Proceed cautiously once the earthquake has stopped. Image from the Pacific Geoscience Center of the Natural Resources of Canada. Small fires are the most common hazard after an earthquake. For each increase in earthquake magnitude, there are about 10 times fewer earthquakes. Floods. Consider subscribing to our blog, Washington State Geology News, to receive notifications when new information is published. Strait of Juan de Fuca Fault Map 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. One model suggests it extends to about 30 miles east of Yakima. Mapping along the Snoqualmie River valley also helped answer the important question of where the Seattle fault lies east of its last mapped position near Issaquah. 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. A national credit rating service has improved its opinion of WhidbeyHealths financial future. The fault has at least three almost parallel strands within a 4- to 7-mile-wide band, stretching eastward from Vancouver Island. If you are already planning your Christmas gifts, please buy with us on Amazon. The last earthquake on the Seattle fault (about AD 950) triggered a landslide and seiche in Lake Washington. Washington has few large normal faults because it is mostly in a region of compression. Watch the video below to learn how you can be ready for the next earthquake. This date was confirmed by records in Japan of an orphan tsunami and by many lines of geologic evidence. Tsunamis and seiches are destructive waves which can be triggered by certain types of large earthquakes. 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. Moving inland, the Seattle Fault is capable of a magnitude 7. A community meeting about a shelter at the Harbor Inn may have yielded more questions than answers. This movement happens because stress builds up as tectonic plates move. 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. The Westport area is now the first in North America to have acommunity vertical evacuation structure, a building strong enough to resist earthquake and tsunami wave forces and give people a platform above the expected wave heights. Expect aftershocks. @\;L;=}%FC*l $@ 4x: 888O~xrsxx'/*rGRF\gI%~x(G-^-hjjq kx/V ou0hyegy0;ei`Tx&ilZ )TmZ$vb,`bQm|DR5x/ Brick chimneys cascade off rooftops. A strike-slip fault occurs when two blocks move past each other. These quakes are capable of magnitudes from 7 to over 9. We use cookies on our website to give you the most relevant experience by remembering your preferences and repeat visits. PI22343). Tohoku killed nearly 16,000 people; most died as a result of drowning or being crushed in the tsunami. /L\Axc4Q/w4Ks^#, sRITgZf>,e}iI5,F_ADGc?f e@L. Another piece can be seen under the elevated lanes of northbound Interstate 5 in South Seattle not far from the Rainier brewery. The Survey conducts and publishes geologic mapping to identify and characterize faults throughout the state. You will not be able to google what to do in an earthquake when it is happening. This diagram shows the many types of active faults and the general location of past earthquakes in Washington. The boundary between the two plates covers a large area and can lock together. The affiliate sales will help us to continue the hard work we are putting in this website. But quiet period wont last, Strongest earthquake in 40 years rattle residents of Buffalo, NY, Is Istanbul next? Because they rupture at such great depth, their seismic energy is distributed over a large area. In the month after the main earthquake there were about 60 M7 and M6 earthquakes. Map Releases; Topographic (Topo) Maps; Volcanic Maps; All Maps; Multimedia Gallery. If folding on the Little Bear Creek lineament resulted in one or two of unconformities, the poorly constrained timing of the earthquakes is younger than 12,000 yr BP and older than about 2,850 cal yr BP. If a large earthquake happens, be prepared for many more earthquakes. The 1949 earthquake near Tacoma triggered a landslide near the Tacoma Narrows that caused a local tsunami. Image from the, Aquatic Lands Habitat Restoration Program, South Lake Washington Restoration Project, Scientific and Technical Support to Aquatic Programs, Washington Geologic Survey Publications Catalog, Washington Geologic Survey Photograph Collection, Wetlands of High Conservation Value Map Viewer, Timber Sale Remaining Volume by Purchaser Reports, Spanish - Brocha, Salal y Otros Productos Forestales, Complete: Baker to Bellingham Non-Motorized Recreation Plan, Community Wildfire Resilience and Preparedness, Utility Wildland Fire Prevention Advisory Committee, Blanchard, Reiter, Walker Valley and Nearby Islands, Teanaway Community Forest Advisory Committee, Teanaway Community Forest Advisory Committee Past Meetings, Faults and Earthquakes in Washington State, Pacific Northwest Seismic Network Seismo Blog, https://buildingfailures.files.wordpress.com/2014/02/tiltedbuilding.jpg, Pacific Geoscience