. Geographic boundaries of Puget Sound and the Salish Sea Fault line puts Seattle at risk of 'The Big One' - UW Magazine [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. The maps show slightly lower . Sail Date . 2-5 Cruises Age 60s. [134] Most authors align it with the strong gravitational anomaly (which typically reflects where faulting has juxtaposed rock of different density) and topographical lineament down Commencement Bay. ISNS 2359 Earthquakes and Volcanoes Chapter 5 Questions - Quizlet 1 earthquake in the past 7 days. The energy of the somewhat smaller Benioff earthquakes is likewise diluted over a relatively large area. [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. Seattle Fault Zone in Central Puget Sound Washington Military Department FEMA Emergency Management Division . [73] The presence of detritus from the Idaho Batholith[72] indicates a former location closer to southern Idaho. WASHINGTON: Methane Bubbles Up From Seafloor Near Seattle News Media at VA Puget Sound health care, 206-764-2435, 206-764-2317. ISNS Ch 5 Flashcards | Quizlet North Olympic Peninsula VA Clinic at VA Puget Sound health care, 360-565-7420. 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. Nor does this uplift delineate any significant basin between it and the Devils Mountain Fault. Those Hollywood depictions of a. See. Slippage along the SWIF would be expected to continue east-southeast until it merged with the OWL, but instead appears to be taking a shortcut ("right step") along the RMFZ. The structure of the Seattle Fault zone still have great uncertainty and there exist a number of interpretations. 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. "Most often, when we think of tsunamis, we think of our outer coast and communities along the Pacific Ocean. ecc.kc@kingcounty.gov. These maps are based on only one Cascadia scenario. 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. Offsets in the eastwest oriented Monroe Fault (south side of the Skykomish River), earthquake focal mechanisms, and kinematic indications show that the CCFZ is a left-lateral strike-slip fault, possibly with some oblique motion (up on the eastern side). Turkey's Fault Line is Similar to Faults Under Puget Sound | KUOW Officials on Tuesday said they believe that more than 7,000 people are dead after a magnitude 7.8 earthquake shook southern Turkey, near the Turkish-Syrian border. [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. [206] This line may also mark the northwestern boundary of the SWCC. 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. [40], The Southern Whidbey Island Fault (SWIF) is a significant terrane boundary manifested as an approximately four mile wide zone of complex transpressional faulting with at least three strands. On the eastern side, where the SWCC is believed to be in contact with pre-Tertiary terranes accreted to the North American craton, matters are different. The first item on your list though is the fault of builders and nobody else. [193] The SHZ and WRZ lie just outside the topographical basin that constitutes the Puget Lowland (see image), do not participate in the uplift and basin pattern, and unlike the rest of the faults in the Puget Lowland (which are reverse or thrust faults reflecting mostly compressive forces) they appear to be strike-slip faults; they reflect a geological context distinctly different from the rest of the Puget Lowland. slope, need not be high. [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. Yet the former is only the first of at least six more parallel southeast striking faults, which do cross the Salzer Creek Fault. This forms a pocket or trough what one local geologist calls the "big hole between the mountains"[17] between the Cascades on the east and the Olympic Mountains and Willapa Hills on the west. One study of seismic vulnerability of bridges in the Seattle Tacoma area[4] estimated that an M 7 earthquake on the Seattle or Tacoma faults would cause nearly as much damage as a M 9 subduction earthquake. 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. 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. The Devils Mountain Fault separates two similar but distinctive ensembles of Mesozoic (pre-Tertiary, before the dinosaurs died) or older rock. 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. 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. While there is a bit of uplifted pre-Tertiary rock between the SPF and UPF, this does not truly fit the uplift and basin pattern described above because of the small scale (2km wide rather than around 20), and because the uplift here is entirely like a wedge being popped out between two nearly vertical faults, rather than being forced over a ramp such as is involved with the Seattle and Tacoma faults. Cluster of earthquakes in Puget Sound considered 'normal', earthquake researchers say. Page 2 of 4 / 2012-2013 Type of Earthquake Most earthquake hazards result from ground shaking caused by seismic waves that radiate out from a fault when it ruptures. 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. [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. Cheney also mapped the Lake Chaplain Fault, parallel and just east of the MVF, from Lake Chaplain to Granite Falls. An earthquake occurs along a south-moving fault. [58], Paleoseismological studies of the SWIF are scant. Puget Sound Energy. [126], An emerging view is that the Dewatto fault marks the western edge of the relatively rigid Seattle Uplift (see map). Clearance, service lines and meter locations. Harold Tobin, . 