[62] These ridges (part of a broader regional pattern that reflects the roots of the former Calkins Range[63]) are formed of sediments that collected in the Everett basin during the Eocene, and were subsequently folded by northeast-directed compression against the older Cretaceous and Jurassic rock to the east that bound the Puget Lowland. [102] Or the Crescent margin may simply (and quietly) just run south-southeast under Seattle to the WRZ. Based on this and geophysical anomalies it was inferred that there is a major, active strike-slip fault zone running from the south end of Hood Canal, up Dabob Bay, and continuing north on land. Puget Sound Lidar Consortium Finding faults scarp(n). 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. [51] This map is useful in showing the location and approximate length of faults but does not provide the impact an earthquake from a fault could have on the area surrounding. Puget Sound, Washington has had: (M1.5 or greater) 0 earthquakes in the past 24 hours. Since 2000 studies of LIDAR and high-resolution aeromagnetic data have identified scarps near Woodinville which trenching has confirmed to be tectonically derived and geologically recent. Movement on the southern segment of the DDMFZ that converges with the SCF the Darrington Fault was, as on the SCF itself, right-lateral. 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. [95], (Rattlesnake Mountain Fault Zone not included in QFFDB. 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. 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. Here the main strand on the western edge merges with the Sultan River Fault under the Sultan River. This pocket is catching a stream of terranes (crustal blocks about 20 to 30km thick[18]) which the Pacific plate is pushing up the western edge of North America, and in the process imparting a bit of clockwise rotation to southwestern Washington and most of Oregon; the result has been characterized as a train wreck. The most striking concentrations of mid-crustal seismicity in western Washington outside of Puget Sound are the Saint Helens Zone (SHZ) and Western Rainier Zone (WRZ) at the southern edge of the Puget Lowland (see seismicity map, right). Cluster of earthquakes in Puget Sound considered 'normal', earthquake researchers say. [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. On the north is the HelenaHaystack mlange (HH mlange, purple in the diagram at right), on the south the Western and Eastern mlange belts (WEMB, blue). Gonzalez: That Seattle Fault tsunami has been modeled by others. 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? [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. [140] Recent geophysical modeling suggests that the Dewatto lineament is the expression of a blind (concealed), low-angle, east-dipping thrust fault, named the Dewatto fault. One animation shows the expected path of a Puget Sound tsunami generated by a quake on the Seattle Fault. 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). [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]. Posted: 12 days ago. 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). The Pacific Northwest Seismic Network (PNSN) reported at least three earthquakes within the past few days. 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, the SWCC is relatively shallow (no more than 15 km deep), and likely is draped over pre-Tertiary bedrock. It stands out in regard of its eastwest orientation, depth to bedrock, and hazard to an urban population center. 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. [66] This is located on a topographical lineament that aligns with Mount Vernon to the north, and, to the south, the city of Granite Falls and Lake Chaplain (just north of Sultan). This is the Dewatto lineament, believed to result from an east-dipping low-angle thrust fault where the western flank of the Seattle Uplift has been pushed into the northwestern corner of the Tacoma Basin. A Seattle Fault quake could be as large as M7.5,160 but less than M7.0 is more probable. 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. normal. Deep quakes are the most common large earthquakes that occur in the Puget Sound region. [39] On the basis of marine seismic reflection surveying in the Strait of Juan de Fuca it has been suggested that the DMF, SPF, and UPF are structurally connected (at least in the segment crossing Whidbey Island). [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. Earthquakes occur nearly every day in Washington. Fault lines in the New Madrid seismic zone are being mapped, thanks in part to . And like the SCF, strike-slip motion died out between 44 and 41 MA (due to plutonic intrusions). and Fault Location. Part of the Snohomish River Delta between Everett and Marysville could get nearly 6 feet, and Seattle's Harbor Island could be inundated with nearly 4 feet of water. The study was. 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]. In the map above these are represented by the pair of dotted lines at the lower right. [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. 48), along the edge of a formation known as the Southern Washington Cascades Conductor. 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 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. [155] North of the Seattle Fault accommodation of regional movement may be along the northwest-striking Dabob Bay Fault Zone. [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. [206] This line may also mark the northwestern boundary of the SWCC. Tobin says offshore faults tend to cause bigger earthquakes and are a larger tsunami risk. 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 Devils Mountain Fault separates two similar but distinctive ensembles of Mesozoic (pre-Tertiary, before the dinosaurs died) or older rock. Puget Sound Energy Maps and Records Non-Disclosure Agreement: (NDA ONLY) ko ru zh es vi hi: PSE Map Request Form and Non-Disclosure Agreement: 07/29/2022: Somewhere between Puget Sound and Cascades foothills these two geological provinces come into contact. - Read More Expert Puts Turkey, Syria Quake into Perspective | FOX 13 Other similar lineaments (such as from Astoria to Glacier Peak) align with various topographical features and changes in fault orientation. One study compared the relative elevation of two marshes on opposite sides of Whidbey Island, and determined that approximately 3,000 years ago an earthquake of M 6.57.0 caused 1 to 2 meters of uplift. ", Because of the geometry of the SWIF and the Kingston arch, the "uplift of unknown origin" between them is smaller, and the fault separating the uplift from the arch (the Lofall Fault, discovered relatively recently by, Strictly speaking the southern edge of the Black Hills Uplift would be the southeast striking Scammon Creek Fault that converges with the east striking Doty Fault at Chehalis. The discovery was an alarm bell for engineers and emergency planners. "[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. 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). 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. 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. However, there are indications that the fault is segmented, which might limit rupturing and earthquake magnitude.[36]. (E.g., the Olympia Fault is aligned with and appears to be the northernmost member of a set of faults between Olympia and Chehalis that may extend to the Columbia River, and there has been a suggestion that the Tacoma Fault may connect with the White RiverNaches River fault on the east side of the Cascades.[24]). It therefore seems reasonable that the rest of the SWIF (and its apparent extension, the RMFZ) follows the Coast RangeCascade contact, and (these faults being active) constitutes the CRBF. [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. 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. Saint Helens and Mt. [114] An early view was that "the Seattle Fault appears to be truncated by the Hood Canal fault and does not extend into the Olympic Mountains". Yet the former is only the first of at least six more parallel southeast striking faults, which do cross the Salzer Creek Fault.