[91] The relationship between these two fault zones is not entirely clear. fault Which of the following statements best describes elastic-rebound theory? [131], The Tacoma Fault was first identified by Gower, Yount & Crosson (1985) as a gravitational anomaly ("structure K") running east across the northern tip of Case and Carr Inlets, then southeast under Commencement Bay and towards the town of Puyallup. Whether the faulting continues eastward is not yet determined. According to the Washington state Department of Natural Resources, more than 1,000 earthquakes happen in Washington state each year! 0 magnitude subduction earthquake off the Washington coast would generate a tsunami capable of submerging not only coastal areas but also most of the Puget Sound shoreline . In the map above these are represented by the pair of dotted lines at the lower right. The structure of the Seattle Fault zone still have great uncertainty and there exist a number of interpretations. 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. Arcos' work suggests. It's due for another one,. 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. Harold Tobin, . News Media at VA Puget Sound health care, 206-764-2435, 206-764-2317. 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. The Seattle Fault crosses east-west through Puget Sound and downtown Seattle. Active faults and earthquakes in Washington state Seismic Scenario Catalog NEHRP site class and liquefaction susceptibility Seismic design categories Hazardous Minerals Lahar Hazards Landslides and landforms Inactive and abandoned mines Contact Us Susan Schnur Editor-in-Chief 360-701-6122 DNR is led by Commissioner of Public Lands Hilary Franz 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. [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. [29] This prospect is especially intriguing as a possible explanation of a cluster of seismic events around 1100 years ago.[30]. 3511 NE Second St. Renton, WA 98056. These faults also form the north and south boundaries of uplifted pre-Tertiary rock, suggesting that the faults come together at a lower level, much like one model of the Seattle and Tacoma faults, but at a smaller scale. 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). Washington State Earthquake Hazard Map Seattle Fault Lines 552 - Hood Canal fault zone (Class B) 570 - Seattle fault zone 572 - Southern Whidbey Island fault zone 575 - Saddle Mountain faults 581 - Tacoma fault zone USA Earthquake Hazard Map Source: United States Geological Survey Ready to retrofit? [71], These faults cut through the Western Mlange Belt (WMB; blue area in map), exposed from North Bend (on Interstate 90) to Mount Vernon. The Pacific Northwest Seismic Network (PNSN) reported at least three earthquakes within the past few days. 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). TTY Relay 711. "Most often, when we think of tsunamis, we think of our outer coast and communities along the Pacific Ocean. [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. Energize Eastside project is building a new substation and upgrading approximately 16 miles of existing transmission lines from Redmond to Renton. [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. 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. [19] These terranes were covered by the basalts of the Crescent Formation (part of Siletzia). [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. However, the Hood Canal fault has been "largely inferred"[147] due to a paucity of evidence, including lack of definite scarps and any other signs of active seismicity. It is of interest here because the various strands of the Seattle Fault change orientation where they appear to cross the OWL,[20] and various other features, such as the Rosedale monocline and Olympia structure, and a great many local topographical features, have parallel alignments. [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) Click "Plot" Draw. 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. The EPZ is active, being the locale of the 1995 M 5 Point Robinson earthquake.[136]. There's a one-in-10 chance that the next . 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). 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. [127], The Tacoma Fault (at right, and also between lines C and D on the Uplift and basin map, above) just north of the city of Tacoma, Washington has been described as "one of the most striking geophysical anomalies in the Puget Lowland". Initially it was not specified, and rather vaguely indicated to be west of Restoration Point (i.e., west of Puget Sound). 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. 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. 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. 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. The Woods Lake Fault, running past Lake Chaplain, corresponds closest to the mapped position of the southern end of Cheney's Mount Vernon Fault. A Coast Range Boundary Fault (CRBF, discussed above) was inferred on the basis of differences in the basement rock to the west and east of Puget Sound (the Crescent FormationCascadia core contact), and arbitrarily mapped at various locations including Lake Washington; north of the OWL this is now generally identified, with the Southern Whidbey Island Fault. This follows the front of the Rosedale monocline, a gently southwest-tilting formation that forms the bluffs on which Tacoma is built. Aeromagnetic surveys,[13] seismic tomography,[14] and other studies have also contributed to locating and understanding these faults. As all of these are thrust and reverse faults, they probably result from northeast directed regional compression. The fault type is subducting. [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. Analysis of seismic profiles extending 50 km across the Puget Lowland from Lake Washington to Hood Canal indicates . . 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. In 1870, as construction of the Northern Pacific began, Seattle numbered fewer than 1,200 souls. Job Description. 