Center of the Natural Resources of Canada. Each of these aftershocks would be a significant earthquake if it happened on its own. Story telling is an important part of the Native tradition and is how their history is passed down to the next generation. Some events appear to be only 200 years apart, and others are more than 1,000. Experts believe a magnitude 9.0 could happen there anytime in the next 200 years or so. Latest earthquakes map and list (past 24 hours, M2.5+) from the ANSS (Advanced National Seismic System). PO Box 5000 The southern Whidbey fault is unlike more visible faults on the West Coast. Sherrods son has since completed graduate school in applied geosciences. Landslides can be caused by strong ground shaking during an earthquake. A paleoseismologist will look for surface ruptures along faults and may use carbon-14 dating to learn when the rupture happened. District Court: (800) 946-9765, South Whidbey Island Fault (SWIF) M7.4 Earthquake Scenario. 572 Last Review Date: 2016-11-29 A team headed by Joe Dragovich of DNRs Division of Geology and Earth Resources,assisted by geologists from King County, Pacific Northwest Seismic Network, Colorado College, and Washington State University, has been mapping in this area for the past three years. Because after a region-wide event, it could take that long for help to come from the rest of the country and world. The key, Sherrods group would discover, was buried on Whidbey Island under layers of mud, peat moss and decaying marsh grass in the murky tidal waters at Crockett Lake, alongside the Coupeville ferry dock. Tsunamis and seiches can also be triggered by large slides, both on land and underwater. Please visit our Geologic Information Portal and Geologic Hazard Maps page for the most up-to-date listing of all of our hazard maps. 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 A low-angle fault, which is not conclusively earthquake related, separates a diamicton from the overlying recessional outwash deposit. 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. This movement created a tsunami in Puget Sound and triggered a large landslide into Lake Washington. The fault's length depends on whom you ask, Sherrod said. Earthquakes can be measured in many ways, but the most accepted method is called moment magnitude. This was a problem because no two locations would agree on the size of the same earthquake. Although both seiches and tsunamis can be large and destructive, they are created differently. In places where there is little vegetation, different rock types and faults can be found with relative ease. This fault produces some of the largest and most damaging earthquakes in the world (M9). The bluff, where the cabins now sit, could have jutted up in the most recent Whidbey fault quake, Sherrod said. The buildings sank when ground shaking weakened the underlying sediments. A lock () or https:// means youve safely connected to the .gov website. These fault strands follow the valley edges and control the location of the Snoqualmie River along some portions of the valley. Some of these faults are in remote areas. But they didnt document it hardly at all.. The Geologic Information Portal has a Natural Hazards theme that shows active faults and earthquakes. Since the last ice age, the southern Whidbey Island fault zone has probably spawned several highly destructive shallow earthquakes. People are already fighting over toilet paper, just imagine what will it be like when they go shopping for food and the shelves are almost empty. These aftershocks can last for hours to weeks or months. In fact, until the 1980s, no one knew SWIF existed. What are the most dangerous fault lines for Seattle? HOLOCENE FAULT SCARPS AND SHALLOW MAGNETIC ANOMALIES ALONG THE SOUTHERN WHIDBEY ISLAND FAULT ZONE NEAR WOODINVILLE, WASHINGTON By Brian L. Sherrod1, Richard J. Blakely2, Craig Weaver1, Harvey Kelsey3, Elizabeth Barnett1, and Ray Wells4 1 U.S. Geological Survey, Dept. Sometimes Geologists can use the offset land surface to understand how much the fault moved during the earthquake. Scientists have also dated large underwater landslides and turbidites that travel from the continental edge far out into the ocean basin. The southeastern and central parts of the southern Whidbey Island fault zone form the southwest margin of the Everett basin and northeast boundary of the Seattle basin. 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. For example, if there is one M7 earthquakes in an area every 1,000 years, then there will be about 10 M6 earthquakes, 100 M5 earthquakes, and 1,000 M4 earthquakes during the same 1,000 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. In the Puget Sound region, it takes a trained eye to recognize rocky outcrops and subtly raised ground as evidence of a fault. Tsunami waves can travel over 500 miles per hour in the open ocean. 