An earthquake – also called a quake, tremor, or temblor – is the shaking of the Earth's surface resulting from a sudden release of energy in the lithosphere that creates seismic waves. Earthquakes can range in intensity, from those so weak they cannot be felt, to those violent enough to propel objects and people into the air, damage critical infrastructure, and wreak destruction across entire cities. The seismic activity of an area is the frequency, type, and size of earthquakes experienced over a particular time. The seismicity at a particular location in the Earth is the average rate of seismic energy release per unit volume.
The 1872 Owens Valley earthquake – also known as the Lone Pine earthquake – struck on March 26 at in the Owens Valley, with the epicenter near the town of Lone Pine. Its magnitude has been estimated at 7.4 to 7.9, with a maximum Mercalli Intensity of X (Extreme). It was one of the most powerful earthquakes to hit California in recorded history and was similar in strength to the 1906 San Francisco earthquake. Twenty-seven people were killed and fifty-six were injured.
The 2001 Nisqually earthquake occurred at on February 28, 2001, and lasted nearly a minute. The intraslab earthquake had a moment magnitude of 6.8 and a maximum Mercalli intensity of VIII (Severe). The epicenter was in the southern Puget Sound, northeast of Olympia, but the shock was felt in Oregon, British Columbia, eastern Washington, and Idaho. This was the most recent of several large earthquakes that occurred in the Puget Sound region over a 52-year period and caused property damage valued at $1–4 billion. One person died of a heart attack and several hundred were injured.
The Okanogan–Wenatchee National Forest is a U.S. National Forest located in Okanogan County in north-central Washington, United States.
The New Madrid seismic zone (NMSZ), sometimes called the New Madrid fault line, is a major seismic zone and a prolific source of intraplate earthquakes in the Southern and Midwestern United States, stretching to the southwest from New Madrid, Missouri.
Lake Chelan is a narrow, 50.5 mi (81.3 km) long lake in Chelan County, north-central Washington state, U.S. It is an overdeepened lake and resembles a fjord, with an average width of 1.3 mi (2.1 km). Near its upper end, the lake surface lies more than 6,600 ft (2,000 m) below peaks less than 3 mi (4.8 km) away. Before 1927, Lake Chelan was the largest natural lake in the state in terms of both surface area and water volume. Upon the completion of Lake Chelan Dam in 1927, the elevation of the lake was increased by 21 ft (6.4 m) to its present maximum-capacity elevation of 1,100 ft (340 m).
Wenatchee National Forest is a U.S. National Forest located in Washington. With an area of 1,735,394 acres, it extends about 137 miles along the eastern slopes of the Cascade Range of Washington, USA from Okanogan National Forest to Gifford Pinchot National Forest. The forest is located in Chelan, Kittitas and Yakima counties.
Lake Chelan National Recreation Area is a national recreation area located about 35 miles (56 km) south of the Canada–US border in Chelan County, Washington. It encompasses an area of 61,958 acres (25,074 ha) including the northern end of Lake Chelan and the surrounding area of the Stehekin Valley and the Stehekin River. The area is managed by the U.S. National Park Service as part of the North Cascades National Park Service Complex.
The Calaveras Fault is a major branch of the San Andreas Fault System that is located in northern California in the San Francisco Bay Area. Activity on the different segments of the fault includes moderate and large earthquakes as well as aseismic creep. The last large event was the magnitude 6.2 1984 Morgan Hill event. The most recent moderate earthquakes were the magnitude 5.1 event on 25 October 2022, and the magnitude 5.6 2007 Alum Rock event.
The 1976 Guatemala earthquake struck on February 4 at with a moment magnitude of 7.5. The shock was centered on the Motagua Fault, about 160 km northeast of Guatemala City at a depth of 5 kilometers (3.1 mi) near the town of Los Amates in the department of Izabal.
The Chelan River is a tributary of the Columbia River, in the U.S. state of Washington. Just 4.1 miles (6.6 km) long, it is the shortest river in Washington. Lake Chelan Dam is located at the river's source: the outlet of Lake Chelan. Nearly the entire river's flow is diverted to the Lake Chelan Powerhouse, 3.9 miles (6.3 km) downstream near the river's mouth. Thus the Chelan River is almost always dry. Statistics on the streamflow are taken at the tailrace of the powerhouse, measuring the water that would flow through the river were it not diverted, although not including small tributaries, including Daybreak Canyon, that join the Chelan riverbed from the Lake Chelan Dam to the canal outlet.
