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. Because they rupture at such great depth, their seismic energy is distributed over a large area. 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). Tsunamis and seiches can also be triggered by large slides, both on land and underwater. Maps. An abrupt rise or decline in sea level would reveal if the fault had triggered a quake before. The 1964 M9.2 Alaska earthquake created a large tsunami from the fault rupture, and many smaller tsunamis from on-land and underwater landslides. ; (5) large-scale liquefaction features in upper Quaternary sediments within the fault zone; and (6) minor historical seismicity. Depending on the type of fault, the ground can move laterally, vertically, or a combination of both. The last time was 1,000 years ago between 900 and 903 A.D., said Forson. Paleoseismologists have found places that record many of these tsunami deposits. PDF The Cottage Lake Aeromagnetic Lineament: a Possible Onshore Extension Quaternary Rupture of a Crustal Fault beneath Victoria, British Some people in places like SODO and Harbor Island may have to flee to higher floors in a building. This evidence can come from finding something younger than 12,000 years that has been deformed or moved by the fault. 4 0 obj Since the last ice age, the southern Whidbey Island fault zone has probably spawned several highly destructive shallow earthquakes. This is called liquefaction and is discussed in the next section. South Whidbey Island Fault Zone. 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. As an example, parts of Seattle and certain areas of downtown Olympia are built on softer ground that will amplify ground shaking during an earthquake. Most injuries occur when people inside change rooms or try to leave the building. After the shaking stopped the sand regained its strength. EVERETT The South Whidbey Island Fault is connected to a system of powerful earthquake fault lines stretching from Victoria, B.C., to Yakima that is capable of unleashing a devastating. The process of breaking and moving rock releases a large amount of energy that travels through the Earth as seismic waves. Earthquakes on faults like these may cause tsunamis in the Puget Sound region. 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. Photo from, Liquefaction can be a big problem. These aftershocks can last for hours to weeks or months. Later movement on this long-term active fault zone cut the volcano. Using the stratigraphic column from the Freeport quadrangle map, confirm that you can recognize . The Geologic Information Portal has a Natural Hazards theme that shows active faults and earthquakes. 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. Oblique convergence and clockwise rotation along the continental margin are the inferred driving forces for ongoing deformation. 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. His team wanted to find the rate of sea level rise along the shore. There are many other active faults in Washington and any of these could produce a large earthquake in the future. Buildings could sustain extensive damage. Reverse faults are usually steep and occur in regions of compression. Source: United States Geological Survey. Scientists are not sure how far east it goes. This map is from a 2007 report on the seismic design categories in Washington. 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. Coupeville, WA 98239, Main Line: Learn about at-risk areas and become prepared. The publication Faults and Earthquakes in Washington State is a state-wide compilation of active faults and folds. 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 best thing you can do is to become prepared. But quiet period wont last, Strongest earthquake in 40 years rattle residents of Buffalo, NY, Is Istanbul next? The Richter scale was developed in southern California in 1935 and was based on the local ground motion. 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. Avoid stopping near or under buildings, trees, overpasses, or utility wires. (360) 678-5111 The friend obliged. Oil companies descended in search of riches. Earthquake Hazard Maps | Sound Seismic Roads, bridges, or ramps may have been damaged by the earthquake. 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. Watch the video below to learn how you can be ready for the next earthquake. North Anatolian Fault is currently locked, accumulating stresses which could be suddenly released anytime now like the Hayward Fault in California, Videos: New destructive M7.5 earthquake hits Turkey a few hours after largest quake in 100 years kills 1300. America is going to be punished just like the rest of the world. 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. People who look for evidence of past movement on faults are usually called paleoseismologists (from paleo-ancient and seismologist-one who studies earthquakes). The Seattle Fault is also likely to create a tsunami that would inundate Harbor Island and much of SODO, Interbay, and the waterfront. The buildings in this photo were built on soft materials that liquefied during the 1964 Niigata earthquake in Japan. Wagner and Wiley (1983 #6230) and Wagner and Tomson (1987 #6249) mapped and briefly discussed offshore parts of this fault zone and also used the name "southern Whidbey Island fault." Nearly all earthquakes occur on faults, features in the Earth where rocks move past each other. We use cookies on our website to give you the most relevant experience by remembering your preferences and repeat visits. Photo by G.K. Gilbert, from the Steinbrugge Collection of the UC Berkeley Earthquake Engineering Research Center. Below you will find links to view and download hazard maps created for each jurisdiction included in the current mitigation planning process. That place is the Ocosta School. Since about 1870 there have been about 15 large earthquakes (greater than M5) in the state. In the late 1960s, speculators considered the Puget Sound region a frontier for petroleum exploration. Photo courtesy of MOHAI (neg. 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 It might as well have been sitting in a drawer, Johnson said. It is a qualitative scale that ranges from IXI (1-11) and measures the amount of damage caused by an event. Electricity, water, natural gas, and phones may not work. The plate that is forced down can have faults within it that still rupture and produce earthquakes. 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). This is sometimes called "The Big One" by news media. Swarm of hundreds of small earthquakes rattle Vancouver Island. PDF Modeling a Magnitude 7.4 Earthquake on the Western Section of the Finding nothing of serious monetary value, the companies abandoned reams of information they had gathered through seismic surveys. The boundary between the two plates covers a large area and can lock together. PDF Seismic Characterization of the Seattle and Southern Whidbey Island Theyre FREE CLICK HERE to subscribe, EAR TO THE GROUND WITH DNR & COMMISSIONER FRANZ, Tree Link helps you answer questions about urbantrees. The shaking can damage or destroy buildings and other infrastructure. Both of these things can cause equal or greater damage than the actual earthquake. The Seattle fault last ruptured about 1,100 years ago in AD 900950. This averages to ~660 to 525 years between events, but there is a lot of variation. Never use a lighter or match near damaged areas. Armentrout, J. J. Miller, C. Finn, C. S. Weaver. An increase of 2 means that ~1,000 times more energy is released. There must be tsunami deposits of the same age along much of the Oregon and Washington coast in order to qualify as an earthquake. Do you know what to do if there is an earthquake? Some faults reach the surface and can be found by geologists. Many landslide-prone areas of Washington are also located near active faults. In Seattle, the quake damaged buildings, weakened bridges, started fires and opened cracks in the earth. Were working on pedestrian evacuation maps that show the best routes for pedestrians to take to evacuate, said Forson. This fault zone was originally named the Devils Customers lift their eyes from phone screens. PDF Cretaceous-Jurassic accreted terrains - University of Washington Large earthquakes, like those from the Cascadia subduction zone on January 26, 1700, often create tsunamis. In the 1990s, scientists producedan animationthat shows inundation, and people wont have much time to run to higher ground. Consider subscribing to our blog, Washington State Geology News, to receive notifications when new information is published. The trenches exposed glacial deposits disrupted by faults and liquefaction features. Earthquakes occur nearly every day in Washington. Charles Richter and Beno Gutenberg discovered that for every magnitude of earthquake, there are about ten times more earthquakes of the next lower magnitude. <>>> While the intensity of this seismic event has now decreased, a big earthquake is overdue in the region. You saw its potential in the 9.1 magnitude Tohuku earthquake and tsunami that hit northeastern Japan in March 2011. Johnson, on a whim, acquired the data that would prove its existence beyond a doubt.

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