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. Its significantly larger than the Seattle Fault, and South Whidbey could hand us a magnitude 7.5 earthquake. The coast is now the home of one of the states largest network of warning sirens called All Hazard Alert Broadcast (AHABs). 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). Once the shaking has stopped, exit the building if it is safe to do so. What scientists dont know is its timing interval. Sherrod remembers his son, age 5 at the time, playing with toy trucks on the mossy banks of the marsh while the scientists worked. The age of the earthquake is learned by dating the organic material in these tsunami deposits. Faults can be grouped based on their relative movement into three types. Even places that are far from active faults are still at risk during a large Cascadia subduction zone earthquake. The years have gone by. Identify and secure items in your home or work that could cause damage. What makes these faults mega is that the amount of energy released is hundreds to thousands of times more than almost any other type of fault. Stratigraphy in the Flying Squirrel trench showed gentle warping of late glacial and post-glacial sediments; no faults were exposed. Most faults are considered active if they have evidence for movement (this includes earthquakes) within the past 12,000 years (the Holocene time period). Everything points to one thing, Sherrod said, waving his hand across the inland sea. The Seattle fault last ruptured about 1,100 years ago in AD 900950. Black squares are urban sewer outfalls, which don't match the bubble plumes' locations. Most faults in Washington are a mix of a strike-slip fault and a thrust or reverse fault. The study of seismic waves is called seismology and has allowed scientists to learn much about the internal structure of the Earth. Whats up with the 50 US nuclear bombs stored at the Incirlik Air Base in Turkey, right on the same fault line California hasnt seen a catastrophic earthquake recently. It devastated the coast of the Pacific Northwest and sent an orphan tsunami to Japan. 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. The southern Whidbey Island fault divides the two. It is a qualitative scale that ranges from IXI (1-11) and measures the amount of damage caused by an event. Faults are features in the Earths crust where rock periodically breaks and moves, releasing seismic energy and creating an earthquake. Standing becomes almost impossible as the jolts turn to rolling waves. It forms the northern boundary of the Everett basin and lies along a series of high-amplitude aeromagnetic anomalies that extend from the Cascade Mountains to Vancouver Island, B.C. The southern Whidbey Island fault: An active structure in the Puget Lowland Washington, Geological Society of America Bulletin 1996;108;334-354. , * NOTE: Hazard maps for each jurisdiction will only be included if that jurisdiction is at risk to that hazard., Copyright Island County. Coupeville, WA 98239, Main Line: Since about 1870 there have been about 15 large earthquakes (greater than M5) in the state. On a brilliant November day, Sherrod took in the panorama from the parks bluff. Notice the Seattle Fault Zone bounding the Seattle Basin to the south. Learning earthquake faults around where we live is a first good way to prepare the next devastating earthquake. In this sense, the shaking of the ground is the sound of rocks breaking and moving deep within the Earth. In Washington, we do not have tsunami walls. Even when the location of a fault is known, there is much additional work to determine how hazardous it may be. Necessary cookies are absolutely essential for the website to function properly. endobj The most important thing you can do before the next earthquake is to prepare. South Whidbey Island Fault Zone. Early mapping of the three subparallel, northwest trending strands of the southern Whidbey Island fault zone was constrained by borehole data, potential field anomalies, marine seismic reflection surveys. They havent dug up enough history to estimate. 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 . One of the best views of SWIF should be from Grand Avenue Park in Everett. It might as well have been sitting in a drawer, Johnson said. Stop as quickly as safety permits and stay in the vehicle. This is a very good example of a strike-slip fault. The buildings sank when ground shaking weakened the underlying sediments. Most are too small to be felt or cause damage. Charles Richter and Beno Gutenberg discovered that for every magnitude of earthquake, there are about ten times more earthquakes of the next lower magnitude. 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. Disoriented drivers wonder whats wrong with their cars, then realize something much bigger is amiss. Some residents may lose housing temporarily or permanently. Save my name, email, and website in this browser for the next time I comment. Official websites use .gov Mudslides. For example, a building on soft soil will experience more shaking than the same building on bedrock. Because Japan was so well prepared, mostretrofitted buildingsoutside of the tsunami zone survived. Move away from buildings, streetlights, and utility wires if you can. 