Average High School Football Player Squat, Top 10 Biggest Cricket Ground In The World, Articles F

[82] Aeromagnetic anomaly maps (USGS OFR 99-514). 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. There is evidence that the Tacoma Fault connects with the White River River Fault (WRF) via the EPZ and Federal Way, under the Muckleshoot Basin (see map),[137] and thence to the Naches River Fault. [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. Energy builds up as elastic strain in rocks. 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). 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). [2] All this is at risk of earthquakes from three sources:[3]. Earthquake - Emergency Management | seattle.gov [42] Marine seismic reflection surveys show it striking northwest across the eastern end of the Strait of Juan de Fuca. Despite not having active plate tectonics, the eastern United States still experiences earthquakes. [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. The Seattle Fault crosses east-west through Puget Sound and downtown Seattle. [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. Contact Us | VA Puget Sound Health Care | Veterans Affairs [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). Methane Plume Emissions Associated With Puget Sound Faults in the [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. [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. Not until 2001 was it identified as a fault zone,[12] and only in 2004 did trenching reveal Holocene activity. [71], These faults cut through the Western Mlange Belt (WMB; blue area in map), exposed from North Bend (on Interstate 90) to Mount Vernon. In this model the Tacoma fault zone is primarily the result of local adjustments as the slab bends upward at the bottom of the ramp. [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. This boundary would be the contact where northward movement of the basement rock of the Puget Lowland against the Olympic Peninsula is accommodated; it would be expected to be a significant seismological zone. Olympia VA Clinic at VA Puget Sound health care, 253-583-2621 Housing: The Puget Sound had the largest increase in population per 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. Scientists look for answers in methane bubbles rising from bottom of [122] This trend extends further north where the Pleasant Harbor lineament appears to terminate other westward extensions of the SFZ. The Earthquake That Will Devastate the Pacific Northwest [213] Seismicity sometimes occurs in zones, such as has been observed under Mercer Island, or from downtown Seattle towards Kirkland[214] but whether particular zones reflect undiscovered faults, or might be the source of damaging earthquakes, is generally unknown. [43] Just south of Victoria, British Columbia it intersects the west-striking Devils Mountain Fault (reviewed above), and either merges with it,[44] or crosses (and possibly truncates) it to connect with the Leech River Fault. These are usually fairly short, and not believed to be significantly seismogenic. ), and headed for the definitely active Saint Helens Zone; this appears to be a large-scale structure. One animation shows the expected path of a Puget Sound tsunami generated by a quake on the Seattle Fault. PSLC--finding faults - University of Washington [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. [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. [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 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. [57] Mapping of areas further east that might clarify the pattern is not currently planned. [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). [118], Studies of the Seattle Fault west of Bremerton have revealed a complexity of geological structure and faulting. Display Faults. The Seattle fault zone is where the forward edge of the slab, coming to the top of the ramp, breaks and slips into the Seattle Basin. [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. [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. Following a mega quake on the Cascadia fault, simulations show that the tiny town of La Push would get hit first by a tsunami, 10 minutes after shaking started. [32] And it is suggested that the Great Seattle Quake of approximately 1,100 years ago, and other coseismic events in southern Puget Sound around that time, were a single event that affected this entire block, with a magnitude of around 8, possibly triggered by an earthquake deeper in the crust.[33]. [219] Various other faults in the North Cascades are older (being offset by the Straight Creek Fault) and are unrelated to the faults in Puget Sound. New gravity data provide information [abstract]", "Fault locking, block rotation and crustal deformation in the Pacific Northwest", "The Everett fault: a newly discovered late Quaternary fault in north-central Puget Sound, Washington [abstract]", "Late Holocene earthquakes on the Toe Jam Hill fault, Seattle fault zone, Bainbridge Island, Washington", "Field and laboratory data from an earthquake history study of scarps in the hanging wall of the Tacoma fault, Mason and Pierce Counties, Washington", "Three-dimensional velocity structure of Siletzia and other accreted terranes in the Cascadia forearc of Washington", "Geologic map of the Skokomish Valley and Union 7.5-minute quadrangles, Mason County, Washington", "Supplement to Geologic Maps of the Lilliwaup, Skokomish Valley, and Union 7.5-minute Quadrangles, Mason County, Washington Geologic Setting and Development Around the Great Bend of Hood Canal", "Geologic map of the Hoodsport 7.5-minute quadrangle, Mason County, Washington", "Geologic map of the Brinnon 7.5-minute quadrangle, Jefferson and Kitsap Counties, Washington", "Geologic map of the Seabeck and Poulsbo 7.5-minute quadrangles, Kitsap and Jefferson Counties, Washington", "Evidence for earthquake-induced subsidence ~1100 yr ago in coastal marshes of southern Puget Sound, Washington", 10.1130/0016-7606(2001)113<1299:EFEISA>2.0.CO;2, "Holocene fault scarps and shallow magnetic anomalies along the Southern Whidbey Island Fault Zone near Woodinville, Washington", "Finding