Title: Geology of the Pacific Northwest
Content:  The Pacific Northwest is seismically active. The Juan de Fuca Plate is capable of producing megathrust earthquakes of moment magnitude 9: the last such earthquake was the 1700 Cascadia earthquake, which produced a tsunami in Japan, and may have temporarily blocked the Columbia River with the Bonneville Slide. More recently, in 2001, the Nisqually earthquake (magnitude 6.8) struck 10 mi northeast of Olympia, Washington, causing some structural damage and panic. In addition, eleven volcanoes in Canada have had seismic activity since 1975, including: the Silverthrone Caldera, Mount Meager massif, Wells Gray-Clearwater volcanic field, Mount Garibaldi, Mount Cayley massif, Castle Rock, The Volcano, Mount Edziza volcanic complex, Hoodoo Mountain, Crow Lagoon and Nazko Cone.
Title: Pacific Northwest
Content:  The Northwest is still highly geologically active, with both active volcanoes and geologic faults. The last known great earthquake in the northwest was the 1700 Cascadia earthquake. The geological record reveals that "great earthquakes" (those with moment magnitude 8 or higher) occur in the Cascadia subduction zone about every 500 years on average, often accompanied by tsunamis. There is evidence of at least 13 events at intervals from about 300 to 900 years. Active volcanoes in the region include Mount Garibaldi, Mount Baker, Mount Rainier, Mount St. Helens, Mount Adams, Mount Hood, Mount Meager, Mount Jefferson, Mount Shasta, and Glacier Peak.
Title: Pacific Northwest Seismic Network
Content:  Damaging earthquakes are well known in the Pacific Northwest, including several larger than magnitude 7, most notably the M9 1700 Cascadia earthquake and the M7.0–7.3 earthquake in about 900AD on the Seattle Fault. The M6.5 1965 Puget Sound earthquake shook the Seattle, Washington area, causing substantial damage and seven deaths. This event spurred the installation of the Pacific Northwest Seismic Network in 1969 to monitor regional earthquake activity. Early in 1980 PNSN scientists detected unrest under Mt. St. Helens and by March 1980 predicted an eruption was likely to occur "soon". On March 27th the first steam and ash explosion occurred. The PNSN expanded to better monitor Mt. St. Helens and other Cascade Volcanos leading up to the deadly May 18 eruption and in the years following.
Title: 2019 Ridgecrest earthquakes
Content:  A large portion of the slippage between the Pacific and North American plates is accommodated in the Eastern California Shear Zone (ECSZ), resulting in many large earthquakes even within the limited span of the historical era. Most notable of these earthquakes is the 1872 Owens Valley earthquake, With an estimated magnitude of 7.4 (preferred; other estimates range as high as 7.9 ), this earthquake is believed to be the greatest earthquake on record not only for California, but for all of the western United States. In March 1946 an earthquake struck near Walker Pass (crest of the Sierra Nevada, due west from Ridgecest), with aftershocks 
Title: 1993 Scotts Mills earthquake
Content:   The 1993 Scotts Mills earthquake, also known as the "Spring break quake", occurred in the U.S. state of Oregon on March 25 at 5:34 AM Pacific Standard Time. With a moment magnitude of 5.6 and a maximum perceived intensity of VII (Very strong) on the Mercalli intensity scale, it was the largest earthquake in the Pacific Northwest since the Elk Lake and Goat Rocks earthquakes of 1981. Ground motion was widely felt in Oregon's Willamette Valley, the Portland metropolitan area, and as far north as the Puget Sound area near Seattle, Washington.
Title: 2004 in science
Content: September 28 – A long-awaited earthquake strikes Parkfield, California, the most closely monitored earthquake zone in the world. The earthquake, which had been expected to have occurred by the late 1980s, strikes at a magnitude 6.0. The network of instruments that had been installed in the region make this the most well-recorded earthquake in history. ; December 26 – Indian Ocean earthquake and tsunami. 
Title: 1949 Olympia earthquake
Content:  The 1949 Olympia earthquake occurred on April 13 at 11:55:44 local time with a moment magnitude of 6.7 and a maximum Mercalli Intensity of VIII (Severe). The shock was located in the area between Olympia and Tacoma, and was felt throughout the state, as well as parts of Oregon, British Columbia, Idaho, and Montana. It is the largest recorded earthquake to occur in the Puget Sound region of Washington. Eight people were killed, a minimum of 64 people were injured, and the total damage is estimated at $25 million.
Title: 2010 Eureka earthquake
Content:  The 2010 Eureka earthquake occurred on January 9 at 4:27:38 pm PST offshore of Humboldt County, California, United States. The magnitude was measured 6.5 on the scale, and its epicenter was located offshore in the Pacific Ocean 33 mi west of the nearest major city, Eureka. Additionally, there was a separate earthquake further offshore of Eureka on February 4 with a slightly lower magnitude of 5.9. It was also the most significant earthquake in the Eureka area in terms of magnitude since the 1992 Cape Mendocino earthquakes. It was felt from Santa Cruz County, California in the south, to Eugene, Oregon in the north and to the east as far as Reno, Nevada.
Title: 1958 Lituya Bay earthquake and megatsunami
Content:  The major earthquake that struck on the Fairweather Fault had a moment magnitude of 7.8 and a maximum perceived intensity of XI (Extreme) on the Mercalli intensity scale. The epicenter of the quake was at latitude 58.37° N, longitude 136.67° W near the Fairweather Range, 7.5 mi east of the surface trace of the Fairweather fault, and 13 mi southeast of Lituya Bay. This earthquake had been the strongest in over 50 years for this region: the Cape Yakataga earthquake, with an estimated magnitude of 8.2 on the Richter scale, occurred on September 4, 1899. The shock was felt in southeastern Alaskan cities over an area of 400000 sqmi, as far south as Seattle, Washington, and as far east as Whitehorse, Yukon, Canada.
Title: Oklahoma earthquake swarms (2009–present)
Content:  struck 28 kilometers (17 miles) northwest of Fairview. It was the third-strongest earthquake ever recorded in Oklahoma at the time it occurred. Early on the morning of September 3, a 5.8-magnitude quake struck 9.3 miles (15 km) north of Pawnee, Oklahoma, breaking the record set by the 2011 earthquake near Prague, Oklahoma for the strongest quake in the state. Though the USGS originally stated that, like the Prague quake, its magnitude was 5.6, the USGS later upgraded the magnitude of the Pawnee quake to 5.8 while simultaneously retrospectively upgrading the Prague quake to 5.7. Just as with its predecessor in 2011, this 

Question: what is the largest magnitude earthquake that has occurred in the pacific northwest?
Answer: The 1700 Cascadia earthquake.