fault lines in puget sound

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. Does the public have a right to walk across a - Puget Sound Institute Piecing together the puzzle of the Seattle Fault Zone [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. Contact Us | VA Puget Sound Health Care | Veterans Affairs 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]. [182], The Doty Fault the southernmost of the uplift-and-basin dividing faults reviewed here, and located just north of the Chehalis Basin is one of nearly a dozen faults mapped in the CentraliaChehalis coal district in 1958. [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. [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. A different mountain and fault zone of the same name are located near Pasco; see QFFDB Fault #565), The southern end of Rattlesnake Mountain is truncated at the OlympicWallowa Lineament (OWL), and the faults turn easterly to merge with the OWL. 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. [155] North of the Seattle Fault accommodation of regional movement may be along the northwest-striking Dabob Bay Fault Zone. If entirely analogous, then "roof duplex" might also apply, and the Olympia Fault would be a reverse fault similar to the Tacoma 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. Somewhere between Puget Sound and Cascades foothills these two geological provinces come into contact. [6] The first definite indications of most of these faults came from gravitational mapping in 1965,[7] and their likely existence noted on mapping in 1980 and 1985. $30 to $33 Hourly. 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). Detailed mapping of this area since 2006 has revealed a complex pattern of faults. 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. [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. 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. King County Emergency Management. [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. 3511 NE Second St. Renton, WA 98056. And like the SCF, strike-slip motion died out between 44 and 41 MA (due to plutonic intrusions). 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. Other similar lineaments (such as from Astoria to Glacier Peak) align with various topographical features and changes in fault orientation. Geographic boundaries of Puget Sound and the Salish Sea These include (from north to south, see map) the: Devils Mountain Fault Strawberry Point and Utsalady Point faults Southern Whidbey Island Fault (SWIF) (See, There is a preliminary report of aeromagnetic and gravity mapping placing the eastern edge of the Siletz terrane under Lake Washington. 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). Today's Earthquakes in Olympic Peninsula, Washington [138] It arises from the contrast between the denser and more magnetic basalt of the Crescent Formation that has been uplifted to the east, and the glacial sediments that have filled the Dewatto basin to the west. It does bound the north side of the Chehalis basin, but the south boundary of the Black Hills Uplift is more properly the southeast striking Scammon Creek Fault that converges with the DotySalzer Creek Fault just north of Chehalis. Hood Canal marks an abrupt change of physiography between the Puget Lowland and the Olympic Mountains to the west. Study of surface deformation suggests possible unmapped faults near Federal Way, running between Sumner and Steilacoom, and south of Renton.[223]. Initially it was not specified, and rather vaguely indicated to be west of Restoration Point (i.e., west of Puget Sound). [113], Determination of the western terminus of the Seattle Fault has been problematic, and has implications for the entire west side of the Puget Lowland. Saint Helens and Mt. 39 earthquakes in the past 365 days. 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 . [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]. [82] This MSH-MR-GP lineament is believed to reflect a "long-lived deep-seated lithospheric flaw that has exerted major control on transfer of magma to the upper crust of southern Washington for approximately the last 25 [million years]";[203] it has been attributed to the geometry of the subducting Juan de Fuca plate.[205]. [106] There is an intriguing view from Stanley, Villaseor & Benz (1999) (see Fig. Pratt et al. The fault type is subducting. [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. [198], Does the SHZ extend north? The implications of this are not only "the possibility of a moderate to large crustal earthquake along the SHZ", but that the tectonics under Puget Sound are more complicated than yet understood, and may involve differences in the regional stress patterns not reflected in current earthquake hazard assessments. Just four miles (6km) south the city of Oak Harbor straddles several stands of the Utsalady Point Fault (UPF) as they head roughly east-southeast towards Utsalady Point at the north end of Camano Island. [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. Black lines show the South Whidbey Island Fault Zone, the . Analysis of seismic profiles extending 50 km across the Puget Lowland from Lake Washington to Hood Canal indicates . It appears that the Seattle Uplift is acting as a rigid block, with the Tacoma, Dewatto, and Seattle faults being the southern, western, and northern faces. The energy of the somewhat smaller Benioff earthquakes is likewise diluted over a relatively large area. And the magnitude used to generate that wave is only about 7.5, as opposed to a magnitude-9 earthquake off the coast. 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. The Woods Lake Fault, running past Lake Chaplain, corresponds closest to the mapped position of the southern end of Cheney's Mount Vernon Fault. This is only one of a series of active large crustal faults in the Puget Lowland. 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. Folding and faulting has exposed these basalts in some places (black areas in diagram); the intervening basins have been filled by various sedimentary formations, some of which have been subsequently uplifted. $30-$33/hr Electrician Job at University of Puget Sound [207] North of the RMFZ it follows a topographical lineament that can be traced to Rockport (on Hwy. A magnitude 7.1 earthquake in the Tacoma Fault Zone A - USGS The Pacific Northwest Seismic Network (PNSN) reported at least three earthquakes within the past few days. ), 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. [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. There are other tsunami scenarios that are not accounted for in these maps, such as tsunamis caused by . Mapping from the Pacific Northwest Seismic Network shows that the bulk of the earthquakes in western Washington are concentrated in four places: in two narrow zones under Mt. Interpretation of the eastern part of the Tacoma Fault is not entirely settled. ), and headed for the definitely active Saint Helens Zone; this appears to be a large-scale structure. 