southern whidbey island fault map

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. Drop, Cover, and Hold On whenever you feel shaking. The coast is now the home of one of the states largest network of warning sirens called All Hazard Alert Broadcast (AHABs). This photo shows a fence that was offset about 8.5 feet during the 1906 Great San Francisco Earthquake on the San Andreas fault. x\[s8~OU)! Aftershocks can be nearly as large as the main earthquake and can cause significant additional damage. 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. The northwestern part of the fault zone forms the northeastern limit of the Port Townsend basin (Brocher and others, 2001 #4718). During site visits in 2005, Sherrods team found evidence of four SWIF earthquakes in the past 30,000 years. Tsunami waves can travel over 500 miles per hour in the open ocean. Drop to your hands and knees. Most of the populated areas of the state have a 4080% chance of having an earthquake in the next 50 years. 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. Since the last ice age, the southern Whidbey Island fault zone has probably spawned several highly destructive shallow earthquakes. This scenario was modeled on the part of the SWIF from Woodinville to just west of Whidbey Island. A low-angle fault, which is not conclusively earthquake related, separates a diamicton from the overlying recessional outwash deposit. The shaking usually lasts less than a minute and doesnt generally cause a tsunami or have many aftershocks. So they dont necessarily know the threats they face.. Sherrods son has since completed graduate school in applied geosciences. Even if the earthquake is too small to be felt by people, seismographs can detect it. Photo from, This image shows the how the 1700 AD tsunami from the Pacific Northwest crossed the Pacific Ocean. The next earthquake is inevitable, but the variability makes it difficult to know exactly when. Once the shaking has stopped, exit the building if it is safe to do so. Under a scenario played out in a 2019 U.S. Department of Homeland Security study, state-maintained bridges would be severely damaged, leaving them unusable for months or years. An earthquake along the southern Whidbey Island fault reshaped the land some 2,700 years ago. Around Puget Sound, it seems everyone knows about The Big One, the potential magnitude 9.0 Cascadia Subduction Zone megaquake some scientists say is due any day. These maps are created by small planes that use a specific type of laser to measure the elevation of the ground. The last major earthquake was over 300 years ago. " A lot of people are transplants, " Forson said. Washington has the second highest risk in the U.S. of these large and damaging earthquakes because of its geologic setting. ; (5) large-scale liquefaction features in upper Quaternary sediments within the fault zone; and (6) minor historical seismicity. And experts fear it could be even worse than The Big One.. The video is also available in Spanish and there is a fun activity/coloring book that can be found here. 1 School of Earth and Ocean Sciences, University of Victoria, Victoria, British Columbia V8P 5C2, Canada 2 Department of Earth and Environment, Boston University, Boston, Massachusetts 02215, USA That could spell trouble not only for its namesake island but for south and north King County and further west. Stay away from glass, windows, outside doors and walls, and anything that could fall down. Geologic maps of 7.5-minute topographic quadrangles covering parts of the Seattle fault and southern Whidbey Island fault zone are available on the DNR website as: Sign-up for DNR enewsletters. The strength of ground shaking (called strong motion by seismologists) usually decreases with distance from the earthquake source. Shallow faults produce earthquakes in the upper 18 miles (30 kilometers) of the Earths crust. Everything points to one thing, Sherrod said, waving his hand across the inland sea. Read more below to learn about how and where earthquakes occur, what to do before, during, and after an earthquake, and what scientists are doing to learn more about them. A reverse fault occurs when two blocks are pushed together and one moves up and over the other. The term active can have different meanings. In fact, new faults are found every year during our geologic mapping efforts. In the early 2000s, USGS scientists including Brian Sherrod set out to further Johnsons work and better understand the slumbering fissure. Even when the location of a fault is known, there is much additional work to determine how hazardous it may be. Theyre FREE CLICK HERE to subscribe, EAR TO THE GROUND WITH DNR & COMMISSIONER FRANZ, Tree Link helps you answer questions about urbantrees. The tsunami becomes taller as the ocean becomes shallow. 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. Resources on tsunami danger and preparedness in Westport, Grays Harbor County, Long Beach Peninsula, and Coastal evacuation maps. Much of the Southern Whidbey Island fault zone (SWIF), which runs in a north-westward direction from Woodinville to near Port Townsend, Washington, remains mostly . 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. document.getElementById( "ak_js_1" ).setAttribute( "value", ( new Date() ).getTime() ); This site uses Akismet to reduce spam. Strabge sounds very good report thanks a lot. 