southern whidbey island fault map
This is a very good example of a strike-slip fault. These cookies will be stored in your browser only with your consent. Once a fault is located, it is important to know if it is active. Even if the earthquake is too small to be felt by people, seismographs can detect it. Once we got it, we were sort of shocked to see these big faults in the Puget lowlands, he said. (1999 . In the 1990s, scientists producedan animationthat shows inundation, and people wont have much time to run to higher ground. The SWIF has been assessed by the USGS as capable of generating the largest crustal earthquake in Puget Sound. Geologists do not yet know how often earthquakes happen on this fault. Along the coast residents may have between 20 and 30 minutes to get to higher ground. Scientists at the Washington Geological Survey, the U.S. Geological Survey, universities, and many private geologic consulting firms work diligently to understand how often earthquakes happen on various faults throughout Washington. Faulting produced warping at the site of greater than 2 m. Radiocarbon ages provide a maximum age for the folding event of 12,09011,670 cal yr BP. Despite its location well offshore, a Cascadia quake would likely kill at least 10,000 and injure more than 30,000 in Washington, Murphy found. Even when an earthquake happens on a fault that doesnt reach the surface, the ground can still show signs of cracking. This car was parked on sand during the 2011 earthquake in Christchurch, New Zealand. The Cascadia subduction zone last ruptured over 300 years ago on January 26, 1700. 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. 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. The Seattle fault is a good example of a fault that is mostly reverse. But it didnt. 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 southern Whidbey fault is shallow, running right under Snohomish County as opposed to many miles off shore like the Cascadia fault. After the earthquake, many things you count on may not be available. These faults and earthquakes usually occur at great depth (tens to hundreds of miles). The Flying Squirrel and Mountain Beaver trenches cross the Cottage Lake lineament. 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. It startled Johnson that such massive faults had gone undetected for so long. Doctor reveals the horrors Italian medics are facing in overwhelmed hospitals where dying patients are being left untreated as experts warn UK and US are just two weeks behind Italy and the public are not SCARED enough, An intensive care doctor in northern Italy has described the scale of the crisis The map is from a, This car was parked on sand during the 2011 earthquake in Christchurch, New Zealand. That may not sound like much more than the magnitude 6.8 quake of 2001 based on the numbers, but that the Nisqually quake occurred some 30 miles underground. Drop, Cover, and Hold On whenever you feel shaking. (360) 678-5111 The moment magnitude scale is a type of logarithmic scale, where each increase of 1 means ~32 times more energy is released. Some of these faults are in remote areas. Since the last ice age, the southern Whidbey Island fault zone has probably spawned several highly destructive shallow earthquakes. If you are in bed: STAY there and COVER your head and neck with a pillow. The Seattle fault last ruptured about 1,100 years ago in AD 900950. Coupeville, WA 98239, Camano Office Emergency planners all had a simple message: Its not IF a disaster will happen, its WHEN. This was a problem because no two locations would agree on the size of the same earthquake. Tohoku killed nearly 16,000 people; most died as a result of drowning or being crushed in the tsunami. Do you live or work near an area that could have liquefaction? Some faults reach the surface and can be found by geologists. A major southern Whidbey quake, on the other hand, could kill and injure many more, according to Murphy. Though it was not directly related to Johnsons work, he asked a friend working for Mobil Oil to pass along the information. Here, were looking at one of the bigger faults in the region, he said. Sometimes Geologists can use the offset land surface to understand how much the fault moved during the earthquake. When earthquakes occur on faults that reach the Earths surface, the ground may rupture. Liquefaction can be a big problem. Stratigraphy and diatom assemblages of the marsh cores suggest Crockett Marsh underwent a 12 m of abrupt uplift relative to sea level at a time that relative sea level remained the same at Hancock Marsh. Like a sonogram, the seismic surveys allowed Johnson to see outlines of massive fissures in the earths crust. Stories from tribes near Seattle have also helped us to learn that the last earthquake on the Seattle fault was about AD 900950. Everything points to one thing, Sherrod said, waving his hand across the inland sea. Learning earthquake faults around where we live is a first good way to prepare the next devastating earthquake. Washington has few large normal faults because it is mostly in a region of compression. Photo by Steve Palmer. These differences are related to the overall pattern of stress in the crust, what types of rocks the crust is made from, and how many faults there are. %PDF-1.5 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. Sherrods son has since completed graduate school in applied geosciences. His team wanted to find the rate of sea level rise along the shore. Earthquakes on shallow faults typically last 20 to 60 seconds and the shaking is localized to the general area of the fault. The Richter scale was developed in southern California in 1935 and was based on the local ground motion. Each of the earthquakes listed on the bottom of the screen is capable of significant damage. Restoring tap water to some homes could take over a year. Even places that are far from active faults are still at risk during a large Cascadia subduction zone earthquake. ; (5) large-scale liquefaction features in upper Quaternary sediments within the fault zone; and (6) minor historical seismicity. California Geological Survey. In this sense, the shaking of the ground is the sound of rocks breaking and moving deep within the Earth. Stop as quickly as safety permits and stay in the vehicle. 