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. Some types of seismic energy (P waves) are similar to sound energy that is released if you break a twig or slide a chair across the floor. Thats why were pushing for a lot of vertical evacuation structures to be built hotels or schools, because its not an easy problem to solve, he said. The Flying Squirrel and Mountain Beaver trenches cross the Cottage Lake lineament. Stay away from glass, windows, outside doors and walls, and anything that could fall down. The western half of Washington state is considered earthquake country, with the potential for very large quakes. This is similar to how sound is quieter when you move away from a speaker. This means that a large area feels the shaking, but the intensity is less than a similar shallow earthquake. These faults and earthquakes usually occur at great depth (tens to hundreds of miles). His team wanted to find the rate of sea level rise along the shore. They conclude the observed features have a glaciotectonic origin and are not seimotectonic. Never use a lighter or match near damaged areas. So the fault remained mostly a mystery until the 1990s. Seismic waves travel at hundreds to thousands of miles per hour and quickly reach the surface where they are felt or measured. In general, larger faults make larger earthquakes. There are also many faults that have not been studied enough to know if they are active. Higher risk areas are in orange and lower risk areas are in green. In 1985, with little concrete evidence of its existence, the pair included the possible fault on a geologic map published by the USGS. These maps are created by small planes that use a specific type of laser to measure the elevation of the ground. 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). America is going to be punished just like the rest of the world. The publication Faults and Earthquakes in Washington State is a state-wide compilation of active faults and folds. Cover your head and neck with your arms to protect against falling debris. When earthquakes occur on faults that reach the Earths surface, the ground may rupture. Johnson, on a whim, acquired the data that would prove its existence beyond a doubt. Theres an uneasy hush. They didnt grow up here, they havent heard this story. 2 0 obj An earthquake can be a scary event. Check out the liquefaction susceptibility and NEHRP site class maps on the Geologic Hazard Maps page. This car was parked on sand during the 2011 earthquake in Christchurch, New Zealand. <> When this happens, even a very small slope can cause the ground to slide. The northwestern part of the fault zone forms the northeastern limit of the Port Townsend basin (Brocher and others, 2001 #4718). The average time between large earthquakes is about 535 years, but has been as little as 200 years, and more than 1,000 years. A reverse fault occurs when two blocks are pushed together and one moves up and over the other. The Darrington-Devils Mountain fault zone is located in southern Skagit County and northern Snohomish County. Once we got it, we were sort of shocked to see these big faults in the Puget lowlands, he said. Earthquakes can trigger landslides and tsunamis which can happen after the main event. Even when an earthquake happens on a fault that doesnt reach the surface, the ground can still show signs of cracking. The fault, not so much. 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. So I think it is worth your time to learn more about the biggest seismic riskss and major fault lines criss-crossing this part of the Pacific Northwest, namely: Now lets visit the 3 most dangerous earthquake faults for Seattle one by one: The Cascadia Subduction Zone is a giant fault running from Cape Mendocino, Calif. past Oregon and Washington and doesnt end until its north of Vancouver Island in Canada. 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 stream Washington has dozens of active faults and fault zones. Most of the populated areas of the state have a 4080% chance of having an earthquake in the next 50 years. 