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. On the other hand, the contrasting character of the east-striking and southeast-striking segments is unsettling, and the change of direction somewhat difficult to reconcile with the observed fault traces. 112 earthquakes in the past 365 days. This follows the front of the Rosedale monocline, a gently southwest-tilting formation that forms the bluffs on which Tacoma is built. This map shows the primary earthquake faults in the Puget Sound and other less prominent faults. South of the OWL a definite eastern boundary has not been found, with some indications it is indefinite. In the wedge model of Pratt et al. The Doty Fault/Chehalis Basin sequence follows the cross-section X-X' shown on the, The long-range mapping plan area and current status of planned mapping can be seen at, For the County's interpretation of the geological hazard and anticipated impacts of a major earthquake, see the, Interstate 5 runs nearly due north from Everett to Mount Vernon, except for a stretch southeast of Conway that parallels one of these low-amplitude folds. See Snavely et al. [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. However, most seismic activity is not associated with any known fault. 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. Glacially deposited and shaped fill covers most of the lower elevations of Puget Sound. 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. Rainier is offset because the faults are deep and the conduits do not rise quite vertically.) 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.
Piecing together the puzzle of the Seattle Fault Zone This is the Puget Lowland. 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. [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.
New tsunami simulation predicts flooding on Olympic Peninsula | Tacoma "[50], The contrast of seismic velocities seen to the northwest is lacking in this section, suggesting that it is not the Coast RangeCascade contact.
Earthquake - King County [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. "We. The geology also suggests that the DMF is moving obliquely up a ramp that rises to the east,[35] possibly an ancient coastal shore. This may explain why the Seattle and Tacoma faults seem to have ruptured at nearly the same time.[127]. Puget Sound and San Juan islands. Initially it was not specified, and rather vaguely indicated to be west of Restoration Point (i.e., west of Puget Sound). (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. While these models vary in some details, both indicate that the Seattle Fault itself is capable of a magnitude 7.5 earthquake. Harold Tobin, . 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. 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. (See, There is a preliminary report of aeromagnetic and gravity mapping placing the eastern edge of the Siletz terrane under Lake Washington. It stands out in regard of its eastwest orientation, depth to bedrock, and hazard to an urban population center. Both of these are dip-slip (vertical) faults; the block between them has been popped up by compressive forces.
KUOW Public Radio on Twitter: "A UW researcher says the fault line that [190] These faults also cross the Saint Helens Zone (SHZ), a deep, north-northwest trending zone of seismicity that appears to be the contact between different crustal blocks. In 1870, as construction of the Northern Pacific began, Seattle numbered fewer than 1,200 souls. The first item on your list though is the fault of builders and nobody else. Where it intersects the northwest-trending Johnsons Swamp fault zone, easternmost member of the RMFZ.
ISNS 2359 Earthquakes and Volcanoes Chapter 5 Questions - Quizlet [221] Where it might run south of Seattle is not known; an argument has been made that it runs beneath Seattle[222] but this is still conjectural. [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.
PSE | Technical Resources for Construction - Puget Sound Energy There are other tsunami scenarios that are not accounted for in these maps, such as tsunamis caused by . [178] Alternately, the OS appears to coincide with a gravitational boundary in the upper crust that has been mapped striking southeast to The Dalles on the Columbia River,[179] where there is a swarm of similarly striking faults. "Most often, when we think of tsunamis, we think of our outer coast and communities along the Pacific Ocean. Seismic tomography studies show a change in seismic velocities across the northern end of the SWIF, suggesting that this is also part of the Coast RangeCascade contact. Movement on the southern segment of the DDMFZ that converges with the SCF the Darrington Fault was, as on the SCF itself, right-lateral. This fault seems to be associated with the Kingston arch anticline, and part of the uplift and basin pattern, but shortened because of the geometry of the SWIF. 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. Read More. 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. This is supported by geologically recent scarps and other signs of active faulting on the Saddle Mountain faults, and also discovery of a geophysical lineament running through Pleasant Harbor (south of Brinnon) that appears to truncate strands of the Seattle Fault.
Fault line puts Seattle at risk of 'The Big One' - UW Magazine There are numerous other faults (or fault zones) in the Puget Lowland, and around its edges, sketchily studied and largely unnamed. [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.
A Tsunami Hits Puget Sound: New Simulation Shows How It Unfolds 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. Olympic Peninsula, Washington has had: (M1.5 or greater) 0 earthquakes in the past 24 hours. 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). Sail Date . Several possible explanations of the enhanced conductivity have been considered; Eocene marine sediments containing brine are most likely (. 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. 1 earthquake in the past 7 days. [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. [29] This prospect is especially intriguing as a possible explanation of a cluster of seismic events around 1100 years ago.[30]. Analyze Instructions: Close. [99] This last problem is partly solved because there is a locus of seismicity, and presumably faulting, extending from the northern end of the SHZ to the northern end of the Western Rainier Zone (see Fig. Saint Helens and Mt. The Pacific Northwest Seismic Network (PNSN) reported at least three earthquakes within the past few days. These lineaments have been associated with possible zones of faulting in the crust and subducting plate.[212]. East of Puget Sound the basement of the Cascades province is various pre-Tertiary (older than 65 Ma) metamorphic rock. external structure, lines, and riggings; stand deck watches, such as helmsman and lookout underway; stand pier sentry, fire security, anchor, and . https://en.wikipedia.org/w/index.php?title=Puget_Sound_faults&oldid=1132982136, Creative Commons Attribution-ShareAlike License 3.0, A great subduction earthquake, such as the. 2-5 Cruises Age 60s. And like the SCF, strike-slip motion died out between 44 and 41 MA (due to plutonic intrusions). 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? A UW researcher says the fault line that caused earthquake that shook southern Turkey near the Turkish-Syrian border this week and killed more than 7,000 people is similar to the faults under Puget Sound. Very little is known about the structure of the deep crust (below about 30km or 19 miles), though this and other seismic tomography studies (such as Ramachandran 2001) provide tantalizing glimpses.
Harold Tobin, a researcher at the University of Washington and director of the Pacific Northwest Seismic Network, says the fault line that caused earthquake that shook southern Turkey near the Turkish-Syrian border and killed more than 7,000 people is similar to the faults under Puget Sound. Black squares are urban sewer outfalls, which don't match the bubble plumes' locations. [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. Pratt et al. fault Which of the following statements best describes elastic-rebound theory? [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]. A Seattle Fault quake could be as large as M7.5,160 but less than M7.0 is more probable. [60] Such seismic hazards were a major issue in the siting of the plant, as it is tucked between two active strands, and the influent and effluent pipelines cross multiple zones of disturbed ground. The Puget Sound Region is crisscrossed by fault lines and zones and also located close to the Cascadia Subduction Zone, where the Juan de Fuca and North American tectonic plates meet.
Turkey's fault line is similar to faults under Puget Sound Seattle Fault - Wikipedia [16] For the past 50 million years or so (since the early Eocene epoch) these have been thrust by subduction up against the North Cascades ("fixed block" in the diagram), which sit on the North American Plate.
Shallow fault below Seattle went undiscovered for a millennium 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. [181] What is unknown is whether this was due to a great subduction earthquake, to the noted earthquake on the Seattle Fault about that time, or to an earthquake on a local fault (e.g., the Olympia structure); there is some evidence that there were two earthquakes over a short time period.