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). The SWCC appears to be Tertiary marine sediments, not the pre-Tertiary metamorphic rock of the Cascades province; this would seem to make it part of the Coast Range province, with the Coast RangeCascade contact further east. How the CRBF might run north of Seattle (specifically, north of the OWL, which Seattle straddles) is unknown, and even questioned, as there is no direct evidence of such a fault. Methane Plume Emissions Associated With Puget Sound Faults in the Cascadia Forearc. 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. This structure is shown in the gravitational mapping of 1965, but without comment. 1958 and Geologic Map GM-34 for details.). 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]. [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. [82] They estimate the fault is within a few miles of the surface and was active as recently as 1,000 to 1,100 years ago. The Devils Mountain Fault is seismically active, and there is evidence of Holocene offsets. The map also shows potentially active faults from a separate 2014 report (click here to download). Does the public have a right to walk across a - Puget Sound Institute [181] What is unknown is whether this was due to a great subduction earthquake, to the noted earthquake on the Seattle Fault about that time, or to an earthquake on a local fault (e.g., the Olympia structure); there is some evidence that there were two earthquakes over a short time period. Nurse Recruiter at VA Puget Sound health care, 206-764-2487. 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. [185] The prospect of a major earthquake on the Doty Fault poses a serious hazard to the entire Puget Sound region as it threatens vital economic lifelines: At Chehalis there is but a single freeway (Interstate 5) and a single rail line connecting the Puget Sound region with the rest of the west coast; the only alternate routes are very lengthy.[186]. The Puget Sound faults under the highly populated Seattle and Puget Sound region of Washington state form a regional network of interrelated seismologic geologic faults. Five Puget Sound cities likely to feel strong shaking in a megaquake There are numerous other faults (or fault zones) in the Puget Lowland, and around its edges, sketchily studied and largely unnamed. Harold Tobin, a researcher at the University of Washington and director of the Pacific Northwest Seismic Network, says the fault line that caused earthquake that shook southern Turkey near the Turkish-Syrian border and killed more than 7,000 people is similar to the faults under Puget Sound. The Seattle Fault crosses east-west through Puget Sound and downtown Seattle. Analyze Instructions: Close. Several possible explanations of the enhanced conductivity have been considered; Eocene marine sediments containing brine are most likely (. 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. Subsidence dated to between AD 1445 and 1655 has been reported in Mud Bay (just west of Olympia). Glacially deposited and shaped fill covers most of the lower elevations of Puget Sound. A marine seismic reflection study[177] found evidence of faulting at the mouth of Budd Inlet, just north of the Olympia structure, and aligning with faint lineaments seen in the lidar imagery. 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. [98] This turns and runs just south of Victoria, nearly in-line with the SWIF. The principal effects of this complex interplay of forces on the near-surface crust underlying the Puget Lowland are: Further complicating this is a feature of unknown structure and origin, the OlympicWallowa Lineament (OWL). The EPZ is active, being the locale of the 1995 M 5 Point Robinson earthquake.[136]. Tobin says offshore faults tend to cause bigger earthquakes and are a larger tsunami risk. KUOW Public Radio on Twitter: "A UW researcher says the fault line that Earthquakes occur nearly every day in Washington. See Snavely et al. It has been suggested that a corresponding change in the character of the SWIF may reflect a change in the direction of regional crustal strain. 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. Tsunami waves as high as 42 feet could crash into Seattle within The Puget Sound region is not just potentially seismic, it is actively seismic. Methane Plume Emissions Associated With Puget Sound Faults in the [102] Or the Crescent margin may simply (and quietly) just run south-southeast under Seattle to the WRZ. Aeromagnetic surveys,[13] seismic tomography,[14] and other studies have also contributed to locating and understanding these faults. . After all, Olympia, which is the closest of the cities to the megathrust fault, is estimated to experience the least severe shaking; at the same time, many cities on the east side of the Puget Sound further away from the fault experience much stronger shaking. Piecing together the puzzle of the Seattle Fault Zone Movement on the southern segment of the DDMFZ that converges with the SCF the Darrington Fault was, as on the SCF itself, right-lateral. [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.