He combed through state and federal data to understand the risks, and to help train first responders. Most of the populated areas of the state have a 4080% chance of having an earthquake in the next 50 years. Expect and help to extinguish fires. The fault, not so much. 1 NE 7th Street On a frigid, blustery day in December 2018, Sherrod revisited the site where he conducted much of his field work. Avoid stopping near or under buildings, trees, overpasses, or utility wires. Why is Strange Sounds focusing so much on disaster preps? Photo by G.K. Gilbert, from the Steinbrugge Collection of the UC Berkeley Earthquake Engineering Research Center. So they dont necessarily know the threats they face.. endobj The height difference likely was caused by a 7.5 magnitude earthquake on the fault about 2,700 years ago, Sherrod said. This fundamental tool for earth scientists, maps show map units, faults and folds, cross sections, and other regional or local features, depending on map scale. Like a sonogram, the seismic surveys allowed Johnson to see outlines of massive fissures in the earths crust. 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 . PDF Seismic Characterization of the Seattle and Southern Whidbey Island Also, very large earthquakes were difficult to measure accurately. The tsunami becomes taller as the ocean becomes shallow. Earthquakes can trigger landslides and tsunamis which can happen after the main event. The South Whidbey Island Fault and Darrington Devil's Mountain Fault bound the Everett Basin. Scientists have been trying to understand how often earthquakes happen for over 100 years. You have entered an incorrect email address! Here, were looking at one of the bigger faults in the region, he said. The medic said colleagues were becoming sick and emotionally overwhelmed Over time, fault movement has created some interesting geologic features. Some people in places like SODO and Harbor Island may have to flee to higher floors in a building. Charles Richter and Beno Gutenberg discovered that for every magnitude of earthquake, there are about ten times more earthquakes of the next lower magnitude. Then the world rattles up and down. At a downtown coffee shop, the mugs begin to chatter. 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. Geologists and geophysicists at the Washington Geological Survey map out these areas of amplification to help reduce damage during an earthquake. Oblique convergence and clockwise rotation along the continental margin are the inferred driving forces for ongoing deformation. 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 In Washington, the risk from earthquake-induced landslides is large. If you are in bed: STAY there and COVER your head and neck with a pillow. For example, a M7 earthquake releases 32 times more energy than a M6 earthquake, and 1,000 times more than a M5 earthquake. After large earthquakes there are usually many aftershock earthquakes. Ground shaking is a hazard near the epicenter of an earthquake and also in areas far from the earthquake where amplification occurs. . Emergency Management Hazard Maps - Island County, Washington The map is from a 2007 report (click here to download) on seismic design categories in Washington. Prepare to be on your own for at least three days. Much of the land along the southwestern part of the lake cracked and subsided. Contact Us, Whidbey Office Someone screams. Below you will find links to view and download hazard maps created for each jurisdiction included in the current mitigation planning process. In much of Washington, dense vegetation covers the land and makes finding faults very difficult. <> Save my name, email, and website in this browser for the next time I comment. These types of faults are common, but usually small. Photo by Steve Palmer. 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. . A reverse fault occurs when two blocks are pushed together and one moves up and over the other. Devils Mountain Fault -- Online Professional Paper - USGS For example, the Cascadia subduction zone has had between 15 to 19 earthquakes over the past 10,000 years. This is similar to how sound is quieter when you move away from a speaker. For each increase in earthquake magnitude, there are about 10 times fewer earthquakes. 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. Stay inside until the shaking stops and it is safe to go outside. Radiocarbon ages of macrofossils constrain uplift timing to 2.83.2 ka. After a large earthquake it is common to have other large earthquakes for hours, days, and even weeks. Consider whether earthquake insurance is right for you. Later movement on this long-term active fault zone cut the volcano. The crustal faults the Seattle Fault, the South Whidbey Island Fault, the Tacoma Fault those are less well known, said Forson. endobj There must be tsunami deposits of the same age along much of the Oregon and Washington coast in order to qualify as an earthquake. Because they can travel great distances, tsunamis generated from earthquakes across the ocean can still cause damage. The last major earthquake was over 300 years ago. The Cascadia subduction zone last ruptured over 300 years ago on January 26, 1700. The faults length depends on whom you ask, Sherrod said. You can look at different geological hazard mapson the website of the Department of Natural Resources. Because they rupture at such great depth, their seismic energy is distributed over a large area. #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. (360) 678-5111 Do you know what to do if there is an earthquake? Tsunamis are a common result of large earthquakes in Washington. 