The continued movement along faults over millions of years can build mountains, tear a continent apart, and move tectonic plates thousands of miles. Hundreds could die, with thousands more injured. Most are too small to be felt or cause damage. In Seattle, the quake damaged buildings, weakened bridges, started fires and opened cracks in the earth. The southern Whidbey Island fault, and several others, were exposed for the first time from a camouflage of forest, ocean and glacial sediment. Other faults are inactive and are left over from much older periods of deformation. Its significantly larger than the Seattle Fault, and South Whidbey could hand us a magnitude 7.5 earthquake. Sensitive seismographs located throughout the state, and all over the world, measure this seismic energy. Learn how your comment data is processed. The Survey is working with the Office of the Superintendent of Public Instruction (OSPI) and Reid Middleton, an engineering firm, to perform seismic safety assessments of 220 school buildings across the state. Buildings could sustain extensive damage. The risk is complicated, but there are millions of people who live in the Seattle area, said Forson. Theres an uneasy hush. Graphic from IRIS. The Cascadia subduction zone along the Washington and Oregon coast is one of the biggest hazards to our state and is a good examples of this kind of fault. This part of the Japanese coast had not seen this type of seismic rupture in some 800 years, and what failed was that walls built to keep tsunami waves were not high enough. 12201 Sunrise Valley Drive Reston, VA 20192, Region 2: South Atlantic-Gulf (Includes Puerto Rico and the U.S. Virgin Islands), Region 12: Pacific Islands (American Samoa, Hawaii, Guam, Commonwealth of the Northern Mariana Islands), The southern Whidbey Island fault: An active structure in the Puget Lowland, Washington, S. Y. Johnson, C. J. Potter, J.M. This means that when the Seattle fault ruptures the south side of the fault moves up relative to the north side. This fault produces some of the largest and most damaging earthquakes in the world (M9). EVERETT The South Whidbey Island Fault is connected to a system of powerful earthquake fault lines stretching from Victoria, B.C., to Yakima that is capable of unleashing a devastating. M 7.4 Scenario Earthquake - Southern Whidbey Island fault-southern Overview Interactive Map Regional Information Impact ShakeMap Technical Origin Download Event KML Earthquakes Hazards Data & Products Learn Monitoring Research M 7.4 Scenario Earthquake - Southern Whidbey Island fault-southern 2017-05-12 20:14:09 (UTC) 48.036N 122.452W Some residents may lose housing temporarily or permanently. The map is from a 2007 report (click here to download) on seismic design categories in Washington. %
One model suggests it extends to about 30 miles east of Yakima. Even when an earthquake happens on a fault that doesnt reach the surface, the ground can still show signs of cracking. Everything points to one thing, Sherrod said, waving his hand across the inland sea. Snohomish, King and Island counties would be expected to see the. This northwest-trending fault comprises a broad (as wide as 6-11 km), steep, northeast-dipping zone that includes several splays with inferred strike-slip, reverse, and thrust displacement. In the 1990s, scientists producedan animationthat shows inundation, and people wont have much time to run to higher ground. Along the water at Cama Beach State Park, cabins on a bluff overlook Saratoga Passage, facing the general direction of Lake Hancock on Whidbey Island. This is a hypothetical scenario created by Mark Murphy of the Snohomish County Department of Emergency Management. For earthquakes that occurred before seismographs were invented, the Mercalli Intensity scale was used to make maps of damage and determine the size and location of an earthquake. Johnsons curiosity changed the course of his career. Larger crustal faults, such as the Seattle fault and southern Whidbey Island fault zone, can produce earthquakes up to magnitude 7.5. These include the: Southern Whidbey Island Fault (SWIF) Seattle Fault Devils Mountain Fault Strawberry Point fault Utsalady Point fault Know what to expect. In this photo, visitors to Green Lake Park near Seattle, Washington, have parked their bicycles as they look at the cracks made by the April 1949 earthquake. Since their initial discovery, research has shown that the actual number of earthquakes is somewhere between 5 and 10 for each change in magnitude. The southern Whidbey fault is shallow, running right under Snohomish County as opposed to many miles off shore like the Cascadia fault. DO NOT get in a doorway. Each year we map additional areas and learn more about existing faults and (or) discover new ones. The team determined that the Rattlesnake Mountain fault zone, originally mapped by DNR geologist Tim Walsh in the 1980s, is likely the southern continuation of the southern Whidbey Island fault, extending this fault zone from the Strait of Juan de Fuca to Rattlesnake Mountain near North Bend. The fault has at least three almost parallel strands within a 4- to 7-mile-wide band, stretching eastward from Vancouver Island. Coupeville, WA 98239, Main Line:
