Seismic magnitude scales are used to describe the overall strength or "size" of an earthquake. These are distinguished from seismic intensity scales that categorize the intensity or severity of ground shaking (quaking) caused by an earthquake at a given location. Magnitudes are usually determined from measurements of an earthquake's seismic waves as recorded on a seismogram. Magnitude scales vary based on what aspect of the seismic waves are measured and how they are measured. Different magnitude scales are necessary because of differences in earthquakes, the information available, and the purposes for which the magnitudes are used.
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 1966 Toro earthquake, or the 1966 Ruwenzori earthquake, occurred on March 20 at 01:42 UTC. The earthquake was located near the border between Uganda and the Democratic Republic of the Congo (DRC), to the south of Lake Albert. Some sources put the epicenter in Uganda while some put it in the Democratic Republic of the Congo. The earthquake had a magnitude of 6.8 and a maximum perceived intensity of VIII (Severe) on the Mercalli intensity scale.
The 2000 Tottori earthquake occurred on 6 October 2000, at with a moment magnitude of 6.7 and a maximum Mercalli intensity of X (Extreme). The epicenter was located in Nambu, near the border with Yasugi, Shimane. About $150 million in damage was caused, with 109,095 homes damaged or destroyed, and at least 182 people were injured.
A magnitude 5.9 earthquake struck Tanzania 27 km (17 mi) east northeast of Nsunga, Kagera Region on September 10 at a depth of 40 km (25 mi). The shock had a maximum intensity of VII (Very strong). Nineteen people were killed and 253 injured in Tanzania, while four people were killed in Kamuli and seven others were injured in the Rakai District of neighbouring Uganda.
On May 4, 2018, an earthquake with a magnitude of 6.9 struck Hawaii island in the Hawaii archipelago at around 12:33 p.m. local time. The earthquake's epicenter was near the south flank of Kīlauea, which has been the site of seismic and volcanic activity since late April of that year. According to the United States Geological Survey the quake was related to the new lava outbreaks at the volcano, and it resulted in the Hilina Slump moving about two feet. It was the largest earthquake to affect Hawaii since the 1975 earthquake, which affected the same region, killing two people and injuring another 28.
The 1969 Tulbagh earthquake occurred at 20:03:33 UTC on 29 September. It had a magnitude of 6.3 and a maximum felt intensity of VIII (Severe) on the Modified Mercalli intensity scale. It caused widespread damage in the towns of Ceres, Tulbagh and Wolseley and led to 12 deaths. The earthquake was a result of strike-slip faulting along a NW-SE trending near vertical fault plane, as shown by the focal mechanism and the distribution of aftershocks.
The Afyon Province of western Turkey was struck by an earthquake measuring 6.5 on 3 February 2002 at 10:11 local time. It had a maximum felt intensity of VIII (Severe) on the Modified Mercalli intensity scale. It damaged hundreds of buildings and caused the deaths of 44 people and a further 318 injuries.
The Nemuro-Oki earthquake in scientific literature, occurred on June 17 at 12:55 local time. It struck with an epicenter just off the Nemuro Peninsula in northern Hokkaidō, Japan. It measured 7.8–7.9 on the moment magnitude scale (Mw ), 8.1 on the tsunami magnitude scale (Mt ) and 7.4 on the Japan Meteorological Agency magnitude scale (MJMA ).
The 2020 Kashgar earthquake, also known as the Jiashi earthquake occurred on 19 January 2020 at 21:27:56 China Standard Time in Xinjiang Province, China. According to the United States Geological Survey, the earthquake had a moment magnitude of 6.0 and a surface-wave magnitude of 6.4 according to the China Earthquake Network Center. It struck at a shallow depth of 5.6 km according to the USGS while the CENC has the figure at 16 km. Local emergency management agencies said the earthquake damaged more than 1,000 homes and businesses in the nearby populated towns and villages. One person is known to have died while two other children were injured.
The 1941 Sa'dah earthquake or the Jabal Razih earthquake occurred on January 11 in Razih District of the Mutawakkilite Kingdom of Yemen. The earthquake had a surface-wave magnitude of 5.8–6.5 and a shallow focal depth. Despite the moderate size of this earthquake, an estimated 1,200 people perished and at least 200 injured. With a maximum MSK-64 intensity assigned at VIII, it destroyed many villages and collapsed homes in the region of North Yemen.
The 2021 South Sandwich Islands earthquakes were a pair of powerful earthquakes, followed by many strong aftershocks which struck along the South Sandwich Trench in August 2021. The quakes measured 7.5 and 8.1 on the moment magnitude scale, according to the United States Geological Survey. The mainshock is tied with another event in 1929 as the largest earthquake ever recorded in the South Atlantic region, and is tied with the 2021 Kermadec Islands earthquake as the second largest earthquake of 2021.
The 2016 Alboran Sea earthquake struck offshore, north northeast of Al Hoceïma, Morocco in the Strait of Gibraltar on 25 January at 04:22:02 UTC, or roughly 05:22:02 West Africa Time. At its strongest in the Alboran Sea, the earthquake measured 6.3–6.4 on the moment magnitude scale (Mw ) at a shallow hypocenter depth of 12 km (7.5 mi). Assigned a maximum Modified Mercalli scale intensity of VI (Strong), the earthquake caused one fatality, injuries to at least 30 persons, and moderate damage in Morocco and Spain.
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.
The 1954 Sofades earthquake struck central Greece on 30 April 1954, at 16:02 (UTC+3). It was estimated to be 6.7–7.0 Mw and had a maximum Modified Mercalli intensity of X (Extreme). More than 25 people died, 717 were injured and about 28,000 structures were damaged or destroyed.
Western Henan and southern Shanxi in northern China were struck by an earthquake of estimated magnitude 6.8 on 23 October 1815. The epicentre was in Pinglu County in southernmost Shanxi, which was the worse affected area. It had a maximum felt intensity of IX (violent) on the Modified Mercalli scale. It caused the collapse of many houses and cave dwellings and led to the deaths of at least 13,000 people.
The 1870 Charlevoix earthquake occurred on 20 October in the Canadian province of Quebec. It had a moment magnitude of 6.6 Mw and a Modified Mercalli intensity rating of X (Extreme). The town of Baie-Saint-Paul was seriously damaged by the event, with the loss of six lives. Effects from the earthquake were felt as far as Virginia and along the New England coast of the United States.
The 1955 Lanao earthquake struck Lanao del Sur on April 1 at 02:17 local time. The earthquake measuring 7.4 on the moment magnitude scale and assigned a maximum intensity of VIII (Severe) on the Modified Mercalli intensity scale was one of the largest to hit Mindanao. It caused immense damage around the northern and central parts of Mindanao, as well as the southern reaches of Visayas. It killed at least 465 individuals and injured a further 898.
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.
Starting late September 2024, central Ethiopia experienced a series of earthquakes, most of which were located in the Awash Fentale region, and mainly located between or around the volcanoes of Mount Fentale and Dofan, in Ethiopia's Awash National Park. The earthquakes were widely felt across much of central Ethiopia, with many of them causing localized but severe damage.