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 paleoseismologist will look for surface ruptures along faults and may use carbon-14 dating to learn when the rupture happened. Each of these aftershocks would be a significant earthquake if it happened on its own. The Mercalli Intensity scale is another historical way to measure the intensity of an earthquake. 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. This is sometimes called "The Big One" by news media. The term active can have different meanings. The buildings in this photo were built on soft materials that liquefied during the 1964 Niigata earthquake in Japan. When an earthquake happens there will not be time to google what you are supposed to do. Finding faults and knowing how often they rupture is one of the most important tasks to keep society safe from these hazards. If everyone tries to use their cell phones, it can overload the system. So they dont necessarily know the threats they face.. Johnson and others (1996 #4751) described multiple sub-parallel strands and referred to the overall structure as the "southern Whidbey Island fault zone," and this name is also used herein for this zone of faults that crosses the southern part of Whidbey Island. On Dec. 15th, a small swarm even hit near Bremerton, a few miles away from downtown. The buildings in this photo were built on soft materials that liquefied during the 1964 Niigata earthquake in Japan. These include (from north to south, see map) the: Devils Mountain Fault Strawberry Point and Utsalady Point faults Southern Whidbey Island Fault (SWIF) Rogers Belt (Mount Vernon Fault/Granite Falls Fault Zone) Cherry Creek Fault Zone Rattlesnake Mountain Fault Zone Seattle Fault Tacoma Fault Saddle Mountain Faults But Forson says you also need to know what to do when the shaking happens. This map of Puget Sound shows the location of the methane plumes (yellow and white circles) detected along the ship's path (purple). Both of these things can cause equal or greater damage than the actual earthquake. Bookcases and china cabinets topple, trapping people beneath. These and other problems led to the search for a scale that was based on the physical processes that happen during an earthquake. The Cascadia subduction zone off the Washington and Oregon coast is capable of some of the largest earthquakes in the world. The trenches exposed glacial deposits disrupted by faults and liquefaction features. Lidar maps show the Earths surface without vegetation. These older faults do not have any evidence for recent activity, but the Earth is always changing. 552 - Hood Canal fault zone (Class B) 570 - Seattle fault zone 572 - Southern Whidbey Island fault zone 575 - Saddle Mountain faults 581 - Tacoma fault zone. The map is from a 2007 report (click here to download) on seismic design categories in Washington. The experts say few are ready. For each increase in earthquake magnitude, there are about 10 times fewer earthquakes. The more you know what to expect, the better prepared you will be to help yourself, your family, and others around you. We just dont know when.. 1 NE 7th Street Because Japan was so well prepared, mostretrofitted buildingsoutside of the tsunami zone survived. It can also make landslides that are much bigger than expected. The biggest one is called the South Whidbey Island fault, and it's thought to run from Victoria, B.C., through Woodinville and possibly beyond. In the month after the main earthquake there were about 60 M7 and M6 earthquakes. Because they need large earthquakes that move the ocean floor, tsunamis are most commonly made by subduction zone faults like those found off the coasts of the Pacific Northwest, Japan, and Chile. There are also many faults that have not been studied enough to know if they are active. These sediments were laid down 20,000 to 60,000 years ago, before the last ice age. Faults can also be grouped based on what part of the crust they occur in. Hundreds could die, with thousands more injured. Geoscientist Brian Sherrod stands near the submerged southern Whidbey Island fault line at the Brightwater Treatment Plant in Woodinville. Know what to expect. In the Puget Sound region, it takes a trained eye to recognize rocky outcrops and subtly raised ground as evidence of a fault. Map Releases; Topographic (Topo) Maps; Volcanic Maps; All Maps; Multimedia Gallery. PO Box 5000 The faults length depends on whom you ask, Sherrod said. Evidence for Quaternary movement on the southern Whidbey Island fault includes (1) offset and disrupted upper Quaternary strata imaged on seismic-reflection profiles; (2) borehole data that suggests as much as 420 m of structural relief on the Tertiary-Quaternary boundary in the fault zone; (3) several meters of displacement along exposed faults in upper Quaternary sediments; (4) late Quaternary folds with limb dips of as much as ???9?? The most recent hit roughly 2,700 years ago. In Washington, the risk from earthquake-induced landslides is large. After large earthquakes there are usually many aftershock