[Paper No. [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. - Read More Expert Puts Turkey, Syria Quake into Perspective | FOX 13 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. As all of these are thrust and reverse faults, they probably result from northeast directed regional compression. Somewhere between Puget Sound and Cascades foothills these two geological provinces come into contact. ), 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". [71], These faults cut through the Western Mlange Belt (WMB; blue area in map), exposed from North Bend (on Interstate 90) to Mount Vernon. 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. to the north, past Lummi Island is contrary to the prevailing consensus that the DMF is not offset. 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. 09 Feb 2023 03:01:00 Glacially deposited and shaped fill covers most of the lower elevations of Puget Sound. [125] While some coherency is developing, the story is not complete: identified faults do not yet account for much of the region's seismicity. [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. [118], Studies of the Seattle Fault west of Bremerton have revealed a complexity of geological structure and faulting. 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. 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. However, there are indications that the fault is segmented, which might limit rupturing and earthquake magnitude.[36]. These lineaments have been associated with possible zones of faulting in the crust and subducting plate.[212]. 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). normal. Saint Helens and Mt. The last large event was in 1700, but there is a 37 percent chance of an 7.1+ in the next 50 years. 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. Nurse Recruiter at VA Puget Sound health care, 206-764-2487. 10+ Cruises Age 2020s. 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. 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). Review for American Constellation to U.S.A. chatuga. 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. The Seattle Fault, a zone of east-west thrust faults under the Puget Sound and Seattle, last ruptured in a magnitude-7.0 to -7.5 earthquake about 1,100 years ago. This formation, up to 15km thick, is largely buried (from one to ten kilometers deep), and known mainly by magnetotellurics and other geophysical methods. [68] Both of these faults (and some others) appear to terminate against the left-lateral Sultan River Fault at the western margin of the NNE-striking Cherry Creek Fault Zone (CCFZ; see next section). 39 earthquakes in the past 365 days. Posted: 12 days ago. Most people in the United States know just one fault line by name: the San Andreas, which runs nearly the length of California and is perpetually rumored to be on the verge of unleashing "the. The Seattle Fault is a zone of complex thrust and reverse faults between lines E and F on the map up to 7km wide and over 70km long that delineates the north edge of the Seattle Uplift. Puget Sound Lidar Consortium Finding faults scarp(n). These are usually fairly short, and not believed to be significantly seismogenic. 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]. [216], An Everett Fault, running east-northeast along the bluffs between Mukilteo and Everett that is, east of the SWIF and at the southern edge of the Everett Basin has been claimed, but this does not appear to have been corroborated.[217]. [88] (See the adjacent map. Seven times in the past 3,500 years, the CSZ has buckled and fractured to produce an earthquake so massive that it left a mark in the geologic record. Washington's fault lines tend to sweep east-west. [106] There is an intriguing view from Stanley, Villaseor & Benz (1999) (see Fig. 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. [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. For the following reviews the primary source of information is the U.S. Geological Survey's Quaternary fault and fold database (QFFDB), which includes details of discovery, a technical description, and bibliography for each fault; a specific link is provided (where available) at the end of each section. 2-5 Cruises Age 60s. 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. These include (from north to south, see map) the: Devils Mountain Fault Strawberry Point and Utsalady Point faults Southern Whidbey Island Fault (SWIF) 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. 64, on-line) that the edge of the Crescent Formation offsets west along the Seattle Fault, with the Seattle Basin resulting from a gap between the main part of Siletiza and a northern block that has broken away. These include the: Southern Whidbey Island Fault (SWIF) Seattle Fault Devils Mountain Fault Strawberry Point fault Utsalady Point fault Calawah fault Barnes Creek 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 history and capabilities of the Frigid Creek Fault are not known. Tacoma's Gain is Seattle's Pain. (2001),[111] relying on seismic tomography data from the "Seismic Hazards Investigation in Puget Sound" (SHIPS) experiment, retains the thrusting slab and master ramp concepts, but interprets the Tacoma fault as a reverse fault (or back thrust) that dips north towards the south dipping Seattle fault (see diagram); as a result the Seattle Uplift is being popped up like a horst. [45] The Leech River Fault has been identified as the northern edge of the Crescent Formation (aka Metchosin Formation, part of the Siletzia terrane that underlies much of western Washington and Oregon). 