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). 2 0 obj <>>> But scientists theorize that the area has suffered only four . Fir trees near the failure are tilted and indicate rotation into the lake (to the left of the photo). Johnson et al. Black squares are urban sewer outfalls, which don't match the bubble plumes' locations. Learn about at-risk areas and become prepared. This map is from a 2007 report on the seismic design categories in Washington. The San Andreas fault in California is a good example of a very active strike-slip fault. 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. Evacuate to higher ground if you are near a large body of water. Once a fault is located, it is important to know if it is active. The Seattle Fault is also likely to create a tsunami that would inundate Harbor Island and much of SODO, Interbay, and the waterfront. Share sensitive information only on official, secure websites. Oil companies descended in search of riches. 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. Secure .gov websites use HTTPS These quakes are capable of magnitudes from 7 to over 9. The affiliate sales will help us to continue the hard work we are putting in this website. The boundary between the two plates covers a large area and can lock together. The southern Whidbey Island fault: An active structure in the Puget Lowland Washington, Geological Society of America Bulletin 1996;108;334-354. 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. That place is the Ocosta School. An official website of the United States government. and the Red Cross will be there to care for them. Others, like the Seattle fault and southern Whidbey Island fault zone, cross under major cities and pose a significant hazard. The last time was 1,000 years ago between 900 and 903 A.D., said Forson. Reverse faults are usually steep and occur in regions of compression. In some areas getting up a hill to higher ground will be difficult. 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. What are the most dangerous fault lines for Seattle? And what were looking at is water.. There are also tsunami evacuation signs on the highways. The best thing you can do is to become prepared. California Geological Survey. The Moment Magnitude Scale (M) measures the total amount of seismic energy (known as moment to engineers and seismologists) released by an earthquake. In places where there is little vegetation, different rock types and faults can be found with relative ease. Southern Whidbey Island Fault Zone Mapped through Snoqualmie Valley Scientists are not sure how far east it goes. Both types of faults can cause ground shaking during an earthquake and may cause permanent deformation of the ground. 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. You just need one person to crash or a power line to fall over the road, and the roads are unusable.. Finding and mapping these faults is an important mission of the Washington Geological Survey. The next earthquake is inevitable, but the variability makes it difficult to know exactly when. 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. The Mercalli Intensity scale is another historical way to measure the intensity of an earthquake. Make an emergency response plan for you and your family. Other faults are inactive and are left over from much older periods of deformation. The publication Faults and Earthquakes in Washington State is a state-wide compilation of active faults and folds. When an earthquake happens there will not be time to google what you are supposed to do. By finding the age of the deformed layer, a paleoseismologist can determine the minimum age of the fault. 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. 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. 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). A community meeting about a shelter at the Harbor Inn may have yielded more questions than answers. Seconds later, its as if Whidbey Island is trapped in a cocktail shaker, lurching back and forth. This means that when the Seattle fault ruptures the south side of the fault moves up relative to the north side. Brick chimneys cascade off rooftops. This was a problem because no two locations would agree on the size of the same earthquake. Because after a region-wide event, it could take that long for help to come from the rest of the country and world. Many low-lying areas have wet soil or sediment beneath them that could liquefy during earthquakes. This might include flammable appliances like a water heater, tall items like book cases, or heavy pictures. The northwestern part of the fault zone forms the northeastern limit of the Port Townsend basin (Brocher and others, 2001 #4718). But opting out of some of these cookies may affect your browsing experience.
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