Some parts of major cities (including Seattle, Tacoma, and Olympia) have been built on land that was reclaimed from soft and wet tidal ocean areas. One or possibly two of the unconformities are interpreted as event horizons. These older faults do not have any evidence for recent activity, but the Earth is always changing. 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 spectacular falls flow over the remains of a newly discovered 20-million-year-old volcano, apparently formed atop the main part of the fault zone as magma rose upward along weak fault planes. Doorways do not provide protection from falling or flying objects and you may not be able to remain standing. Scientists have been trying to understand how often earthquakes happen for over 100 years. The publication Faults and Earthquakes in Washington State is a state-wide compilation of active faults and folds. Story telling is an important part of the Native tradition and is how their history is passed down to the next generation. 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 Seattle fault is a good example of a fault that is mostly reverse. A damaging earthquake is inevitable on this fault, but we do not know exactly when it will happen. The last time was 1,000 years ago between 900 and 903 A.D., said Forson. In some areas getting up a hill to higher ground will be difficult. 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. 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. Photo from Pacific Northwest Seismic Network Seismo Blog. This is an active fault.. Since about 1870 there have been about 15 large earthquakes (greater than M5) in the state. 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. Mudslides. When the ground shakes during an earthquake, it moves up and down, acting like additional gravity. 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. Roads, bridges, or ramps may have been damaged by the earthquake. One of the best views of SWIF should be from Grand Avenue Park in Everett. 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. PI22343). Finding and mapping these faults is an important mission of the Washington Geological Survey. After the shaking stopped the sand regained its strength. Fault Activity Map of California. In fact, new faults are found every year during our geologic mapping efforts. In places where there is little vegetation, different rock types and faults can be found with relative ease. The western half of Washington state is considered earthquake country, with the potential for very large quakes. Prepare to be on your own for at least three days. Once we got it, we were sort of shocked to see these big faults in the Puget lowlands, he said. The Mercalli Intensity scale is another historical way to measure the intensity of an earthquake. 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. But opting out of some of these cookies may affect your browsing experience. Reverse faults are usually steep and occur in regions of compression. A drill rig left of the blockade is collecting data about the failure. But the mapping offered geological clues that the newly found fault was indeed capable of future quakes. The trenches exposed glacial deposits disrupted by faults and liquefaction features. We also use third-party cookies that help us analyze and understand how you use this website. This is similar to how sound is quieter when you move away from a speaker. When an earthquake happens there will not be time to google what you are supposed to do. In Washington, we do not have tsunami walls. 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 boundary between the two plates covers a large area and can lock together. These sediments were laid down 20,000 to 60,000 years ago, before the last ice age. California Department of Conservation. Knowing how often large earthquakes have happened in the past helps us to know how often they might occur in the future. Many landslide-prone areas of Washington are also located near active faults. Tsunamis and seiches are destructive waves which can be triggered by certain types of large earthquakes. Close to shore, this same wave could reach heights of 30100 feet or more. The last major earthquake was over 300 years ago. Its just the way scientists work, he said. 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. Though it was not directly related to Johnsons work, he asked a friend working for Mobil Oil to pass along the information. Swarm of hundreds of small earthquakes rattle Vancouver Island. A magnitude 7.4 along the southern Whidbey fault would rattle 18 counties in Washington, according to a federal projection . This fault produces some of the largest and most damaging earthquakes in the world (M9). Johnson and others (1996) have described the southern Whidbey Island fault ( figure 1) as a broad (6 - 11 km) transpressional zone comprising three main splays, within which the local late Quaternary uplift rate is at least 0.6 mm/yr. You can look at different geological hazard mapson the website of the Department of Natural Resources. The Cascadia subduction zone just off the Washington coast is this kind of fault and is one of the largest geologic hazards to our state. Why is Strange Sounds focusing so much on disaster preps? Buildings could sustain extensive damage. After the shaking stopped the sand regained its strength. Sherrods son has since completed graduate school in applied geosciences. East of Puget Sound, the SWIF makes landfall between the cities of Seattle and Everett but is concealed . Ground shaking is a hazard near the epicenter of an earthquake and also in areas far from the earthquake where amplification occurs. endobj Consider whether earthquake insurance is right for you. Deformed recessional outwash deposits and Holocene deposits were exposed; three unconformities separated the units. Expect aftershocks. 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). Seconds later, its as if Whidbey Island is trapped in a cocktail shaker, lurching back and forth. These aftershocks can last for hours to weeks or months. HomePrograms and ServicesGeologyGeologic Hazards. You saw its potential in the 9.1 magnitude Tohuku earthquake and tsunami that hit northeastern Japan in March 2011. 1 NE 7th Street 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. For example, a M7 earthquake releases 32 times more energy than a M6 earthquake, and 1,000 times more than a M5 earthquake. Then the world rattles up and down. During the shaking liquefaction occurred, the sand lost its strength, and the car sunk. These combination faults are called oblique faults and include the Seattle fault, southern Whidbey Island fault zone, and DarringtonDevils Mountain fault zone. In the early 2000s, USGS scientists including Brian Sherrod set out to further Johnsons work and better understand the slumbering fissure. . Southeast Extension of the Southern Whidbey Island Fault By Human Capital March 19, 2019. sw_whidbeyfault_rev122706.pdf (28.68 KB) While the intensity of this seismic event has now decreased, a big earthquake is overdue in the region. Brick chimneys cascade off rooftops. 