Peak ground acceleration (PGA) is equal to the maximum ground acceleration that occurred during earthquake shaking at a location. PGA is equal to the amplitude of the largest absolute acceleration recorded on an accelerogram at a site during a particular earthquake. Earthquake shaking generally occurs in all three directions. Therefore, PGA is often split into the horizontal and vertical components. Horizontal PGAs are generally larger than those in the vertical direction but this is not always true, especially close to large earthquakes. PGA is an important parameter for earthquake engineering, The design basis earthquake ground motion (DBEGM) is often defined in terms of PGA.
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 2006 Greece earthquake – also known as the Kythira earthquake – occurred on January 8 at 13:34:53 local time and was felt throughout the entire eastern Mediterranean basin. The earthquake an magnitude 6.7 and a maximum Mercalli intensity of VII. Its epicentre was located just off the island of Kythira about 200 kilometres (120 mi) south of Athens.
The Cameroon line is a 1,600 km (1,000 mi) long chain of volcanoes that includes islands in the Gulf of Guinea and mountains on the African mainland, from Mount Cameroon on the coast towards Lake Chad on the northeast. They form a natural border between eastern Nigeria and the West Region of Cameroon. The islands, which span the equator, have tropical climates and are home to many unique plant and bird species. The mainland mountain regions are much cooler than the surrounding lowlands, and also contain unique and ecologically important environments.
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 1991 Racha earthquake occurred in the province of Racha, Georgia, at 9:12 UTC on 29 April. Centered on the districts of Oni and Ambrolauri on the southern foothills of the Greater Caucasus mountains, it killed 270, left approximately 100,000 homeless and caused severe damage, including to several medieval monuments. It had a magnitude of 7.0 and was the most powerful earthquake recorded in the Caucasus.
The 1949 Olympia earthquake occurred on April 13 at with a moment magnitude of 6.7 and a maximum Mercalli Intensity of VIII (Severe). The shock was located in the area between Olympia and Tacoma, and was felt throughout the state, as well as parts of Oregon, British Columbia, Idaho, and Montana. It is the largest recorded earthquake to occur in the Puget Sound region of Washington. Eight people were killed, a minimum of 64 people were injured, and the total damage is estimated at $25 million.
The 1983 Borah Peak earthquake occurred on October 28, at in the western United States, in the Lost River Range at Borah Peak in central Idaho.
The 1995 Neftegorsk earthquake occurred on 28 May at on northern Sakhalin Island in the Russian Far East. It was the most destructive earthquake known within the current state of Russia, with a magnitude of 7.1 and maximum Mercalli intensity of IX (Violent) that devastated the oil town of Neftegorsk, where 1,989 of its 3,977 citizens were killed, and another 750 injured.
The 1982 North Yemen earthquake hit near the city of Dhamar, North Yemen on December 13. Measuring 6.2 on the moment magnitude scale, with a maximum perceived intensity of VIII (Severe) on the Mercalli intensity scale, as many as 2,800 people were killed and another 1,500 injured. The shock occurred within several hundred kilometers of a plate boundary in a geologically complex region that includes active volcanoes and seafloor spreading ridges. Yemen has a history of destructive earthquakes, though this was the first instrumentally recorded event to be detected on global seismograph networks.
On 13 March 1992, a moment magnitude 6.7 earthquake struck eastern Turkey. It had a maximum Mercalli intensity of IX (Violent) and occurred along the North Anatolian Fault. At least 498 people died, roughly 2,000 were injured, and an unknown number of people went missing. Total financial losses were between $13.5 million and $750 million.
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 1746 Lima–Callao earthquake occurred at on 28 October with a moment magnitude of 8.6–8.8 and a maximum Mercalli intensity of XI (Extreme). The epicenter was located about 90 km (56 mi) north-northwest of the capital Lima, which was almost completely destroyed, and the subsequent tsunami devastated the port city of Callao. It was the deadliest earthquake in Peru's history prior to the 1970 earthquake.
The 1989 Chenoua earthquake occurred on October 29 at in northern Algeria. The dip-slip event had a moment magnitude of 5.9 and a maximum Mercalli intensity of VIII (Severe). At least 22 were killed and many were injured with total losses of $5 million.
The 1930 Bago (Pegu) earthquake, also known as the Swa earthquake struck Myanmar on 5 May. The moment magnitude (Mw ) 7.4 earthquake had a focal depth of 35 km (22 mi) and maximum Rossi–Forel intensity of IX. The earthquake was the result of rupture along a 131 km (81 mi) segment of the Sagaing Fault—a major strike-slip fault that runs through the country. Extensive damage was reported in the southern part of the country, particularly in Bago and Yangon, where buildings collapsed and fires erupted. At least 550, and possibly up to 7,000 people were killed. A moderate tsunami was generated along the Burmese coast which caused minor damage to ships and a port. It was felt for over 570,000 km2 (220,000 sq mi) and as far as Shan State and Thailand. The mainshock was followed by many aftershocks; several were damaging; additional earthquakes occurred in July and December, killing dozens. The December earthquake was similarly sized which also occurred along the Sagaing Fault.
The 1604 Arica earthquake is an earthquake that occurred at 1:30 pm on November 24, 1604, offshore Arica, Chile. The estimated magnitude range is 8.0–8.5 and up to 8.7–9.0 and 8.8–9.0. It had a destructive tsunami that destroyed moust of Southern Peru, including Arica and Arequipa. 1,200–2,800 km (750–1,740 mi) of coastline was affected by the tsunami. The recorded effects of this earthquake are very similar to those for the 1868 Arica event, suggesting a similar magnitude and rupture area of the megathrust between the subducting Nazca plate and the overriding South American plate. Tsunami deposits have been identified on the Chatham Islands that are likely to have been caused by a trans-Pacific tsunami caused by the 1604 earthquake.
The 1983 Hindu Kush earthquake occurred south of Fayzabad, Badakhshan in northeast Afghanistan at 03:52 PST on December 31, 1983, near the border with Pakistan and the USSR. Striking 214.5 km beneath the Hindu Kush mountains, the moment magnitude 7.4 quake affected three countries, killing at least 26 people and injuring several hundred.
On 30 November 1973, at 07:48 UTC, a Mw 4.7 earthquake struck 1 km (0.62 mi) north-east of Alcoa, in the U.S. state of Tennessee. The earthquake was felt 2,100 km2 (810 sq mi) in the area. It was the most powerful known earthquake generated by the Eastern Tennessee Seismic Zone.