concealed active faults: Extending the southern Whidbey Island fault across the Puget Lowland, Washington", "Holocene fault scarps near Tacoma, Washington, USA", "The Catfish Lake Scarp, Allyn, Washington: Preliminary Field Data and Implications for Earthquake Hazards posed by the Tacoma Fault", "Seismic Amplification within the Seattle Basin, Washington State: Insights from SHIPS Seismic Tomography Experiments", "Tectonics and Conductivity Structures in the Southern Washington Cascades", "Analysis of Deep Seismic Reflection and Other Data From the Southern Washington Cascades", "Tectonics and Seismicity of the Southern Washington Cascade Range", "Subduction zone and crustal dynamics of western Washington: A tectonic model for earthquake hazards evaluation", 10.1130/0016-7606(1994)106<0217:lmapet>2.3.co;2, "Geologic map of the Snoqualmie Pass 60 minute by 30 minute quadrangle, Washington", "Subsurface Geometry and Evolution of the Seattle Fault Zone and the Seattle Basin, Washington", "Rupture models for the A.D. 900930 Seattle fault earthquake from uplifted shorelines", "Stratigraphy of Eocene rocks in a part of King County, Washington", "Geologic map of Washington Southwest Quadrant", "Geologic Map of the East Olympia 7.5-minute Quadrangle, Thurston County, Washington", "Field data for a trench on the Canyon River fault, southeast Olympic Mountains, Washington", "Crustal Extension at Mount St. Helens, Washington", "Final Technical Report: Two Post-Glavial Earthquakes on the Saddle Mountain West Fault, southeastern Olympic Peninsula, Washington", "Earthquake scenario and probabilistic ground shaking maps for the Portland, Oregon, metropolitan area", "Bedrock Geologic Map of the Seattle 30' by 60' Quadrangle, Washington", Preliminary Atlas of Active Shallow Tectonic Deformation in the Puget Lowland, Washington (USGS Open-File Report 2010-1149). 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. 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. Seattle Fault Zone in Central Puget Sound Washington Military Department FEMA Emergency Management Division . 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. It is uncertain how these faults relate to the structure, and whether they are deep-seated faults, or fractures due to bending of the shallow crust. 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. 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. Analysis of seismic profiles extending 50 km across the Puget Lowland from Lake Washington to Hood Canal indicates . The Cascadia Fault is 620 miles long off the coast of Washington and British Columbia. [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. The map is from a 2007 report (click here to download) on seismic design categories in Washington. Today's Earthquakes in Olympic Peninsula, Washington The Devils Mountain Fault (DMF) runs about 125km (75 miles) from the town of Darrington in the Cascade foothills due west to the northern tip of Whidbey Island, and on towards Victoria, British Columbia, where the DMF is believed to join the Leech River fault system at the southern end of Vancouver Island. Several possible explanations of the enhanced conductivity have been considered; Eocene marine sediments containing brine are most likely (. Cheney also mapped the Lake Chaplain Fault, parallel and just east of the MVF, from Lake Chaplain to Granite Falls. [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]. 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: Geologic Hazard Maps | WA - DNR See Snavely et al. Tobin says offshore faults tend to cause bigger earthquakes and are a larger tsunami risk. Geographic boundaries of Puget Sound and the Salish Sea The Doty Fault appears to terminate against, or possibly merge with, the Salzer Creek Fault at Chehalis; the Salzer Creek Fault is traced another seven miles east of Chehalis. [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. The San Juan Island and Leach River faults crossing the southern end of Vancouver Island are significant and undoubtedly connected with the DarringtonDevils Mountain and Southern Whidbey Island faults, and certainly of particular interest to the residents of Victoria, B.C. The length of the Doty Fault is problematical: the report in 2000 gave it as 65km (40 miles), but without comment or citation. [107], The Seattle Fault was first identified in 1965[108] but not documented as an active fault until 1992 with a set of five articles establishing that about 1100 years ago (AD 900930) an earthquake of magnitude 7+ uplifted Restoration Point and Alki Point, dropped West Point (the three white triangles in the Seattle Basin on the map), caused rockslides in the Olympics, landslides into Lake Washington, and a tsunami on Puget Sound. [44] The significance of this whether the edge of the Crescent Formation (and implicitly of the Siletz terrane) turns southward (discussed below), or the metamorphic basement is supplanted here by other volcanic rock is not known. The mapped surface traces are only 5km long, but LIDAR-derived imagery shows longer lineaments, with the traces cutting Holocene alluvial traces. (A) Map of the Seattle fault zone (SFZ) in the central Puget Sound [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. A Lofall Fault has been reported on the basis of marine seismic reflection surveying,[216] but has not been confirmed by trenching. 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. 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. 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? [218] This would pose significantly greater seismic hazard than currently recognized, especially as the White River Fault is believed to connect with the Naches River Fault that extends along Highway 410 on the east side of the Cascades towards Yakima. [79] It is deemed a "major active or potentially active" structure. 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. 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. The Straight Creek Fault is a major structure in the North Cascades, but has not been active for over 30 million years. 