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. Ground shaking is a hazard near the epicenter of an earthquake and also in areas far from the earthquake where amplification occurs. They didnt grow up here, they havent heard this story. Years ago, Howard Gower and James Yount came to the Puget lowlands to study earthquake risks and stumbled on what appeared to be a fault in Island and Snohomish counties. Though it was not directly related to Johnsons work, he asked a friend working for Mobil Oil to pass along the information. Jump from 60 to 600 per week in just 5 years in Pahala, Is the Cascadia Subduction Zone about to blow? Over time, fault movement has created some interesting geologic features. A normal fault occurs when two blocks are pulled away from each other. Because after a region-wide event, it could take that long for help to come from the rest of the country and world. Unlike sound, ground shaking can be amplified or attenuated (made less) depending on the type of material at the Earths surface. The Seattle Fault is also likely to create a tsunami that would inundate Harbor Island and much of SODO, Interbay, and the waterfront. And what were looking at is water.. Most faults are considered active if they have evidence for movement (this includes earthquakes) within the past 12,000 years (the Holocene time period). A seiche is a large standing wave caused by the resonance of a particular period of wave energy. Johnson and others (1996 #4751) described the structure and stratigraphy of the southern Whidbey Island fault zone. Move away from buildings, streetlights, and utility wires if you can. Small fires are the most common hazard after an earthquake. But opting out of some of these cookies may affect your browsing experience. HAZARD MAPS As part of the Hazard Mitigation Planning process, mapping of the hazards that have the potential to affect the jurisdiction is performed using geographic information systems (GIS) software. Someone screams. The Survey conducts and publishes geologic mapping to identify and characterize faults throughout the state. In fact, until the 1980s, no one knew SWIF existed. View Earthquake Map Faults Interactive fault map and comprehensive geologically based information on known or suspected active faults and folds in the United States. The Seattle fault is a good example of a fault that is mostly reverse. The publication Faults and Earthquakes in Washington State is a state-wide compilation of active faults and folds. The risk is complicated, but there are millions of people who live in the Seattle area, said Forson. Proceed cautiously once the earthquake has stopped. For example, the DNR team found evidence that the rocks creating Snoqualmie Falls are much younger than previously thought. This diagram shows the many types of active faults and the general location of past earthquakes in Washington. You can look at different geological hazard mapson the website of the Department of Natural Resources. This is a hypothetical scenario created by Mark Murphy of the Snohomish County Department of Emergency Management. Beef Barley and French Onion trenches cross the Little Bear Creek lineament. Black lines are trace projections of the South Whidbey Island Fault, Seattle Fault Zone, and Tacoma Fault Zone faults and the N-S Hood Canal and Puget Sound faults of S. Y. Johnson et al. Like a sonogram, the seismic surveys allowed Johnson to see outlines of massive fissures in the earths crust. Faults often occur at and near the boundary of large tectonic plates because the plates are moving in different directions. Notable earthquakes in bold happened in Washington. Each year we map additional areas and learn more about existing faults and (or) discover new ones. Not all faults are active. Landslides can be caused by strong ground shaking during an earthquake. After the shaking stopped the sand regained its strength. What are the most dangerous fault lines for Seattle? Once a fault is located, it is important to know if it is active. Additional fault studies by state and federal geologists in the next few years will help determine the frequency and severity of earthquakes along these fault zones. Although both seiches and tsunamis can be large and destructive, they are created differently. Higher risk areas are in orange and lower risk areas are in green. After the shaking stopped the sand regained its strength. The Seattle Fault is a zone of multiple shallow east-west thrust faults that cross the Puget Sound Lowland and through Seattle (in the U.S. state of Washington) in the vicinity of Interstate Highway 90.The Seattle Fault was first recognized as a significant seismic hazard in 1992, when a set of reports showed that about 1,100 years ago it was the scene of a major earthquake of about . The bluff, where the cabins now sit, could have jutted up in the most recent Whidbey fault quake, Sherrod said. It may not be possible to find water, fuel, or food until services are restored days or even weeks after the event. This kind of landslide is called an earthquake-triggered landslides. 