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. Puget Sound Energy. 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. 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. Geochemistry, Geophysics, Geosystems , 2021; 23 (1) DOI: 10.1029/2021GC010211 Cite This Page : [Paper No. [58], Paleoseismological studies of the SWIF are scant. [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). [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. 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. See Snavely et al. However, the SWCC is relatively shallow (no more than 15 km deep), and likely is draped over pre-Tertiary bedrock. If entirely analogous, then "roof duplex" might also apply, and the Olympia Fault would be a reverse fault similar to the Tacoma Fault. 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. One problem with this is that the parts of the SWIF east of Puget Sound do not show the velocity contrasts that would indicate contrasting rock types. [116] Subsequent authors were confident enough to trace the fault west of Bremerton to just north of Green Mountain (the northwestern corner of the Blue Hills uplift see "E" on the map a topographically prominent exposure of uplifted basalt) and just short of Hood Canal;[117] but reluctant to map the fault further west as the distinctive aeromagnetic lineament used to locate the Seattle Fault dies out just west of Bremerton. The map is from a 2007 report (click here to download) on seismic design categories in Washington. The first item on your list though is the fault of builders and nobody else. Study of surface deformation suggests possible unmapped faults near Federal Way, running between Sumner and Steilacoom, and south of Renton.[223]. [73] The presence of detritus from the Idaho Batholith[72] indicates a former location closer to southern Idaho. [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 length of the Doty Fault is problematical: the report in 2000 gave it as 65km (40 miles), but without comment or citation. [100], However, gravity and other data suggest that near the southern tip of Whidbey Island the Crescent Formation contact may turn away from the SWIF, and may even be reentrant under north Seattle,[101] forming the northwestern side of the Seattle Basin, and possibly connecting with the recently reported "Bremerton trend" of faulting running from the southern end of Hood Canal, through Sinclair Inlet (Bremerton), and across Puget Sound. [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. Extensive research has since shown the Seattle Fault to be part of a regional system of faults . [90], The RMFZ continues NNW past Fall City and Carnation, where strands of the RMFZ have been mapped making a gentle turn of 15 to 20 west to meet the Southern Whidbey Island Fault zone (SWIF, discussed above); the RMFZ is therefore considered to be an extension of the SWIF. [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]. It is believed that all of these faults, folds, basins, and uplifts are related. OLYMPIA, Wash. - A 9. This formation, up to 15km thick, is largely buried (from one to ten kilometers deep), and known mainly by magnetotellurics and other geophysical methods. South of the OWL a definite eastern boundary has not been found, with some indications it is indefinite. Although these faults are west of the Hood Canal Fault (previously presumed to be the western boundary of the Puget Lowland), new studies are revealing that the Saddle Mountain and related faults connect with the Seattle fault zone. Its capable magnitude is a megathrust quake exceeding 9.0. It appears the entire DDMFZ and Leech River fault system was pushed onto the early continental margin from an original alignment along the OWL. NW-striking black lines are right-lateral bedrock faults thought to be subsidiary to Dar- rington-Devils Mountain fault zone (Dragovich and DeOme, 2006). [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). 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. 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. 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. Plot Type: X-Section Depth Cumulative # Mag-Time. Cheney also mapped the Lake Chaplain Fault, parallel and just east of the MVF, from Lake Chaplain to Granite Falls. "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 . Get directions. Review for American Constellation to U.S.A. chatuga. to the north, past Lummi Island is contrary to the prevailing consensus that the DMF is not offset. [142]) This reflects westward thrusting of the Seattle Uplift into the Dewatto basin, a northwestern extension of the Tacoma basin. 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). But. 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. [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). [102] Or the Crescent margin may simply (and quietly) just run south-southeast under Seattle to the WRZ. [153] For these reasons this is now a questioned fault, and is indicated on the map as a dashed line. [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. And like the SCF, strike-slip motion died out between 44 and 41 MA (due to plutonic intrusions). 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]. 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]. [109] It extends as far east as (and probably terminates at) the Rattlesnake Mountain Fault Zone (RMFZ; the southern extension of the SWIF) near Fall City. Nor does this uplift delineate any significant basin between it and the Devils Mountain Fault. [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. 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. [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. Sail Date: October 2022 . The 1949, 1965, and 2001 Puget Sound earthquakes were the result of _____ fault movement within the Juan de Fuca plate. Combined with continued aggressive electric conservation efforts, Energize . 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? [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.