earthquakes. One model suggests it extends to about 30 miles east of Yakima. Videos: Strong M6.0 earthquake rattles Mindanao in the Philippines, Dramatic earthquake increase in Hawaii! Earthquakes between 45 and 185 miles deep are called intermediate, and earthquakes over 185 miles deep are called deep. When the ground shakes during an earthquake, it moves up and down, acting like additional gravity. of Earth and Space Sciences, Box 351310, Univ. The Darrington-Devils Mountain fault zone is located in southern Skagit County and northern Snohomish County. These combination faults are called oblique faults and include the Seattle fault, southern Whidbey Island fault zone, and DarringtonDevils Mountain fault zone. Third, the South Whidbey Island Fault running from northwest to southeast of the southern tip of the island. For example, a M7 earthquake releases 32 times more energy than a M6 earthquake, and 1,000 times more than a M5 earthquake. Black lines show the South Whidbey Island Fault Zone, the Seattle Fault Zone and the Tacoma Fault Zone. The team also found that accumulated movement on the fault has uplifted old Snoqualmie River sediments to their current position on ridges, in some places several hundreds of feet above the modern Snoqualmie valley floor. Expect aftershocks. Consider a magnitude 7.4 quake with Whidbey Island at or near the epicenter. Scientists are not sure how far east it goes. 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 2011 Tohoku earthquake in Japan occurred on this type of fault and released enough energy to slightly change the Earths axis of rotation. 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. PI22343). 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. He combed through state and federal data to understand the risks, and to help train first responders. The Survey works to increase public and scientific understanding of fault and earthquake hazards in our state. After a large earthquake it is common to have other large earthquakes for hours, days, and even weeks. The April 1949 Tacoma earthquake measured 7.1 on the Richter Scale and caused damage from southern Oregon to British Columbia. The shaking usually lasts less than a minute and doesnt generally cause a tsunami or have many aftershocks. But scientists theorize that the area has suffered only four . Make an emergency response plan for you and your family. Drop to your hands and knees. The publication Faults and Earthquakes in Washington State is a state-wide compilation of active faults and folds. 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. Small talk stops. Each peak of the Olympics stuck out with picturesque clarity in the distance. This photo shows a fence that was offset about 8.5 feet during the 1906 Great San Francisco Earthquake on the San Andreas fault. The Eastern Sierra fault along the east side of the Sierra Nevada mountains in California is a good example of an active normal fault. Save my name, email, and website in this browser for the next time I comment. So the fault remained mostly a mystery until the 1990s. Someone screams. (1996) used seismic-reflection profiles in Puget Sound near Whidbey Island, sea-cliff exposures on Whidbey Island, and sparse borehole data to map and interpret the SWIF as a broad fault zone (6 to 11 km wide) dipping steeply to the northeast. Evacuate to higher ground if you are near a large body of water. Higher risk areas are in orange and lower risk areas are in green. The map also shows potentially active faults from a separate 2014 report (click here to download). Still think well avoid Gods wrath, its not going to happen regardless of what the multi millionaire TV preachers tell you. Coupeville, WA 98239, Main Line: % Buildings could sustain extensive damage. In Seattle, the quake damaged buildings, weakened bridges, started fires and opened cracks in the earth. Most are too small to be felt or cause damage. Additionally, because the continent moves up and over the ocean plate, large amounts of sea water are displaced and cause damaging tsunamis. Earthquakes can trigger landslides and tsunamis which can happen after the main event. Also check out Ear to the Ground, published by the Department of Natural Resources. This means that the internet, your cell phone, grocery stores, and gas stations may also not work. Scientists have also dated large underwater landslides and turbidites that travel from the continental edge far out into the ocean basin. Earthquakes cause damage by moving and shaking the ground, sometimes for several minutes. It is a qualitative scale that ranges from IXI (1-11) and measures the amount of damage caused by an event. Another big one is expected, and it could be devastating. . Most of the populated areas of the state have a 4080% chance of having an earthquake in the next 50 years. Theres approximately a 14% chance of another approximately M9 earthquake occurring in the next 50 years. 