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. In addition, the Survey performs seismic safety evaluations of schools. Large earthquakes, like those from the Cascadia subduction zone on January 26, 1700, often create tsunamis. Excavations across several LiDAR scarps show evidence for multiple post-glacial folding and faulting event on faults with reverse oblique sense of slip. A special type of shallow fault, called a subduction zone or megathrust, occurs where an oceanic plate moves beneath a continental plate. Each year we map additional areas and learn more about existing faults and (or) discover new ones. SWIF ranges from 12 miles underground at its deepest to right at sea level in a few scattered spots, like Cama Beach, Holmes Harbor and Woodinville, according to Sherrods research. Over time, fault movement has created some interesting geologic features. The process of breaking and moving rock releases a large amount of energy that travels through the Earth as seismic waves. Johnson et al. Then consider that the Seattle Fault is a complex of faults with various branches that run at or just below the surface. But the Cascadia Subduction Zone isnt just a fault; its an overlapping joint between tectonic plates, parts of the Earths crust that float on layers of molten rock. The medic said colleagues were becoming sick and emotionally overwhelmed In Washington, the risk from earthquake-induced landslides is large. These cookies do not store any personal information. Resources on tsunami danger and preparedness in Westport, Grays Harbor County, Long Beach Peninsula, and Coastal evacuation maps. During site visits in 2005, Sherrods team found evidence of four SWIF earthquakes in the past 30,000 years. The South Whidbey Island Fault is also dangerous. Click the "Seismogenic Features" button in the Map Contents window to display faults and earthquakes. Map by And while scientists keep digging for more information and more situational awareness of what we face, the other problem is human. The Southern Whidbay Island Fault represents another major earthquake threat for Seattle and its residents. Hover over a cluster of earthquakes to learn about the different types in the Pacific Northwest. Photo courtesy of MOHAI (neg. Like other faults, when enough stress builds up, the megathrust will rupture. %PDF-1.5 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 zone, known to geologists as SWIF, cuts through Puget Sound in a diagonal line roughly from Port Townsend to the southern tip of Whidbey Island, then to Mukilteo, Bothell, North Bend and possibly farther east below the Cascades. When the landslide hit the water it may have created a tsunami. This map shows areas of seismic risk from high (red) to low (grayish-green). HomePrograms and ServicesGeologyGeologic Hazards. The combination of all of these effects is what makes earthquakes such a powerful geologic hazard. View of the Sunset Lake liquefaction failure about three weeks after the earthquake. The faults length depends on whom you ask, Sherrod said. An increase of 2 means that ~1,000 times more energy is released. And being ready means being able to support yourself, your loved ones, your neighborhood for 2 weeks. Many faults have not been studied enough to know if they are active. A few miles southeast across the white-capped waves of Admiralty Bay, Lake Hancock rises and falls with the tides. We use the term deep to talk about faults and earthquakes deeper than about 18 miles. Most of the populated areas of the state have a 4080% chance of having an earthquake in the next 50 years. The southern Whidbey Island fault should be considered capable of generating large earthquakes (Ms ?? It startled Johnson that such massive faults had gone undetected for so long. Notable earthquakes in bold happened in Washington. Fir trees near the failure are tilted and indicate rotation into the lake (to the left of the photo). South Whidbey Island Fault Earthquake Scenario: 7.4 Magnitude Buildings Damaged: 320,776 Fatalities: 90 - 432 Injuries: 2,920 - 7,361 Economic Loss: $15,590,000,000 SeaTac Fault Earthquake Scenario: 7.2 Magnitude Buildings Damaged: 375,954 Fatalities: 16 - 123 Injuries: 1,394 - 3,404 Economic Loss: $13,400,000,000 Tacoma Fault These types of faults are common, but usually small. Experts have warned that UK outbreak may be around two weeks behind Italys. Deep faults can occur where two tectonic plates collide and one of the plates is forced beneath the other. This scenario was modeled on the part of the SWIF from Woodinville to just west of Whidbey Island. Geologists do not yet know how often earthquakes happen on this fault. However, we can learn which faults are active and which are inactive. Also issued a warning for the UK that the Italian chaos could come to Britain 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. The San Andreas in California, for example, left gaping scars in the Earths crust, at the surface. Earthquakes cause damage by moving and shaking the ground, sometimes for several minutes. Secure .gov websites use HTTPS Ground shaking is a hazard near the epicenter of an earthquake and also in areas far from the earthquake where amplification occurs. Scientists are not sure how far east it goes. Larger crustal faults, such as the Seattle fault and southern Whidbey Island fault zone, can produce earthquakes up to magnitude 7.5. Below you will find links to view and download hazard maps created for each jurisdiction included in the current mitigation planning process.