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. [180], That Olympia and the south Sound are at risk of major earthquakes is shown by evidence of subsidence at several locations in southern Puget Sound some 1100 years ago. Nor does this uplift delineate any significant basin between it and the Devils Mountain Fault. King County Emergency Management. 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. Subsidence dated to between AD 1445 and 1655 has been reported in Mud Bay (just west of Olympia). (Enter only one word per blank.) [56] But detailed mapping just past the intersection shows only a complex and confused pattern of faulting, with no indication that there is, or is not, through-going faulting. (1997), while observing the "remarkable straight boundaries that we interpret as evidence of structural control",[171] refrained from calling this structure a fault. [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. 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. [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. This map shows areas of seismic risk from high (red) to low (grayish-green). The Doty fault particularly seems to have gained prominence with geologists since it was associated with an aeromagnetic anomaly,[184] and a report in 2000 credited it capable of a magnitude 6.7 to 7.2 earthquake. Simply put, the basement rock on the west side of Puget Sound does not match the basement rock on the east side. 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a new perspective on seismic hazards in Washington using aeromagnetic data", "Constraints on surface deformation in the Seattle, WA, urban corridor from satellite radar interferometry time-series analysis", "Crustal Structure and Earthquake Hazards of the Subduction Zone in Southwestern British Columbia and Western Washington", "Late Mesozoic or Early Tertiary Melanges in the Western Cascades of Washington", "Seismotectonic map of the Puget Sound region, Washington", "Distribution of late Cenozoic volcanic vents in the Cascade Range: Volcanic arc segmentation and regional tectonic considerations", "Geologic map of the Wildcat Lake 7.5' quadrangle, Kitsap and Mason Counties, Washington", "Fault scarp detection beneath dense vegetation cover: airborne LIDAR mapping of the Seattle Fault Zone, Bainbridge Island, Washington State", 10.1130/1052-5173(2003)13<0004:HLTOTP>2.0.CO;2, "Structural variation along the Devil's Mountain fault zone, northwestern Washington", 10.1130/0091-7613(1980)8<15:SOTCVC>2.0.CO;2, "Fault number 572, Southern Whidbey Island Fault", "Active shortening of the Cascadia forearc and implications for seismic hazards of the Puget Lowland", "Active tectonics of the Seattle fault and central Puget Sound, Washington Implications for earthquake hazards", 10.1130/0016-7606(1999)111<1042:ATOTSF>2.3.CO;2, "Evidence for Late Holocene Earthquakes on the Utsalady Point Fault, Northern Puget Lowland, Washington", 10.1130/0091-7613(1994)022<0071:OAEOTS>2.3.CO;2, "The southern Whidbey Island fault An active structure in the Puget Lowland, Washington", 10.1130/0016-7606(1996)108<0334:TSWIFA>2.3.CO;2, "Late Holocene displacement on the Southern Whidbey Island fault zone, northern Puget lowland", "The Tahuya Lineament: Southwestern Extension of the Seattle Fault? [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. [2] All this is at risk of earthquakes from three sources:[3]. 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. 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. 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? The Cascadia Fault is 620 miles long off the coast of Washington and British Columbia. 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. 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). Combined with continued aggressive electric conservation efforts, Energize . About 1,100 years ago, a major earthquake rocked Puget Sound, suddenly shooting what is now Restoration Point on Bainbridge Island up about 23 feet while Seattle 's West Point sunk more than. [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. 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. 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. Aeromagnetic surveys,[13] seismic tomography,[14] and other studies have also contributed to locating and understanding these faults. It aligns with the West Coast fault and Queen Charlotte Fault system of strike-slip fault zones (similar to the San Andreas Fault in California) on the west side of Vancouver Island, but does not itself show any significant or through-going strike-slip movement. Some of these faults possibly developed in the Mesozoic, when these deposits were in the accretionary wedge;[72] the cross-cutting NE and NNE-striking faults that form the various basins resulted from a subsequent change to transtension. 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. And since those models for the Seattle Fault were published, there've actually been many more Puget Sound faults discovered. 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. 1958 and Geologic Map GM-34 for details.). It follows the Bainbridge Island ferry route east under Puget Sound and the route of Interstate 90 toward, and possibly beyond, the Cascade Mountains.