(A) Map of the Seattle fault zone (SFZ) in the central Puget Sound With inland, Puget Sound faults, like the Seattle Fault, the risk is comparatively smaller. 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. [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). 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. 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). This is only one of a series of active large crustal faults in the Puget Lowland. The northern end of the Crescent Formation (aka Metchosin Formation) has been identified as the eastwest trending Leech River Fault on the southern tip of Vancouver Island. [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. Next to a 4-6 lines highways with 90db noise and cancerous pollution. This map of Puget Sound shows the location of the methane plumes (yellow and white circles) detected along the ship's path (purple). "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 . Modeling a Magnitude 7.2 Earthquake on the Seattle Fault Zone in to the north, past Lummi Island is contrary to the prevailing consensus that the DMF is not offset. See Snavely et al. Tacoma's Gain is Seattle's Pain. 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. These include the: Southern Whidbey Island Fault (SWIF) Seattle Fault Devils Mountain Fault Strawberry Point fault Utsalady Point fault Calawah fault Barnes Creek 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. [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. Puget Sound Tsunami Simulation - National Oceanic and Atmospheric Extensive research has since shown the Seattle Fault to be part of a regional system of faults . Plot Type: X-Section Depth Cumulative # Mag-Time. 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. Sail Date: October 2022 . 14 earthquakes in the past 30 days. ISNS 2359 Earthquakes and Volcanoes Chapter 5 Questions - Quizlet NW-striking black lines are right-lateral bedrock faults thought to be subsidiary to Dar- rington-Devils Mountain fault zone (Dragovich and DeOme, 2006). [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". OLYMPIA, Wash. - A 9. [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. 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. 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. [193] The SHZ and WRZ lie just outside the topographical basin that constitutes the Puget Lowland (see image), do not participate in the uplift and basin pattern, and unlike the rest of the faults in the Puget Lowland (which are reverse or thrust faults reflecting mostly compressive forces) they appear to be strike-slip faults; they reflect a geological context distinctly different from the rest of the Puget Lowland. However, there are indications that the fault is segmented, which might limit rupturing and earthquake magnitude.[36]. [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). (Enter only one word per blank.) 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. 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]. 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. Could a Tsunami Hit Puget Sound? - Washington Sea Grant Five Puget Sound cities likely to feel strong shaking in a megaquake Because the Seattle and Tacoma faults run directly under the biggest concentration of population and development in the region, more damage would be expected, but all the faults reviewed here may be capable of causing severe damage locally, and disrupting the regional transportation infrastructure, including highways, railways, and pipelines. 3511 NE Second St. Renton, WA 98056. [Paper No. Earthquake Fault Maps in Seattle and Washington State 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. 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). [129] The western part is an active eastwest striking north dipping reverse fault that separates the Seattle Uplift and the Tacoma Basin, with approximately 30 miles (50km) of identified surface rupture. 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. 48), along the edge of a formation known as the Southern Washington Cascades Conductor. A single earthquake in Seattle could cause a catastrophic situation for the northwest corner of the state, a new report from Washington's Department of Natural Resources found. Ongoing mapping is revealing more faults. [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. [58], Paleoseismological studies of the SWIF are scant. [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. [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. (See, There is a preliminary report of aeromagnetic and gravity mapping placing the eastern edge of the Siletz terrane under Lake Washington. 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. On this Wikipedia the language links are at the top of the page across from the article title. Yet the SHZ and WRZ may be integral to the regional geology of Puget Sound, possibly revealing some deep and significant facets, and may also present significant seismic hazard. "Most often, when we think of tsunamis, we think of our outer coast and communities along the Pacific Ocean. [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. [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. This is the Puget Lowland. [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 map shows areas of seismic risk from high (red) to low (grayish-green). 