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. <>/XObject<>/ExtGState<>/Pattern<>/ProcSet[/PDF/Text/ImageB/ImageC/ImageI] >>/MediaBox[ 0 0 612 792] /Contents 4 0 R/Group<>/Tabs/S/StructParents 0>> Each year we map additional areas and learn more about existing faults and (or) discover new ones. This map shows different seismic design categories that correlate with amount of seismic risk. southern Whidbey Island fault zone (Class A) No. An abrupt rise or decline in sea level would reveal if the fault had triggered a quake before. The tsunami becomes taller as the ocean becomes shallow. A half dozen people reaching for the last can of soup, someone could lose their life over that. All faults, regardless of size, can be dangerous if they rupture. The most important thing you can do before the next earthquake is to prepare. When the landslide hit the water it may have created a tsunami. And experts fear it could be even worse than The Big One.. DO NOT get in a doorway. Notice the Seattle Fault Zone bounding the Seattle Basin to the south. An increase of 2 means that ~1,000 times more energy is released. This earthquake is along the southern Whidbey Island fault, a less-known, less-studied subterranean boundary. The height difference likely was caused by a 7.5 magnitude earthquake on the fault about 2,700 years ago, Sherrod said. The map also shows potentially active faults from a separate 2014 report (click here to download). The friend obliged. The fault has at least three almost parallel strands within a 4- to 7-mile-wide band, stretching eastward from Vancouver Island. For example, the DNR team found evidence that the rocks creating Snoqualmie Falls are much younger than previously thought. The last time was 1,000 years ago between 900 and 903 A.D., said Forson. Theres an uneasy hush. These cookies do not store any personal information. These faults and earthquakes occur in the continental crust of North America. document.getElementById( "ak_js_1" ).setAttribute( "value", ( new Date() ).getTime() ); This site uses Akismet to reduce spam. The shaking can damage or destroy buildings and other infrastructure. Westport currently is the only location with a vertical evacuation structure designed for a tsunami. What scientists dont know is its timing interval. The video is also available in Spanish and there is a fun activity/coloring book that can be found here. A strike-slip fault occurs when two blocks move past each other. 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). 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. ?7) and represents a potential seismic hazard to residents of the Puget Lowland. 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. At the Washington Geological Survey, active means that a fault has evidence for movement within the Holocene time period (since about 12,000 years ago). Fault Activity Map of California. 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. That place is the Ocosta School. Roads, bridges, or ramps may have been damaged by the earthquake. For example, it is unlikely that you will be able to use electricity, cell phones, or the internet. We use cookies on our website to give you the most relevant experience by remembering your preferences and repeat visits. Finding and mapping these faults is an important mission of the Washington Geological Survey. One model suggests it extends to about 30 miles east of Yakima. Maps. In addition, the Survey performs seismic safety evaluations of schools. The fault's length depends on whom you ask, Sherrod said. It is capable of generating severe earthquakes that would impact the entire west coast. Below you will find links to view and download hazard maps created for each jurisdiction included in the current mitigation planning process. #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. 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. Large earthquakes are likely to happen in Washington during your lifetime. The coast is now the home of one of the states largest network of warning sirens called All Hazard Alert Broadcast (AHABs). If they know theres data available that could help them in any way, they want to get it. Know what other hazards you might face. Scientists dont know. Others, like the Seattle fault and southern Whidbey Island fault zone, cross under major cities and pose a significant hazard. The DNR team found that the Seattle fault is intercepted by the southern Whidbey Island fault zone in the vicinity of Fall City. The average time between large earthquakes is about 535 years, but has been as little as 200 years, and more than 1,000 years. Customers lift their eyes from phone screens. Seismic waves travel at hundreds to thousands of miles per hour and quickly reach the surface where they are felt or measured. 3 0 obj We also use third-party cookies that help us analyze and understand how you use this website. They havent dug up enough history to estimate. A seiche is a large standing wave caused by the resonance of a particular period of wave energy. When a fault with vertical movement ruptures the ocean floor, it lifts up part of the ocean. Some events appear to be only 200 years apart, and others are more than 1,000. The Straight Creek fault in the Cascade Range is an example of this kind of fault and has ~5060 miles of movement across it. East of Puget Sound, the SWIF makes landfall between the cities of Seattle and Everett but is concealed . In much of Washington, dense vegetation covers the land and makes finding faults very difficult. And what were looking at is water.. Washington has dozens of active faults and fault zones. The Geologic Information Portal has a Natural Hazards theme that shows active faults and earthquakes. But the mapping offered geological clues that the newly found fault was indeed capable of future quakes. Much of the land along the southwestern part of the lake cracked and subsided. Radiocarbon ages of macrofossils constrain uplift timing to 2.83.2 ka. For example, in the open ocean a tsunami may be less than a few feet tall. <> It may not be possible to find water, fuel, or food until services are restored days or even weeks after the event. Contact Us, Whidbey Office They didnt recognize the significance of what they found. Story telling is an important part of the Native tradition and is how their history is passed down to the next generation.
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