2-5 Cruises Age 60s. On the east, the Devils Mountain Fault connects with the south striking Darrington Fault (not shown) which runs to the OWL, and the Southern Whidbey Island Fault extends via the Rattlesnake Mountain Fault Zone (dashed line) to the OWL. 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. [38] These earthquakes probably caused tsunamis, and several nearby locations have evidence of tsunamis not correlated with other known quakes. Although the southwest striking Canyon River Fault is not seen to directly connect with the Saddle Mountain faults, they are in general alignment, and both occur in a similar context of Miocene faulting (where Crescent Formation strata has been uplifted by the Olympics) and a linear aeromagnetic anomaly. Get directions. The passive roof duplex model of Brocher et al. 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. Click a second point on the map, this will be the right side of the cross-section. [130] This is likely not coincidental, as it appears that the Tacoma and Seattle faults converge at depth (see diagram above) in a way that northsouth compression tends to force the Seattle Uplift up, resulting in dip-slip movement on both fault zones. . Read More. Next to a 4-6 lines highways with 90db noise and cancerous pollution. [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). Study: Tsunami from Cascadia mega-quake would submerge Puget Sound The WRZ and SHZ are associated with the southern Washington Cascades conductor (SWCC), a formation of enhanced electrical conductivity[194] lying roughly between Riffe Lake and Mounts St. Helens, Adams, and Rainier, with a lobe extending north (outlined in yellow, right). Seattle Fault Zone in Central Puget Sound Washington Military Department FEMA Emergency Management Division . Publication Year: 2010: Title: A magnitude 7.1 earthquake in the Tacoma Fault Zone A plausible scenario for the southern Puget Sound region, Washington: DOI: 10.3133/fs20103023: Authors: [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. New tsunami simulation predicts flooding on Olympic Peninsula | Tacoma [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). 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. The Seattle Fault is the most studied of the regional faults, which has led to several models of its structure, which may also be relevant to other faults. 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. Sail Date . [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. William Pietsch - Distribution Grid Managment Analyst - Puget Sound [61], North of Everett is an area of parallel ridges and stream drainages oriented approximately NW-SE, evident even on non-geological maps. Simply put, the basement rock on the west side of Puget Sound does not match the basement rock on the east side. 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. While these models vary in some details, both indicate that the Seattle Fault itself is capable of a magnitude 7.5 earthquake. [73] The presence of detritus from the Idaho Batholith[72] indicates a former location closer to southern Idaho. But their significance to the Puget Sound area is unknown. [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. ISNS Ch 5 Flashcards | Quizlet These faults are: the Kopiah Fault (note the curious curve), Newaukum Fault, Coal Creek Fault, and three other unnamed faults. The 1949, 1965, and 2001 Puget Sound earthquakes were the result of _____ fault movement within the Juan de Fuca plate. [122] This trend extends further north where the Pleasant Harbor lineament appears to terminate other westward extensions of the SFZ. [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. The lowest exposed strata of Tiger Mountain, the mid-Eocene marine sediments of the Raging River formation, may be correlative with the SWCC. OLYMPIA, Wash. - A 9. Strands of the east-striking Devils Mountain Fault cross the northern tip of Whidbey Island at Dugualla Bay and north side of Ault Field (Whidbey Island Naval Air Station). 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? See. [206] This line may also mark the northwestern boundary of the SWCC. 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. A 2001 study[148] using high-resolution seismic tomography questioned its existence. Faults running on the Snohomish County-Skagit County line and between Port Townsend and Whidbey Island point toward Vancouver Island. It follows the Bainbridge Island ferry route east under Puget Sound and the route of Interstate 90 toward, and possibly beyond, the Cascade Mountains. [95], (Rattlesnake Mountain Fault Zone not included in QFFDB. [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. [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. The DotySalzer Creek Fault does not fully fit the regional pattern of basins and uplifts bounded by faults described above. 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. 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. In the angle between these is located the minor Lincoln Creek uplift, the Doty Hills, and, further west, an impressive chunk of Crescent basalt. (Their model of the Black Hills Uplift is analogous with their "wedge" model of the Seattle Uplift, discussed above, but in the opposite direction. [51] And in between these two the Strawberry Point Fault (SPF) skirts the south side of Ault Field, splits into various strands that bracket Strawberry Point, and then disappear (possibly ending) under the delta of the Skagit River. Cheney also mapped the Lake Chaplain Fault, parallel and just east of the MVF, from Lake Chaplain to Granite Falls. Tacoma, WA. [112] But if the Seattle Fault should break in conjunction with other faults (discussed above), considerably more energy would be released, on the order of ~M 8. There's a one-in-10 chance that the next . [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. The last major earthquake on the Seattle Fault occurred around 1,100 years ago, shifting the landscape in Puget Sound. Glacially deposited and shaped fill covers most of the lower elevations of Puget Sound. Please follow the steps below: . 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