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. Another model (of Stanley, Villaseor & Benz 1999, USGS Open-File Report 990311) not so much in competition with the first as complementing it used seismic and other data to create a 3-D tectonic model of the whole crust; this was then analyzed using finite element methods to determine regional geodynamic characteristics. Other similar lineaments (such as from Astoria to Glacier Peak) align with various topographical features and changes in fault orientation. Though a 2012 study[149] interpreted a different variety of tomographic data as showing the Hood Canal fault, other mapping has "found no convincing evidence for the existence of this fault",[150] considers it doubtful,[151] depicted it "with low level of confidence",[152] or omits it entirely. There is a general pattern where most of these faults partition a series of basins and uplifts, each about 20km wide. Job Description. The Bellingham BayChaplain fault zone was first mapped by Cheney in 1976 as running from near Chaplain Lake (north of Sultan) NNW past Bellingham Bay. It is not known to be seismic indeed, there is very little seismicity south of the Tacoma Basin as far as Chehalis[169] and not even conclusively established to be a fault. A Seattle Fault quake could be as large as M7.5,160 but less than M7.0 is more probable. It is coincident with, and possibly a result of uplift on, the Rattlesnake Mountain Fault Zone (RMFZ), a band of at least eleven faults that show both dip-slip (vertical) and right-lateral strike-slip motion. Saint Helens and Mt. 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. The lowest exposed strata of Tiger Mountain, the mid-Eocene marine sediments of the Raging River formation, may be correlative with the SWCC. The fault type is subducting. Puget Sound faults - Wikipedia Some upper-crustal formations (such as the Western and Eastern Melange Belts, see, There is a general north or northeast directed compression within the Lowland causing folds, which eventually break to become, This page was last edited on 11 January 2023, at 17:28. ", 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. [98] This turns and runs just south of Victoria, nearly in-line with the SWIF. Energy builds up as elastic strain in rocks. Sail Date . 1958 and Geologic Map GM-34 for details.). ), 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". 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]. If the entire 125km length ruptured in a single event the resulting earthquake could be as large as magnitude 7.5. 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). 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. [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. But. The Seattle Fault crosses east-west through Puget Sound and downtown Seattle. E.g., mapping along the Rattlesnake Mountain Fault Zone has revealed a complex network of active or potentially active faults across (and likely beyond) the lower Snoqualmie Valley, including the Cherry Creek Fault Zone, scene of the 1996 M 5.3 Duvall earthquake. If entirely analogous, then "roof duplex" might also apply, and the Olympia Fault would be a reverse fault similar to the Tacoma Fault. [57] Mapping of areas further east that might clarify the pattern is not currently planned. ), 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. The structure of the Seattle Fault zone still have great uncertainty and there exist a number of interpretations. They estimate the fault is within a few miles of the surface and was active as recently as 1,000 to 1,100 years ago. 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. 39 earthquakes in the past 365 days. 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). [103] Other seismic tomography has tantalizingly suggested three north-striking strands under Seattle, and a fourth just east of Lake Washington. Analysis of seismic profiles extending 50 km across the Puget Lowland from Lake Washington to Hood Canal indicates . 182-3]", "Western limits of the Seattle fault zone and its interaction with the Olympic Peninsula, Washington", "Seismic reflection imaging across the eastern portions of the Tacoma fault zone", "The western extension of the Seattle fault: new insights from seismic reflection data", "Seismic Characterization of the Seattle and Southern Whidbey Island Fault Zones in the Snoqualmie River Valley, Washington", "Fault number 552, Hood Canal fault zone", "Radiocarbon Ages of Probable Coseismic Features from the Olympic Peninsula and Lake Sammamish, Washington", "Geologic map of the Summit Lake 7.5-minute quadrangle, Thurston and Mason Counties, Washington", "The Olympia structure; ramp or discontinuity? 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 bends are located where they intercept a "subtle geological structure"[202] of "possible fundamental importance",[203] a NNE striking zone (line "A" on the map) of various faults (including the Tokul Creek Fault NNE of Snoqualmie) and early-Miocene (about 24 Ma) volcanic vents and intrusive bodies (plutons and batholiths) extending from Portland to Glacier Peak;[204] it also marks the change in regional fault orientation noted above. [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. 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. Geologic map of southwestern Washington (GM-34).

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