Earthquakes can trigger landslides and tsunamis which can happen after the main event. South Whidbey Island Fault (SWIF) M7.4 Earthquake Scenario Fire (Vegetation Condition Class) . The Seattle Fault is also likely to create a tsunami that would inundate Harbor Island and much of SODO, Interbay, and the waterfront. Clicking on the map will download the publication. Stories from tribes near Seattle have also helped us to learn that the last earthquake on the Seattle fault was about AD 900950. The Cascade block to the northeast is floored by diverse assemblages of pre-Tertiary rocks; the Coast Range block to the southwest is floored by lower Eocene marine basaltic rocks of the Crescent Formation. Within this rich oral history there are many references to events like earthquakes and tsunamis. , * NOTE: Hazard maps for each jurisdiction will only be included if that jurisdiction is at risk to that hazard., Copyright Island County. What scientists dont know is its timing interval. It will happen; we dont know when.. The last major earthquake was over 300 years ago. High-resolution LiDAR topographic maps have since revealed several potential faults scarps, and subsequent studies provide more detailed information about the fault zone's past. This northwest-trending fault zone extends more than 65 km across Possession Sound, southern Whidbey Island, Admiralty Inlet into the eastern Strait of Juan de Fuca. Additionally, because the continent moves up and over the ocean plate, large amounts of sea water are displaced and cause damaging tsunamis. The 1964 M9.2 Alaska earthquake created a large tsunami from the fault rupture, and many smaller tsunamis from on-land and underwater landslides. Because Japan was so well prepared, mostretrofitted buildingsoutside of the tsunami zone survived. But Forson says you also need to know what to do when the shaking happens. Earthquakes. The shaking usually lasts less than a minute and doesnt generally cause a tsunami or have many aftershocks. The experts say few are ready. A baristas hand hovers over the bean grinder. The most important thing you can do before the next earthquake is to prepare. Volcanic eruptions. You also have the option to opt-out of these cookies. Other types of seismic energy (S waves) also travel through the earth, but they move with a side-to-side (shearing) motion. Large and damaging earthquakes are inevitable in Washington, but no one knows exactly when they will happen. The largest active fault that will affect Washington (and the whole Pacific Northwest) is the Cascadia subduction zone. The faults length depends on whom you ask, Sherrod said. The northwestern part of the fault zone forms the northeastern limit of the Port Townsend basin (Brocher and others, 2001 #4718). Sherrod says practically every place they. Even when the location of a fault is known, there is much additional work to determine how hazardous it may be. But opting out of some of these cookies may affect your browsing experience. On a frigid, blustery day in December 2018, Sherrod revisited the site where he conducted much of his field work. By finding the age of the deformed layer, a paleoseismologist can determine the minimum age of the fault. Out of these, the cookies that are categorized as necessary are stored on your browser as they are essential for the working of basic functionalities of the website. These fault strands follow the valley edges and control the location of the Snoqualmie River along some portions of the valley. The crustal faults the Seattle Fault, the South Whidbey Island Fault, the Tacoma Fault those are less well known, said Forson. and the Red Cross will be there to care for them. Gower (1980 #6229) showed and named the "southern Whidbey Island fault," and Gower and others (1985 #4725) showed this fault on their seismotectonic map of the Puget Sound region and briefly outlined its geologic relationships. After large earthquakes there are usually many aftershock earthquakes. Jump from 60 to 600 per week in just 5 years in Pahala, Is the Cascadia Subduction Zone about to blow? Because they can