The term intraplate earthquake refers to a variety of earthquake that occurs within the interior of a tectonic plate; this stands in contrast to an interplate earthquake, which occurs at the boundary of a tectonic plate. Intraplate earthquakes are often called "intraslab earthquakes," especially when occurring in microplates.
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 1886 Charleston earthquake in South Carolina occurred about 9:50 p.m. local time August 31. It caused 60 deaths and $5–6 million in damage to 2,000 buildings in the Southeastern United States. It is one of the most powerful and damaging earthquakes to hit the East Coast of the United States.
The Wabash Valley is a region located in sections of both Illinois and Indiana. It is named for the Wabash River and, as the name is typically used, spans the middle to the middle-lower portion of the river's valley and is centered at Terre Haute, Indiana. The term Wabash Valley is frequently used in local media in Clinton, Lafayette, Mount Carmel, Princeton, Terre Haute, and Vincennes all of which are either on or near the Lower Wabash River.
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.
In the early morning hours of August 16, 1931, a powerful earthquake occurred in West Texas with a maximum Mercalli intensity of VIII (Severe). Estimates of its magnitude range between 5.8–6.4 mb, making it the most powerful earthquake ever recorded in Texas history. Its epicenter was near the town of Valentine, Texas; there, the earthquake caused damage to many homes and buildings. The earthquake may have been caused by movement along oblique-slip faulting in West Texas, the most seismically-active region in the state. Shaking from the earthquake was perceptible within a 400 mi (640 km) radius of the epicenter, affecting four U.S. states and northern Mexico. Several foreshocks and aftershocks accompanied the primary temblor, with the aftershocks continuing until at least November 3, 1931. The main earthquake caused no fatalities, though several people sustained minor injuries; the damage in Valentine amounted to $50,000–$75,000.
The 1968 Illinois earthquake was the largest recorded earthquake in the U.S. Midwestern state of Illinois. Striking at 11:02 am on November 9, it measured 5.4 on the Richter scale. Although no fatalities occurred, the event caused considerable structural damage to buildings, including the toppling of chimneys and shaking in Chicago, the region's largest city. The earthquake was one of the most widely felt in U.S. history, largely affecting 23 states over an area of 580,000 sq mi (1,500,000 km2). In studying its cause, scientists discovered the Cottage Grove Fault in the Southern Illinois Basin.
The 1868 Hawaii earthquake was the largest recorded in the history of Hawaiʻi island, with an estimated magnitude of 7.9 and a maximum Mercalli intensity of X (Extreme). The earthquake occurred at 4 p.m. local time on April 2, 1868 and caused a landslide and tsunami that led to 77 deaths. The aftershock sequence for this event has continued up to the present day.
In seismology, doublet earthquakes – and more generally, multiplet earthquakes – were originally identified as multiple earthquakes with nearly identical waveforms originating from the same location. They are now characterized as single earthquakes having two main shocks of similar magnitude, sometimes occurring within tens of seconds, but sometimes separated by years. The similarity of magnitude – often within 0.4 magnitude – distinguishes multiplet events from aftershocks, which start at about 1.2 magnitude less than the parent shock and decrease in magnitude and frequency according to known laws.
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 1887 Sonora earthquake occurred at 22:13 UTC on 3 May in the Teras mountain range of northwestern Mexico. It was widely felt, with some damage being recorded up to 200 kilometers (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 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 2014 Murmuri earthquake occurred on August 18 in the Zagros Mountains of Iran with a moment magnitude of 6.2 and a maximum Mercalli intensity of VIII (Severe). The thrust earthquake injured 60–330 people and was followed by a number of high intensity aftershocks.
The 1918 San Jacinto earthquake occurred in extreme eastern San Diego County in Southern California on April 21 at . The shock had a moment magnitude of 6.7 and a maximum Mercalli intensity of IX (Violent). Several injuries and one death occurred with total losses estimated to be $200,000.
The 2020 Central Idaho earthquake occurred in the western United States on March 31, 2020, at 5:52 PM MDT, near Ruffneck Peak in the Sawtooth Mountains of central Idaho, 72 miles (116 km) northeast of Boise and 19 miles (31 km) northwest of Stanley. It had a magnitude of 6.5 and was felt with a maximum intensity of VIII.
In 1954, the state of Nevada was struck by a series of earthquakes that began with three magnitude 6.0+ events in July and August that preceded the Mw 7.1–7.3 mainshock and M 6.9 aftershock, both on December 12. All five earthquakes are among 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 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.
The 1979 Saint Elias earthquake occurred near noon local time on the 28th of February. It measured Mw 7.4–7.6. Though the maximum recorded Modified Mercalli intensity was VII, damage was minimal and there were no casualties due to the remoteness of the faulting. The epicenter lies near the Alaskan border between America and Canada.
The 1895 Charleston earthquake, also known as the Halloween earthquake, occurred on October 31, at 05:07 CST near Charleston, Missouri. It had an estimated moment magnitude of 5.8–6.6 and evaluated Modified Mercalli intensity of VIII (Severe). The earthquake caused substantial property damage in the states of Missouri, Illinois, Ohio, Alabama, Iowa, Kentucky, Indiana, and Tennessee. Shaking was widespread, being felt across 23 states and even in Canada. At least two people died and seven were injured.