The Okanagan Country, also known as the Okanagan Valley, is a region located in the Canadian province of British Columbia and the U.S. state of Washington, defined by the basin of Okanagan Lake and the Okanagan River. With an estimated 400,000 residents, the Okanagan Country spans from the Thompson Plateau near Grindrod, British Columbia in the Okanagan to the Okanagan Highland near Douglas County, Washington in the Okanogan. The largest city in the Canadian portion is Kelowna, with a metropolitan population of 222,162 residents as of 2021, while the largest city in the American portion is Omak, with 4,860 residents as of 2020. The region took its current name in honor of the Okanagan term, ukʷnaqín. The mild climate and close proximity to lakes, rivers and mountainous regions make the Okanagan Country an outdoor recreational destination. The region's economy is dominated by the primary sector industries of agriculture and forestry, although economic diversification has also occurred with retirement communities and recreational tourism. The American portion is considered to be more remote than the Canadian division, with approximately 10 percent of the population.
Buckner Mountain is a tall peak in the North Cascades of Washington state and in the Stephen Mather Wilderness of North Cascades National Park. At 9,114 feet (2,778 m) in elevation it is the highest in Skagit County and one of about ten of Washington's non-volcanic peaks above 9,000 feet high. It is ranked as the 14th highest peak in the state, and the third highest peak in North Cascades National Park.
The 1986 Chalfant Valley earthquake struck southern Mono County near Bishop and Chalfant, California at Pacific Daylight Time on July 21. With a moment magnitude of 6.2 and a maximum Mercalli intensity of VI (Strong), the shock injured two people and caused property damage estimated at $2.7 million in the affected areas. There was a significant foreshock and aftershock sequence that included a few moderate events, and was the last in a series of three earthquakes that affected southern California and the northern Owens Valley in July 1986.
The Brawley Seismic Zone (BSZ), also known as the Brawley fault zone, is a predominantly extensional tectonic zone that connects the southern terminus of the San Andreas Fault with the Imperial Fault in Southern California. The BSZ is named for the nearby town of Brawley in Imperial County, California, and the seismicity there is characterized by earthquake swarms.
The 1872 North Cascades earthquake occurred at in central Washington Territory. A maximum Mercalli intensity of VIII (Severe) was assessed for several locations, though less intense shaking was observed at many other locations in Washington, Oregon, and British Columbia. Some of these intermediate outlying areas reported V (Moderate) to VII shaking, but intensities as high as IV (Light) were reported as far distant as Idaho and Montana. Due to the remote location of the mainshock and a series of strong aftershocks, damage to structures was limited to a few cabins close to the areas of the highest intensity.
The 1931 Zangezur earthquake occurred on April 27 at with a moment magnitude of 6.5. The earthquake was located in the Zangezur Mountains near the boundary between southwestern Armenia and Azerbaijan's exclave, the Nakhichivan Autonomous Republic. Both territories were part of the Soviet Union at that time.
The 2014 Washington wildfires were a series of 1,480 wildfires that burned 386,972 acres (1,566 km2) over the course of 2014. The first occurred primarily on the east side of the Cascade Range in Chelan and Okanogan counties. The fires burned private land, state land, and within the Okanogan and Wenatchee National Forests, ultimately covering over 350,000 acres. The first fire began on July 8 near the Entiat River. On July 14 a lightning storm started dozens more fires across the eastern Cascade Range. Governor Jay Inslee declared a state of emergency, activating the Washington National Guard. More lightning strikes later in the summer started additional fires.
The 1968 Borrego Mountain earthquake occurred on April 8, at 18:28 PST in the geologically active Salton Trough of Southern California. The Salton Trough represents a pull-apart basin formed by movements along major faults. This region is dominated by major strike-slip faults one of them being the San Jacinto Fault which produced the 1968 earthquake. The mainshock's epicenter was near the unincorporated community of Ocotillo Wells in San Diego County. The moment magnitude (Mw ) 6.6 strike-slip earthquake struck with a focal depth of 11.1 km (6.9 mi). The zone of surface rupture was assigned a maximum Modified Mercalli intensity (MMI) of VII.
On November 22, 2014, at 22:08 local time, an earthquake struck southeast of Hakuba, Nagano Prefecture. It had a magnitude of 6.2 according to the United States Geological Survey, with a maximum intensity assigned IX (Violent) on the Modified Mercalli intensity scale. According to the Japan Meteorological Agency, it is recorded as 6.7 and at its peak intensity at Shindo 6 Lower on the Japan Meteorological Agency seismic intensity scale. The earthquake did not result in any deaths, however 41 people sustained mild to severe injuries.