travel great distances, tsunamis generated from earthquakes across the ocean can still cause damage. Since about 1870 there have been about 15 large earthquakes (greater than M5) in the state. Stay inside until the shaking stops and it is safe to go outside. Experts have warned that UK outbreak may be around two weeks behind Italys. Electricity, water, natural gas, and phones may not work. So they dont necessarily know the threats they face.. One of the best views of SWIF should be from Grand Avenue Park in Everett. Customers lift their eyes from phone screens. Brick chimneys cascade off rooftops. But they didnt document it hardly at all.. For example, a building on soft soil will experience more shaking than the same building on bedrock. We work closely with the Washington Emergency Management Division, the Washington Seismic Safety Committee, and the Federal Emergency Management Agency to ensure that the best-available science is used in the development of hazard mitigation plans. The Survey has developed several types of hazard maps for different types of earthquake- and fault-related hazards: The maps are used by state and local governments to develop and update hazard-mitigation and response plans, and to mark geologically hazardous areas. As of January 12, 2017, the USGS maintains a limited number of metadata fields that characterize the Quaternary faults and folds of the United States. The southern Whidbey Island fault zone (SWIF), as previously mapped using borehole data, potential field anomalies, and marine seismic reflection surveys, consists of three subparallel, northwest trending strands extending ~100 km from near Vancouver Island to the northern Puget Lowland. 1 NE 7th Street
Sherrod and others, 2008 #7652) report results from four trenches located near Crystal Lake: Flying Squirrel trench (572-5), Mountain Beaver trench (572-6), Beef Barley trench (572-7), and French Onion trench (572-8). In some areas getting up a hill to higher ground will be difficult. The years have gone by. But it didnt. During site visits in 2005, Sherrods team found evidence of four SWIF earthquakes in the past 30,000 years. In Washington, we do not have tsunami walls. Subtle scarps and topographic lineaments on Pleistocene surfaces are visible on high-resolution LiDAR topography at a number of locations (Sherrod and others, 2008 #7652); the northeast-side-up scarps exhibit 15 m of vertical relief, late glacial and post-glacial sediments (Sherrod and others, 2008 #7652). The height difference likely was caused by a 7.5 magnitude earthquake on the fault about 2,700 years ago, Sherrod said. Source: United States Geological Survey. So the fault remained mostly a mystery until the 1990s. This video from the 2011 Tohoku subduction zone earthquake shows the earthquakes before, during, and after the main M8.7 event on March 11 (at 1:50 in the video). However, we can learn which faults are active and which are inactive. Bending of the fault and transpressional deformation began during the late middle Eocene and continues to the present. Story telling is an important part of the Native tradition and is how their history is passed down to the next generation. That place is the Ocosta School. The last large earthquake on the Cascadia subduction zone was in 1700. That could spell trouble not only for its namesake island but for south and north King County and further west. While the intensity of this seismic event has now decreased, a big earthquake is overdue in the region. You will not be able to google what to do in an earthquake when it is happening. Walsh said that Whidbey Island through the years has been subjected to a number of small quakes, roughly 2 or 3 on the Richter scale. In much of Washington, dense vegetation covers the land and makes finding faults very difficult. Charles Richter and Beno Gutenberg discovered that for every magnitude of earthquake, there are about ten times more earthquakes of the next lower magnitude. At the Brightwater treatment plant in Woodinville and at Crystal Lake in Maltby, the government researchers found telltale slopes of offset ground, known as scarps, indicative of a long-ago quake. A lock () or https:// means youve safely connected to the .gov website. The northwest-trending southern Whidbey Island fault zone occurs along a significant terrane boundary between basement blocks underlain by Eocene marine basalts of the Coast Range province to the southwest and pre-Tertiary metamorphic rocks of the Cascades province to the northeast. The tsunamis can travel far inland and deposit layers of sand and organic material. The Cascadia subduction zone off the Washington and Oregon coast