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). PNSN Recent Events | Pacific Northwest Seismic Network The Doty fault has been mapped from the north side of the Chehalis airport due west to the old logging town of Doty (due north of Pe Ell), paralleled most of that distance by its twin, the Salzer Creek Fault, about half a mile to the north. This fault produced a large earthquake that left a geologic record of surface offsets about 1100 years ago. North Olympic Peninsula VA Clinic at VA Puget Sound health care, 360-565-7420. 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. Posted: 12 days ago. They run . [95], (Rattlesnake Mountain Fault Zone not included in QFFDB. Aeromagnetic surveys,[13] seismic tomography,[14] and other studies have also contributed to locating and understanding these faults. This structure is shown in the gravitational mapping of 1965, but without comment. TTY Relay 711. "[31] More particularly, the concentration of seismicity under Puget Sound south of the Seattle Fault is attributed to uplift of that block, bounded by the Seattle, Tacoma, and Dewatto faults on the north, south, and west (the eastern boundary is not determined), creating the Seattle Uplift. normal. It has been speculated that the OS might connect with the seismically active Saint Helens Zone (discussed below), which would imply that the OS is both locked and being stressed, raising the possibility of a major earthquake. Black squares are urban sewer outfalls, which don't match the bubble plumes' locations. Ancient quake and tsunami in Puget Sound shake researchers 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. 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). An earthquake occurs along a south-moving fault. 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. [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. [87], Rattlesnake Mountain is a prominent NNW trending ridge just west of North Bend (about 25 miles east of Seattle). 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. The magnitude-4.0 earthquake that rattled people awake across the Puget Sound region last Wednesday probably struck on the western edge of the Seattle Fault, according to geologists. Both of these are dip-slip (vertical) faults; the block between them has been popped up by compressive forces. 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. 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. For information about the Energize Eastside project, . The question of where on Puget Sound the line would ultimately end was intentionally left open, and the region's fledgling cities began competing furiously for the good fortune of a major railroad terminus. King County Emergency News. Saint Helens and Mt. In the angle between these is located the minor Lincoln Creek uplift, the Doty Hills, and, further west, an impressive chunk of Crescent basalt. Fault lines in the New Madrid seismic zone are being mapped, thanks in part to . 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. [209] Between the Cherry Creek and parallel Tokul Creek faults is a contact between formations of the Western Melange Belt. A principal finding is that "[c]rustal seismicity in the southern Puget Sound region appears to be controlled by a key block of Crescent Formation occurring just south of the Seattle fault. . Active tectonics of the Seattle fault and central Puget sound Recent EQ List At the edge of this older rock is the Rogers Belt, a geologically interesting zone running from the area of Sultan (due east of Everett) to Mount Vernon (just north of the bend in the Devils Mountain Fault). But the western segment the Devils Mountain Fault has left-lateral movement. Earthquakes and Faults | WA - DNR Doubts on the connectivity of these faults led to abandonment of this name in 1986[65] when Cheney mapped the Mount Vernon fault (MVF) from near Sultan northwest past Lummi Island (west side of Bellingham Bay, visible at the top of the map), crossing the Devils Mountain Fault (DMF, part of the DarringtonDevils Mountain Fault Zone) near Mount Vernon. This is an important observation because the Strawberry Point, Utsalady Point, Southern Whidbey Island, and various other unnamed faults lying between the DDMFZ and the OWL all of which converge at the western end of the DDMFZ seem to be intermediate versions of the DDMFZ.[34]. The lowest exposed strata of Tiger Mountain, the mid-Eocene marine sediments of the Raging River formation, may be correlative with the SWCC. [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. ISNS Ch 5 Flashcards | Quizlet [51] But. 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. 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. 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. Scientists Search for New Faults in Puget Sound If entirely analogous, then "roof duplex" might also apply, and the Olympia Fault would be a reverse fault similar to the Tacoma Fault. This map shows areas of seismic risk from high (red) to low (grayish-green). Though the Olympia Structure (a suspected fault) runs towards the SHZ, and delineates the northern edge of an exposed section of the Crescent Formation, it appears to be an upper crustal fold, part of a pattern of folding that extends southeast to cross the Columbia River near The Dalles, and unrelated to the mid and lower crustal SHZ. Gonzalez: That Seattle Fault tsunami has been modeled by others. [29] This prospect is especially intriguing as a possible explanation of a cluster of seismic events around 1100 years ago.[30]. 1 earthquake in the past 7 days. (1997), while observing the "remarkable straight boundaries that we interpret as evidence of structural control",[171] refrained from calling this structure a fault. If so, this would be a major fault system (over 185km long), connecting the Puget Lowland with the Yakima Fold Belt on the other side of the Cascades, with possible implications for both the OlympicWallowa Lineament (which it parallels) and geological structure south of the OWL. 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. There are numerous other faults (or fault zones) in the Puget Lowland, and around its edges, sketchily studied and largely unnamed. 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.