma, and Hoodsport could see waves 10 feet or higher, the. The most recent Seattle Fault earthquake was about 1,100 years ago; The Seattle Fault has been active about three or four times in the past 3,000 years. [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. 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. 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. [2] All this is at risk of earthquakes from three sources:[3]. 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. The Seattle Fault was first recognized as a significant seismic hazard in 1992, when a set of reports showed that about 1,100 years ago it was the scene of a major earthquake of about magnitude 7 - an event that entered Native American oral legend. There is no firm evidence that this has occurred in the Seattle fault zone near Puget Sound, although a low terrace of 1 m or less formed during a moderate earthquake would be difficult to. 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). [174] Although no surface traces of faulting have been found in either the Holocene glacial sediments or the basalts of the Black Hills,[175] on the basis of well-drilling logs a fault has been mapped striking southeast from Offut Lake (just west of Rainier); it appears to be in line with the easternmost fault mapped in the CentraliaChehalis area.[176]. The Straight Creek Fault is a major structure in the North Cascades, but has not been active for over 30 million years. 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). These features suggest that the southern Puget Lowland is influenced by the deep crust and even the subducting Juan de Fuca plate, but the details and implications are not yet known. Washington's fault lines tend to sweep east-west. This map of Puget Sound shows the location of the methane plumes (yellow and white circles) detected along the ship's path (purple). Black squares are urban sewer outfalls, which don't match the bubble plumes' locations. [95], (Rattlesnake Mountain Fault Zone not included in QFFDB. Nurse Recruiter at VA Puget Sound health care, 206-764-2487. A magnitude 7.1 earthquake in the Tacoma Fault Zone A plausible scenario for the southern Puget Sound region, Washington May 18, 2010 Citation Information. After all, Olympia, which is the closest of the cities to the megathrust fault, is estimated to experience the least severe shaking; at the same time, many cities on the east side of the Puget Sound further away from the fault experience much stronger shaking. One animation shows the expected path of a Puget Sound tsunami generated by a quake on the Seattle Fault. On the north is the HelenaHaystack mlange (HH mlange, purple in the diagram at right), on the south the Western and Eastern mlange belts (WEMB, blue). [170] Gower, Yount & Crosson (1985), labelling it "structure L", mapped it from Shelton (near the Olympic foothills) southeast to Olympia (pretty nearly right under the state Legislature), directly under the town of Rainier, to a point due east of the Doty Fault, and apparently marking the northeastern limit of a band of southeast striking faults in the Centralia-Chehalis area. [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. The mapped surface traces are only 5km long, but LIDAR-derived imagery shows longer lineaments, with the traces cutting Holocene alluvial traces. Saint Helens and Mt. 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: ";s:7:"keyword";s:26:"fault lines in puget sound";s:5:"links";s:661:"Jason Foster Obituary,
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