An earthquake is the shaking of the surface of the Earth resulting from a sudden release of energy in the Earth's lithosphere that creates seismic waves. Earthquakes can range in size from those that are so weak that they cannot be felt to those violent enough to propel objects and people into the air, and wreak destruction across entire cities. The seismicity, or seismic activity, of an area is the frequency, type, and size of earthquakes experienced over a period of time. The word tremor is also used for non-earthquake seismic rumbling.
The San Andreas Fault is a continental transform fault that extends roughly 1,200 kilometers (750 mi) through California. It forms the tectonic boundary between the Pacific Plate and the North American Plate, and its motion is right-lateral strike-slip (horizontal). The fault divides into three segments, each with different characteristics and a different degree of earthquake risk. The slip rate along the fault ranges from 20 to 35 mm /yr.
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 largest earthquakes to hit California in recorded history and was similar in size 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, Canada, 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 National Forest is a U.S. National Forest located in Okanogan County in north-central Washington, United States.
The New Madrid Seismic Zone, 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-mile (81.3 km) long lake in Chelan County, north-central Washington state, U.S. Before 1927, it was the largest natural lake in the state by any measure. Upon the completion of Lake Chelan Dam in 1927, the elevation of the lake was increased by 21 feet (6.4 m) to its present maximum-capacity elevation of 1,100 feet (340 m). Two communities lie on the southern end of the lake, and a third sits at the far north end, providing a gateway to the North Cascades National Park.
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 U.S. National Recreation Area (NRA) 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 1984 Morgan Hill event and the last moderate earthquake was the 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 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 194,882 residents as of 2016, while the largest city in the American portion is Omak, with 4,881 residents as of 2011. 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.
The Wabash Valley Seismic Zone is a tectonic region located in the Midwest of the United States, centered on the valley of the Lower Wabash River, along the state line between southeastern Illinois and southwestern Indiana.
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 state. 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 2011 Oklahoma earthquake was a 5.7 magnitude intraplate earthquake which occurred near Prague, Oklahoma on November 5 at 10:53 p.m. CDT in the U.S. state of Oklahoma. The epicenter of the earthquake was in the vicinity of several active wastewater injection wells. According to the United States Geological Survey (USGS), it was the most powerful earthquake ever recorded in Oklahoma; this record was surpassed by the 2016 Oklahoma earthquake. The previous record was a 5.5 magnitude earthquake that struck near the town of El Reno in 1952. The quake's epicenter was approximately 44 miles (71 km) east-northeast of Oklahoma City, near the town of Sparks and was felt in the neighboring states of Texas, Arkansas, Kansas and Missouri and even as far away as Tennessee and Wisconsin. The quake followed several minor quakes earlier in the day, including a 4.7 magnitude foreshock. The quake had a maximum perceived intensity of VIII (Severe) on the Mercalli intensity scale in the area closest to the epicenter. Numerous aftershocks were detected after the main quake, with a few registering at 4.0 magnitude.
The 2016 Oklahoma earthquake occurred on September 3, 2016 near Pawnee, Oklahoma. Measuring 5.8 on the moment magnitude scale, it is the strongest in state history. At 5.8 magnitude, this ties it with the 2011 Virginia earthquake, which was determined after it struck to be the most powerful quake in the eastern United States in the preceding 70 years.
The 2013 Craig, Alaska earthquake struck on January 5th, at 12:58 am (UTC–7) near the city of Craig and Hydaburg, on Prince of Wales Island. The Mw 7.5 earthquake came nearly three months after an Mw 7.8 quake struck the Queen Charlotte Islands on October 28, in 2012. The quake prompted a regional tsunami warning to British Columbia and Alaska, but it was later cancelled. Due to the remote location of the quake, there were no reports of casualties or damages.