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). The fault's length depends on whom you ask, Sherrod said. And being ready means being able to support yourself, your loved ones, your neighborhood for 2 weeks. Theres a reason the lands around the Pacific Ocean are called the Ring of Fire. The earthquakes, tsunamis, and the proximity of volcanos are all part of the same system. Other faults are inactive and are left over from much older periods of deformation. Swarm of hundreds of small earthquakes rattle Vancouver Island. The April 1949 Tacoma earthquake measured 7.1 on the Richter Scale and caused damage from southern Oregon to British Columbia. A pair of scientists with the U.S. Geological Survey first theorized that a fissure between two major blocks of the earths crust might run through this slice of Puget Sound. By clicking Accept, you consent to the use of ALL the cookies. Each of the earthquakes listed on the bottom of the screen is capable of significant damage. Floods. Photo courtesy of MOHAI (neg. The age of the earthquake is learned by dating the organic material in these tsunami deposits. A lot of people are transplants, Forson said. For several years, scientists pondered where this important regional fault zone continues southwestward from its mapped location in the Everett area. A baristas hand hovers over the bean grinder. <> Were working on pedestrian evacuation maps that show the best routes for pedestrians to take to evacuate, said Forson. East of Puget Sound, the SWIF makes landfall between the cities of Seattle and Everett but is concealed . Geologists have used the location of these shallow, intermediate, and deep earthquakes to learn about subduction zones throughout the world. The Cascadia Subduction Zone (also known as the CSZ) is a 700-mile long fault zone located off the western coastline of British Columbia, Washington, Oregon and northern California. Earthquakes, tornadoes, hurricanes, pandemics, too many people think it cant happen to them and they still think that they can still make a quick run to Walmart to pick up enough to last for 2-3 days and then the govt. Fir trees near the failure are tilted and indicate rotation into the lake (to the left of the photo). In the 1990s, scientists producedan animationthat shows inundation, and people wont have much time to run to higher ground. Discover in this article the most dangerous earthquake zones for Seattle and its area: The Cascadia Subduction Zone, the Seattle Fault and the South Whidbey Island Fault. Contact Us, Whidbey Office Get On The List To Receive Your Daily Dose Of Weird News And Amazing Phenomena. Both of these things can cause equal or greater damage than the actual earthquake. The below map shows that Seattle and its surroundings is constantly being rattled by small earthquakes and tremors. They didnt recognize the significance of what they found. 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. Coupeville, WA 98239, Main Line: While the intensity of this seismic event has now decreased, a big earthquake is overdue in the region. In this sense, the shaking of the ground is the sound of rocks breaking and moving deep within the Earth. A damaging earthquake is inevitable on this fault, but we do not know exactly when it will happen. Because they rupture at such great depth, their seismic energy is distributed over a large area. This kind of grouping gives us information about how common earthquakes might be and how large an area may be affected. Scientists have been trying to understand how often earthquakes happen for over 100 years. During the shaking liquefaction occurred, the sand lost its strength, and the car sunk. Do you live or work near an area that could have liquefaction? The Cascadia subduction zone last ruptured over 300 years ago on January 26, 1700. For example, a building on soft soil will experience more shaking than the same building on bedrock. Information from seismic-reflection profiles, outcrops, boreholes, and potential field surveys is used to interpret the structure and history of the southern Whidbey Island fault in the Puget Lowland of western Washington. At a downtown coffee shop, the mugs begin to chatter. The average time between large earthquakes is about 535 years, but has been as little as 200 years, and more than 1,000 years. Tsunamis triggered by earthquakes usually require at least a M7 event. The Straight Creek fault in the Cascade Range is an example of this kind of fault and has ~5060 miles of movement across it. Its certainly not to scare you. Radiocarbon ages of macrofossils constrain uplift timing to 2.83.2 ka. The evidence shows each lake rests on different free-floating jigsaw pieces of planetary crust, separated by the southern Whidbey Island fault. Hold on to any sturdy shelter until the shaking stops. Others, like the Seattle fault and southern Whidbey Island fault zone, cross under major cities and pose a significant hazard. This means that when the Seattle fault ruptures the south side of the fault moves up relative to the north side. Both types of faults can cause ground shaking during an earthquake and may cause permanent deformation of the ground. Restoring tap water to some homes could take over a year. For some active faults, such as the Seattle fault or Cascadia subduction zone, we can also learn how often large earthquakes have happened in the past. The French Onion trench exposed glaciolacustrine claystones, till, colluvial deposits, and Holocene soils. #4747 Blakely, R.J., Wells, R.E., and Weaver, C.S., 1999, Puget Sound aeromagnetic maps and data: U.S. Geological Survey Open-File Report 99-514. It could also create dangerous currents and hazards to the north including Everett. Buildings could sustain extensive damage. Liquefaction has caused significant damage during earthquakes in Washington. This website uses cookies to improve your experience while you navigate through the website. A few miles southeast across the white-capped waves of Admiralty Bay, Lake Hancock rises and falls with the tides. Theres an uneasy hush. Once in the open, Drop, Cover, and Hold On. Geologists at the Survey spend time mapping the geology of the state, looking for faults, folds, landslides, and different rock types. Southeast Extension of the Southern Whidbey Island Fault By Human Capital March 19, 2019. sw_whidbeyfault_rev122706.pdf (28.68 KB)

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