The Modified Mercalli intensity scale measures the effects of an earthquake at a given location. This is in contrast with the seismic magnitude usually reported for an earthquake.
The 1811–1812 New Madrid earthquakes were a series of intense intraplate earthquakes beginning with an initial earthquake of moment magnitude 7.2–8.2 on December 16, 1811, followed by a moment magnitude 7.4 aftershock on the same day. Two additional earthquakes of similar magnitude followed in January and February 1812. They remain the most powerful earthquakes to hit the contiguous United States east of the Rocky Mountains in recorded history. The earthquakes, as well as the seismic zone of their occurrence, were named for the Mississippi River town of New Madrid, then part of the Louisiana Territory and now within the U.S. state of Missouri.
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.
The 1987 Whittier Narrows earthquake occurred in the southern San Gabriel Valley and surrounding communities of Southern California, United States, at on October 1. The moderate magnitude 5.9 blind thrust earthquake was centered several miles north of Whittier in the town of Rosemead, had a relatively shallow depth, and was felt throughout southern California and southern Nevada. Many homes and businesses were affected, along with roadway disruptions, mainly in Los Angeles and Orange counties. Damage estimates ranged from $213–358 million, with 200 injuries, three directly related deaths, and five additional fatalities that were associated with the event.
The Virginia seismic zones in the U.S. state of Virginia include the Giles County seismic zone and the Central Virginia seismic zone. Earthquakes in the state are irregular and rarely reach over 4.5 in magnitude.
The 1949 Queen Charlotte Islands earthquake struck Haida Gwaii and the Pacific Northwest coast at 8:01 p.m. PDT on August 21. The earthquake had a moment magnitude of 8.0 and a surface-wave magnitude of 8.1. The maximum Mercalli Intensity in the event was VIII (Severe).
The 1983 Coalinga earthquake struck at 4:42 p.m. Monday, May 2 of that year, in Coalinga, California.
The 1909 Wabash River earthquake occurred at 04:45 local time on September 27 with a maximum Mercalli intensity of VII. It measured 5.1 on a seismic scale that is based on an isoseismal map or the event's felt area. With moderate damage in the Wabash River Valley, it is currently the strongest earthquake recorded in the U.S. state of Indiana. The earthquake occurred somewhere along a fault within the Wabash Valley seismic zone.
On November 29, 1783, at 10:50 p.m. (UTC−5), a Mfa 5.3 earthquake occurred in the U.S. state of New Jersey. It was the state's first recorded seismic event. It is estimated that the quake was the largest and strongest that the state has ever recorded. The earthquake caused intensity VII damage on the Mercalli intensity scale.
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 and 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 1944 Cornwall–Massena earthquake occurred on September 5 at 12:38:45 am EDT in Massena, New York. It registered 5.8 on the moment magnitude scale and had a maximum Mercalli intensity of VIII (Severe). This area is part of the Saint Lawrence River Valley and the seismically active zone known as the Saint Lawrence rift system. The earthquake is the largest known in New York's recorded history and was felt over great distances.
The 1984 Morgan Hill earthquake occurred on April 24 at in the Santa Clara Valley of Northern California. The shock had a moment magnitude of 6.2 and a maximum Mercalli intensity of VIII (Severe). The epicenter was located near Mount Hamilton in the Diablo Range of the California Coast Ranges. Nearby communities sustained serious damage with financial losses of at least US$7.5 million.
The 1968 Illinois earthquake was the largest recorded earthquake in the U.S. Midwestern state of Illinois. Striking at 11:02 a.m. on November 9, it measured 5.3 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 1940 New Hampshire earthquakes struck on December 20 and again on December 24. Both shocks had an estimated magnitude of 5.6, and a maximum Mercalli intensity of VII. These doublet earthquakes were the largest to hit the state in several hundred years. Damage included minor fractures or knocked over chimneys in a zone extending through New Hampshire and four other states: Maine, New York, Vermont and Massachusetts.
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 1916 Irondale earthquake struck in the north-central region of the U.S. state of Alabama on October 18. The strongest earthquake in state history, it registered an estimated Richter scale magnitude of 5.1 and resulted in minor damage. Damage was limited to Shelby and Jefferson counties and reached its maximum severity near the epicenter in the city of Irondale, including cracked windows, fallen chimneys, and dried-up wells. While there were no fatalities, the earthquake spawned widespread panic, prompting alarmed workers to evacuate tall buildings.
The 1932 Eureka earthquake occurred on June 6 at along the northern coastal area of California in the United States. With a moment magnitude of 6.4 and a maximum Mercalli intensity of VIII (Severe), this earthquake left one person dead from a falling chimney and several injured. The shock was the largest in the area since 1923 and was felt in southern Oregon and northern California.
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.
An earthquake struck near the Hawaiian island of Lanai on February 19, at 10:11 pm HST with an estimated magnitude of 7.5 on the moment magnitude scale (Mw ). It remains one of the largest seismic event to hit the Hawaiian Islands since the 1868 Kaʻū earthquake, with its effects being felt throughout the entire archipelago. It caused severe damage on the islands of Lanai, Molokai and Maui. A tsunami may have been generated however there are speculations if it had actually happened. Despite the size of the quake and the extent of damage, there were no deaths.
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.
