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. It was formed by a transform boundary.
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.
The Hayward Fault Zone is a geologic fault zone capable of generating destructive earthquakes. This fault is about 74 mi (119 km) long, situated mainly along the western base of the hills on the east side of San Francisco Bay. It runs through densely populated areas, including Richmond, El Cerrito, Berkeley, Oakland, San Leandro, Castro Valley, Hayward, Union City, Fremont, and San Jose.
The Garlock Fault is a left-lateral strike-slip fault running northeast–southwest along the north margins of the Mojave Desert of Southern California, for much of its length along the southern base of the Tehachapi Mountains.
Cape Mendocino, approximately 200 miles (320 km) north of San Francisco, is located on the Lost Coast entirely within Humboldt County, California, United States. At 124° 24' 34" W longitude, it is the westernmost point on the coast of California. The South Cape Mendocino State Marine Reserve and Sugarloaf Island are immediately offshore, although closed to public access due to their protected status. Sugarloaf Island is cited as California's westernmost island.
The 1999 Düzce earthquake occurred on 12 November at with a moment magnitude of 7.2 and a maximum Mercalli intensity of IX (Violent), causing damage and at least 845 fatalities in Düzce, Turkey. The epicenter was approximately 100 km (62 mi) to the east of the extremely destructive 1999 İzmit earthquake that happened a few months earlier. Both strike-slip earthquakes were caused by movement on the North Anatolian Fault.
The Nemaha Ridge is located in the Central United States. It is a buried structural zone associated with a granite high in the Pre-Cambrian basement that extends from approximately Omaha, Nebraska to Oklahoma City, Oklahoma. The ridge is associated with the seismically active Humboldt Fault zone. It is also associated with the Proterozoic Midcontinent Rift System, which extends into northern Kansas about fifty miles west of the Nemaha.
The 1888 North Canterbury earthquake occurred at 4:10 am on 1 September following a sequence of foreshocks that started the previous evening, and whose epicentre was in the North Canterbury region of the South Island of New Zealand. The epicentre was approximately 35 kilometres (22 mi) west of Hanmer.
The 2009 Shizuoka earthquake occurred with a magnitude of 6.4 that hit Shizuoka Prefecture in the south of Honshū, Japan, on August 11 at 05:07 local time.
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 miles (53 km) 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.
The 1867 Manhattan earthquake struck Riley County, Kansas, in the United States on April 24, 1867 at 20:22 UTC, or about 14:30 local time. The strongest earthquake to originate in the state, it measured 5.1 on a seismic scale that is based on an isoseismal map or the event's felt area. The earthquake's epicenter was near the town of Manhattan.
The 1887 Sonora earthquake occurred at 22:13 UCT on 3 May in the Teras mountain range of northwestern Mexico. It was widely felt, with some damage being recorded up to 200 kilometres (120 mi) from the epicenter in both Mexico and the United States. The earthquake had an estimated magnitude of 7.6 and caused 42 casualties in the town of Bavispe and 51 overall. It was the only historical earthquake to cause considerable damage in Arizona. The 1887 Tombstone Arizona newspapers mentioned lesser quakes (aftershocks) on August 27, 1887, and November 11, 1887.
The 1797 Riobamba earthquake occurred at 12:30 UTC on 4 February. It devastated the city of Riobamba and many other cities in the Interandean valley, causing between 6,000–40,000 casualties. It is estimated that seismic intensities in the epicentral area reached at least XI (Extreme) on the Mercalli intensity scale, and that the earthquake had a magnitude of 7.6–8.3, the most powerful historical event known in Ecuador. The earthquake was studied by Prussian geographer Alexander von Humboldt, when he visited the area in 1801–1802.
The Oklahoma earthquake swarms are an ongoing series of human activity-induced earthquakes affecting central Oklahoma, southern Kansas, northern Texas since 2009. Beginning in 2009, the frequency of earthquakes in the U.S. state of Oklahoma rapidly increased from an average of fewer than two 3.0+ magnitude earthquakes per year since 1978 to hundreds each year in the 2014–17 period. Thousands of earthquakes have occurred in Oklahoma and surrounding areas in southern Kansas and North Texas since 2009. Scientific studies attribute the rise in earthquakes to the disposal of wastewater produced during oil extraction that has been injected more deeply into the ground.
The 1980 Eureka earthquake occurred on November 8 at along the northern coastal area of California in the United States. With a moment magnitude of 7.3 and a maximum Mercalli intensity of VII, this strike-slip earthquake was the largest to occur in California in 28 years. Although damage was considered light, several loss estimates equaled or exceeded $2 million, and six injuries resulted when two vehicles came down with the partial collapse of a highway overpass on US 101 in Fields Landing. The north coast of California experiences frequent plate boundary earthquakes near the Mendocino Triple Junction and intraplate events also occur within the Gorda Plate.
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.
In 1954, the state of Nevada was struck by a series of earthquakes that began with three M 6.0+ events in July and August that preceded the M 7.3 mainshock and M 6.9 aftershock, both on December 12. All five earthquakes remain some of the largest in the state, and the largest since the Cedar Mountain earthquake of 1932 and Pleasant Valley event in 1915. The earthquake was felt throughout much of the western United States.
The 2021 Antelope Valley earthquake was a magnitude 6.0 earthquake that struck near the city of Coleville, California, located in the Antelope Valley, near the border with Nevada on July 8, 2021. It was the largest earthquake to occur in California since the 2019 Ridgecrest earthquake almost exactly 2 years prior.