1 0 obj Were working on pedestrian evacuation maps that show the best routes for pedestrians to take to evacuate, said Forson. Secure .gov websites use HTTPS Larger crustal faults, such as the Seattle fault and southern Whidbey Island fault zone, can produce earthquakes up to magnitude 7.5. Source: United States Geological Survey. Some residents may lose housing temporarily or permanently. The map also shows potentially active faults from a separate 2014 report (click here to download). Finding and learning about faults requires many different aspects of geology and geophysics. This map is from a 2007 report on the seismic design categories in Washington. This website uses cookies to improve your experience while you navigate through the website. For example, it is unlikely that you will be able to use electricity, cell phones, or the internet. Many low-lying areas have wet soil or sediment beneath them that could liquefy during earthquakes. In this sense, the shaking of the ground is the sound of rocks breaking and moving deep within the Earth. This kind of grouping gives us information about how common earthquakes might be and how large an area may be affected. Someone screams. 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. And when are documentary film called Cascadia The Big One, Dangerous Inland Earthquake Destroys Homes and Schools near Jakarta, Indonesia, Terrifying video shows olive grove turned into a Gigantic Canyon after Turkeys earthquake split land in huge rifts. Photo from https://buildingfailures.files.wordpress.com/2014/02/tiltedbuilding.jpg. The buildings in this photo were built on soft materials that liquefied during the 1964 Niigata earthquake in Japan. Keaton and Perry (2006 #7653) excavated two trenches on the south end of the Brightwater treatment plant (KP1 site 572-3, and KP2 site 572-4). Official websites use .gov Geologists at the Survey spend time mapping the geology of the state, looking for faults, folds, landslides, and different rock types. Landslide at Salmon Beach was triggered by the 1949 Tacoma earthquake and caused a tsunami. Share sensitive information only on official, secure websites. Theres approximately a 14% chance of another approximately M9 earthquake occurring in the next 50 years. This scenario was modeled on the part of the SWIF from Woodinville to just west of Whidbey Island. document.getElementById( "ak_js_1" ).setAttribute( "value", ( new Date() ).getTime() ); This site uses Akismet to reduce spam. ?7) and represents a potential seismic hazard to residents of the Puget Lowland. Scientists have used the stories from tribes along the entire Pacific Northwest coast to learn that the last large earthquake on the Cascadia subduction zone was about AD 1700. The shaking can also cause landslides, surface ruptures, ground cracks, liquefaction, tsunamis, and seiches (standing waves). These large underwater slides only occur during very large earthquakes and are one way to learn about earthquakes that happened thousands of years ago. This kind of landslide is called an earthquake-triggered landslides. Geologists have used the location of these shallow, intermediate, and deep earthquakes to learn about subduction zones throughout the world. Not all faults are active. Visit our School Seismic Safety page for more information. These faults and earthquakes occur in oceanic crust as it is subducted beneath the continent. Each of the earthquakes listed on the bottom of the screen is capable of significant damage. 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. Its certainly not to scare you. 3 0 obj This date was confirmed by records in Japan of an orphan tsunami and by many lines of geologic evidence. South Whidbey Island Fault Zone. The map also shows potentially active faults from a separate 2014 report (click here to download). The moment magnitude scale replaced the Richter scale in the late 1970s. 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. The more you know what to expect, the better prepared you will be to help yourself, your family, and others around you. 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. People who look for evidence of past movement on faults are usually called paleoseismologists (from paleo-ancient and seismologist-one who studies earthquakes). Additionally, because the continent moves up and over the ocean plate, large amounts of sea water are displaced and cause damaging tsunamis. The southern Whidbey Island fault represents a segment of a boundary between two major crustal blocks. Graphic from IRIS. 4 0 obj 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. Power could be out for days. <>/XObject<>/ExtGState<>/Pattern<>/ProcSet[/PDF/Text/ImageB/ImageC/ImageI] >>/MediaBox[ 0 0 612 792] /Contents 4 0 R/Group<>/Tabs/S/StructParents 0>> 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. 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. This means that a tsunami made by an earthquake on the Cascadia subduction zone will start to impact the Washington coast in less than 15 minutes. 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. The best thing you can do is to become prepared. Both of these things can cause equal or greater damage than the actual earthquake. Along the coast residents may have between 20 and 30 minutes to get to higher ground. Faults are features in the Earths crust where rock periodically breaks and moves, releasing seismic energy and creating an earthquake. Earthquakes on faults like these may cause tsunamis in the Puget Sound region. Do you live or work near an area that could have liquefaction? Liquefaction has caused significant damage during earthquakes in Washington. 2 0 obj Southeast Extension of the Southern Whidbey Island Fault, Washington: Implications for Earthquake Hazards, 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). By clicking Accept, you consent to the use of ALL the cookies. The Geologic Information Portal has a Natural Hazards theme that shows active faults and earthquakes. Electricity, water, natural gas, and phones may not work. This category only includes cookies that ensures basic functionalities and security features of the website. Although we cannot predict exactly when the next earthquake will happen, we can predict the general distribution of earthquake sizes. Transpressional deformation along the southern Whidbey Island fault is indicated by alongstrike variations in structural style and geometry, positive flower structure, local unconformities, out-of-plane displacements, and juxtaposition of correlative sedimentary units with different histories. 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. Some of these faults are in remote areas. 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. Hundreds could die, with thousands more injured. Until much more recently, no one really understood what it could do to a region of over 4 million people. California Geological Survey. Avoid stopping near or under buildings, trees, overpasses, or utility wires. Black lines show the South Whidbey Island Fault Zone, the Seattle Fault Zone and the Tacoma Fault Zone. Higher risk areas are in orange and lower risk areas are in green.