Crockpot Ground Beef Tacos, George Jenkins High School Schedule, Velocity Community Credit Union Shared Branches, Why Is My Canon Rebel T6 Taking Blurry Pictures, Articles F

Seismic waves transmit the energy In some places, such as along the South Fork of the Stillaguamish River between Arlington and Granite Falls, there are also contrasting geological contacts. 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. The last major earthquake on the Seattle Fault occurred around 1,100 years ago, shifting the landscape in Puget Sound. San Juan Island hopping on the Puget Sound, WA. Black lines show the South Whidbey Island Fault Zone, the . 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. The fault type is subducting. Rainier is offset because the faults are deep and the conduits do not rise quite vertically.) Sail Date: October 2022 . It follows the Bainbridge Island ferry route east under Puget Sound and the route of Interstate 90 toward, and possibly beyond, the Cascade Mountains. Large plumes of methane bubbles have been discovered throughout the waters of Puget Sound prompting questions about the Puget Sound food web, studies of earthquake faults and climate-change research. But today, after 131 years of statehood, residents of this region still don't know if they have a legal right to walk across a privately . [78] It is projected to extend past Lake Chaplain, and perhaps to the east end of Mount Pilchuck. [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. For information about the Energize Eastside project, . Somewhere between Puget Sound and Cascades foothills these two geological provinces come into contact. Despite not having active plate tectonics, the eastern United States still experiences earthquakes. Black lines show the South Whidbey Island Fault Zone, the Seattle Fault Zone and the Tacoma. Not until 2001 was it identified as a fault zone,[12] and only in 2004 did trenching reveal Holocene activity. [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. [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". Its capable magnitude is a megathrust quake exceeding 9.0. [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. 6 earthquakes in the past 7 days. Most of these "faults" are actually zones of complex faulting at the boundaries between sedimentary basins (synclines, "") and crustal uplifts (anticlines, ""). [87], Rattlesnake Mountain is a prominent NNW trending ridge just west of North Bend (about 25 miles east of Seattle). Western Washington lies over the Cascadia subduction zone, where the Juan de Fuca Plate is subducting towards the east (see diagram, right). Energy builds up as elastic strain in rocks. In particular, to the southeast of Mount St. Helens and Mount Rainier they reflect a regional pattern of NNW oriented faulting, including the Entiat Fault in the North Cascades and the Portland Hills and related faults around Portland (see QFFDB fault map). 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? Plot Type: X-Section Depth Cumulative # Mag-Time. ), and headed for the definitely active Saint Helens Zone; this appears to be a large-scale structure. This map of Puget Sound shows the location of the methane plumes (yellow and white circles) detected along the ship's path (purple). These faults are: the Kopiah Fault (note the curious curve), Newaukum Fault, Coal Creek Fault, and three other unnamed faults. [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). [125] While some coherency is developing, the story is not complete: identified faults do not yet account for much of the region's seismicity. [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]. Aeromagnetic surveys,[13] seismic tomography,[14] and other studies have also contributed to locating and understanding these faults. [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). The Straight Creek Fault is a major structure in the North Cascades, but has not been active for over 30 million years. 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. 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. Locations of some previously mapped faults have been adjusted on the latest map. Read More. [73] The presence of detritus from the Idaho Batholith[72] indicates a former location closer to southern Idaho. 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). (A tsunami generated by a quake on the offshore Cascadia Subduction Zone would be . Accommodation of strain (displacement) between the Seattle Fault and the Saddle Mountain deformation zone is likely distributed across the more pliable sediments of the Dewatto Basin; this, and the greater depth to the Crescent Formation, may account for the subdued expression of the Seattle Fault west of Green Mountain. In the map above these are represented by the pair of dotted lines at the lower right. 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. 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. When the applied stresses become overpowering, the rocks at the fault rupture. The map is from a 2007 report (click here to download) on seismic design categories in Washington. Geologic map of northwestern Washington (GM-50). slope, need not be high. [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. 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). These lineaments have been associated with possible zones of faulting in the crust and subducting plate.[212]. [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. [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]. Can be formed by differential erosion of adjacent hard and soft rock; by localized erosion, for example at the edge of a river terrace; by movement of a landslide; or by a shallow earthquake that is large enough to break the Earth's surface. Seismic tomography studies show a change in seismic velocities across the northern end of the SWIF, suggesting that this is also part of the Coast RangeCascade contact. Other similar rock has been found at the Rimrock Lake Inlier (bottom of diagram), in the San Juan Islands, and in the Pacific Coast Complex along the West Coast Fault on the west side of Vancouver Island. [115] This seems reasonable enough, as Hood Canal is a prominent physiographic boundary between the Olympic Mountains and Puget Lowlands, and believed to be the location of a major fault. Geologic Map. [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. [57] Mapping of areas further east that might clarify the pattern is not currently planned. [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. 48), along the edge of a formation known as the Southern Washington Cascades Conductor. fault Which of the following statements best describes elastic-rebound theory? [11] Marine seismic reflection surveys on Puget Sound where it cuts across the various faults have provided cross-sectional views of the structure of some of these faults, and an intense, wide-area combined on-shore/off-shore study in 1998 (Seismic Hazards Investigation in Puget Sound, or SHIPS)[12] resulted in a three-dimensional model of much of the subsurface geometry. [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. 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. [153] For these reasons this is now a questioned fault, and is indicated on the map as a dashed line. [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. [42] Marine seismic reflection surveys show it striking northwest across the eastern end of the Strait of Juan de Fuca. [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. But their significance to the Puget Sound area is unknown. An informal consortium of regional agencies has coordinated LIDAR mapping of much of the central Puget Lowland, which has led to discovery of numerous fault scarps which are then investigated by trenching (paleoseismology). [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. I've been in the business for 20 years and the way skilled labor has been treated up until very recently drove a ton of people away from the industry. [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. Document name Date Description Additional versions; 2809: 4/1/2021: . South of the OWL a definite eastern boundary has not been found, with some indications it is indefinite. [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. There are numerous other faults (or fault zones) in the Puget Lowland, and around its edges, sketchily studied and largely unnamed. [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. These mlanges may have been off-shore islands or seamounts that were caught between the Olympic terrane and the North American continent, and were pushed up (obducted) onto the latter. 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). 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. King County Emergency News. Puget Sound and San Juan islands. The first item on your list though is the fault of builders and nobody else. (Not included in QFFDB. Although Washington State's Puget Sound has been shaken every few decades, damage in the region's largest cities, including Seattle, Tacoma and Olympia, has only ever been modest.