is capable of some of the largest earthquakes in the world. You have entered an incorrect email address! Also, very large earthquakes were difficult to measure accurately. The southern Whidbey fault is unlike more visible faults on the West Coast. Hey Biden! Experts believe a magnitude 9.0 could happen there anytime in the next 200 years or so. Maps. Do you know what to do if there is an earthquake? One model suggests it extends to about 30 miles east of Yakima. Each peak of the Olympics stuck out with picturesque clarity in the distance. document.getElementById( "ak_js_1" ).setAttribute( "value", ( new Date() ).getTime() ); This site uses Akismet to reduce spam. Expect and help to extinguish fires. Standing becomes almost impossible as the jolts turn to rolling waves. An increase of 2 means that ~1,000 times more energy is released. An official website of the United States government. We do know that it is active and will likely produce a large M67.5 earthquake when it next ruptures. Each of these aftershocks would be a significant earthquake if it happened on its own. Using the stratigraphic column from the Freeport quadrangle map, confirm that you can recognize . Earthquakes between 45 and 185 miles deep are called intermediate, and earthquakes over 185 miles deep are called deep. The trench did expose faults, but it was not possible to conclusively demonstrate offset of Holocene units. Photo from https://buildingfailures.files.wordpress.com/2014/02/tiltedbuilding.jpg. The fault zone is up to 57 km, correlates with gravity and magnetic anomalies (Finn and others, 1991 #4753; Blakely and others, 1999 #4747), and has been interpreted as a complex zone of transpressional deformation (Johnson and others, 1996 #4751). @\;L;=}%FC*l $@ 4x: 888O~xrsxx'/*rGRF\gI%~x(G-^-hjjq
kx/V ou0hyegy0;ei`Tx&ilZ )TmZ$vb,`bQm|DR5x/ The combination of all of these effects is what makes earthquakes such a powerful geologic hazard. A .gov website belongs to an official government organization in the United States. For example, a M7 earthquake releases 32 times more energy than a M6 earthquake, and 1,000 times more than a M5 earthquake. However, seismic tomography studies (Brocher and others, 2001 #4718) reveal that only the northwestern end of the fault zone in the southeastern Strait of Juan de Fuca is associated with a strong velocity contrast. Most injuries occur when people inside change rooms or try to leave the building. A half dozen people reaching for the last can of soup, someone could lose their life over that. Wagner and Wiley (1983 #6230) and Wagner and Tomson (1987 #6249) mapped and briefly discussed offshore parts of this fault zone and also used the name "southern Whidbey Island fault." The below map shows that Seattle and its surroundings is constantly being rattled by small earthquakes and tremors. Unlike sound, ground shaking can be amplified or attenuated (made less) depending on the type of material at the Earths surface. This photo shows a fence that was offset about 8.5 feet during the 1906 Great San Francisco Earthquake on the San Andreas fault. Restoring tap water to some homes could take over a year. Both types of faults can cause ground shaking during an earthquake and may cause permanent deformation of the ground. What we know about this fault is that its ruptured may times in the pastit will happen again. Earthquakes on faults like these may cause tsunamis in the Puget Sound region. A damaging earthquake is inevitable on this fault, but we do not know exactly when it will happen. What are the most dangerous fault lines for Seattle? In the month after the main earthquake there were about 60 M7 and M6 earthquakes. Please visit our Geologic Information Portal and Geologic Hazard Maps page for the most up-to-date listing of all of our hazard maps. The Seattle fault is a good example of a fault that is mostly reverse. The Pacific Tsunami Warning Center is located in Hawaii and is responsible for issuing alerts to all the countries that border the Pacific Ocean. The age of the earthquake is learned by dating the organic material in these tsunami deposits. Photo by Steve Palmer. Geoscientist Brian Sherrod stands near the submerged southern Whidbey Island fault line at the Brightwater Treatment Plant in Woodinville. from Whidbey Island to Vancouver Island (Figure 1). They conclude the observed features have a glaciotectonic origin and are not seimotectonic. People stagger into the streets to avoid an avalanche of debris. The study of seismic waves is called seismology and has allowed scientists to learn much about the internal structure of the Earth.
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