The last Cascadia Megaquake occurred January 26, 1700 with an estimated moment magnitude of 8.7–9.2 and stretched from mid-Vancouver Island, south along the Pacific Northwest coast as far as northern California stretching for more than 1,000 kilometers (620 miles), with an average slip of 20 meters (66 ft), and resulted in a massive tsunamai felt as far away as Japan. This map shows the boundary between the Juan de Fuca Plate system and the North American Plate which forms the Cascadia Subduction Zone. They found similarities to faults in Chile, Alaska, and Japan's Nankai Trough, locations known for megathrust earthquakes, a conclusion that was met with skepticism from other geophysicists at the time. The Cascadia Subduction Zone (CSZ) "megathrust" fault is a 1,000 km long dipping fault that stretches from Northern Vancouver Island to Cape Mendocino California. We enjoy attribution and link backs. The Cascadia Subduction Zone is where the oceanic Juan de Fuca plate is diving underneath the North American plate. [5], In the 1980s, geophysicists Tom Heaton and Hiroo Kanamori of Caltech compared the generally quiet Cascadia to more active subduction zones elsewhere in the Ring of Fire. Lying mostly offshore, this plate interface is a giant fault—approximately 700 miles long (1,130 km). In this study, we model geodetic strain accumulation along the Cascadia subduction zone between 2007.0 and 2017.632 using position time series from 352 continuous GPS stations. The Cascadia Subduction Zone has not produced an earthquake since 1700 and is building up pressure where the Juan de Fuca Plate is subsiding underneath the North American plate. Images and content by other authors are copyright. Plate Tectonics: Seafloor Spreading, Subduction and Megathrust Earthquakes. More information and full stipulations about our Creative Commons Licence, copyrighted material and use policy, can be found in our Copyright Policy Page. In most other subduction zones, tectonic plates slide more freely and therefore have more frequent earthquakes, releasing built-up pressure more often. [6] The pair happened upon a section of "ghost forest," so-called due to the dead, gray stumps left standing after a sudden inundation of salt water had killed them hundreds of years ago. For more about the Cascadia Subduction Zone, visit the USGS webpage discussing this topic. neath the Cascadia margin at about 4 cm=yr (DeMets et al., 1990), as the ridge migrates northeastward toward the subduction zone. This finding was evidence that the ground had suddenly sunk under sea level, causing saltwater to kill the vegetation. [3], In the 1960s, underground fractures were uncovered by oil companies in Puget Sound. This fault is responsible for deep earthquakes known as Cascadia megaquakes and the active volcanism of the Cascade mountains that has shaped our region for tens of thousands of years. Unlike the other trees, these suffered from a landslide rather than a dip in the fault during a separate event around 900 CE. Plans are underway to retrieve data from these sites in summer 2021 using the USGS waveglider. Orally transmitted legends from the Olympic Peninsula area tell of an epic battle between a thunderbird and a whale. There were rings up until the year 1699, indicating that the incident had occurred shortly thereafter. Root samples confirmed their conclusion, narrowing the time frame to the winter of 1699 to 1700. "[1] Translating the Japanese calendar, Satake found the incident had taken place around midnight of 27–28 January 1700, ten hours after the earthquake occurred. It is named after the explorer of the same name. The Cascadia subduction zone is a convergent plate boundary where three small oceanic plates – the Gorda, Juan de Fuca and Explorer plates – subduct beneath the North American continental plate off the west coast of northern California, Oregon, Washington and southern British Columbia (Figure 1). Plate Tectonics: Seafloor Spreading, Subduction and Megathrust Earthquakes - YouTube. It separates the Juan de Fuca and North America plates. The event had happened so quickly that the top layer of sand sealed away the air, thus preserving centuries-old plants. One of the smallest of Earth's tectonic plates, the Juan de Fuca Plate is a remnant part of the once-vast Farallon Plate, which is now largely subducted underneath the North American Plate. They can involve 10 to 20 metres of fault movement, along the hundreds of kilometres that make up the fault line. It is part of the Earth’s famous “Ring of Fire,” created by subduction zone processes as Earth’s tectonic plates collide and move past each other. Cascadia is a tectonically active region, and the grand landscape reflects its geologic origins. Please receive permission before use. [3] Japanese annals, which have recorded natural disasters since approximately 600 CE,[1] had reports of a sixteen-foot tsunami that struck the coast of Honshu Island during the Genroku. 19.1, the Juan de Fuca and Gorda segments.The third, the Explorer segment, is off the Canadian coast. (Credit: Rob Wyland, USGS Pacific Coastal and Marine Science Center. A thick, actively de-forming accretionary wedge is forming along the base of the continental slope off Washington. 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