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 intensity, from those that are so weak that they cannot be felt, to those violent enough to propel objects and people into the air, damage critical infrastructure, and wreak destruction across entire cities. The seismic activity of an area is the frequency, type, and size of earthquakes experienced over a particular time period. The seismicity at a particular location in the Earth is the average rate of seismic energy release per unit volume. The word tremor is also used for non-earthquake seismic rumbling.
The epicenter, epicentre or epicentrum in seismology is the point on the Earth's surface directly above a hypocenter or focus, the point where an earthquake or an underground explosion originates.
The 1977 Vrancea earthquake occurred on 4 March 1977, at 21:22 local time, and was felt throughout the Balkans. It had a magnitude of 7.5, making it the second most powerful earthquake recorded in Romania in the 20th century, after the 10 November 1940 seismic event. The hypocenter was situated in the Vrancea Mountains, the most seismically active part of Romania, at a depth of 85.3 km.
The Western Quebec Seismic Zone is a seismically active area in the Ottawa Valley in Eastern Ontario and Western Quebec. The zone stretches from Montreal to Témiscaming and from Cornwall up along the Laurentian Mountains.
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 1940 Vrancea earthquake, also known as the 1940 Bucharest earthquake, occurred on Sunday, 10 November 1940, in Romania, at 03:39, when the majority of the population was at home.
The 1948 Desert Hot Springs earthquake occurred on December 4 at 3:43 p.m. Pacific Standard Time with a moment magnitude of 6.4 and a maximum Mercalli intensity of VII. The shock was felt from the central coast of California in the north, and to Baja California in the south, and came at a time when earthquake research in southern California resumed following the Second World War. It was one of two events in the 20th century that have occurred near a complex region of the southern San Andreas Fault system where it traverses the San Gorgonio Pass and the northern Coachella Valley. Damage was not severe, but some serious injuries occurred, and aftershocks continued until 1957.
The 1802 Vrancea earthquake occurred in the Vrancea Mountains of today's Romania on 26 October [O.S. 14 October] 1802, on St. Paraskeva's Day. With an estimated intensity of 7.9 on the moment magnitude scale, it is the strongest earthquake ever recorded in Romania and one of the strongest in European history. It was felt across an area of more than two million square kilometers in Eastern Europe and the Balkans, from Saint Petersburg to the Aegean Sea.
The 2011 Guerrero earthquake struck with a moment magnitude of 5.7 in southern Mexico at on 5 May. It was positioned west of Ometepec, Guerrero, with a focal depth of 24 km (14.9 mi), and was lightly felt in many adjacent areas.
The 1838 Vrancea earthquake struck the western part of Vrancea County on 23 January with a magnitude of 7.5. The seism caused extensive damage in Moldavia and Wallachia, and killed dozens of people. The earthquake occurred just 36 years after another earthquake of magnitude over 7 on Richter scale devastated the southern part of Wallachia.
The 1990 Vrancea earthquakes were three earthquakes on 30 and 31 May 1990 with magnitudes of 7.0 and 6.2 Mw that struck the Romanian county of Vrancea, on two consecutive days. Severe damage in the Bucharest-Brăila-Brașov area was reported and dozens of casualties in Romania and neighbouring Moldova, Ukraine and Bulgaria.
The 1901 Black Sea earthquakewas a 7.2 magnitude earthquake, the most powerful earthquake ever recorded in the Black Sea. The earthquake epicenter was located in the east of Cape Kaliakra, 30 kilometres (19 mi) off northeast coast of Bulgaria. The mainshock occurred at a depth of 15 km (9.3 mi) and generated a 4–5-metre (13–16 ft) high tsunami that devastated the coastal areas of Romania and Bulgaria. In Romania, the earthquake was felt not only throughout Northern Dobruja, but also in Oltenia and Muntenia, and even in southern Moldova.
The 1738 Vrancea earthquake occurred on 11 June [O.S. 31 May] 1738, during the third rule of Constantin Mavrocordat. The seism aroused great panic and is mentioned in several sources. It occurred in the lower lithospheric block, at a depth of 130 km. Its effects were violent on large areas, the hardest hit being Bucharest, where several houses and churches collapsed.
The 2014 Vrancea earthquake struck Vrancea County on 22 November 2014 at , with a moment magnitude of 5.7. The earthquake occurred at a depth of 39 kilometers and lasted for thirty seconds. On the Mercalli scale the quake registered an intensity of VI (Strong).
The 1912 Maymyo earthquake or Burma earthquake struck Burma on the morning of May 23, with an epicentre near Taunggyi and Pyin Oo Lwin in Shan State. The earthquake was initially calculated at 8.0 on the surface wave magnitude scale (Ms ) by Beno Gutenberg and Charles Francis Richter, and described by them as being one of the most remarkable seismic events in the early 1900s. Recent re-evaluation of the earthquake, however, have revised the magnitude to 7.6–7.9. It was preceded by two foreshocks on May 18 and 21 with respective intensities V and VII on the Rossi–Forel scale, while the mainshock was assigned IX. Shaking was felt throughout most of Burma, parts of Siam and Yunnan; an area covering approximately 375,000 square miles. It was one of the largest earthquakes in the country.
The 1942 Ecuador earthquake or the Guayaquil earthquake occurred on 13 May at 9:06 or 9:13 pm local time with a moment magnitude of Mw 7.9. The temblor struck the coastal (Esmeraldas) region of Manabí Province, Ecuador. It caused damage mainly to cities like Guayaquil, Portoviejo and Guaranda. More than 300 people were killed and the total cost of damage was about US$2.5 million. Ecuador's largest city Guayaquil was the most affected despite the significant distantce from the epicenter. Many reinforced concrete structures in a particular area in the city were completely destroyed, contributing to fatalities.
The 1995 Menglian earthquake or 1995 Myanmar–China earthquake occurred on 12 July at 05:46:43 local time in the Myanmar–China border region. The earthquake had an epicenter on the Myanmar side of the border, located in the mountainous region of Shan State. It registered 7.3 on the Chinese surface wave magnitude scale (Ms ) and 6.8 on the moment magnitude scale (Mw ). With a maximum Mercalli intensity assigned at VIII, the quake killed eleven people and left another 136 injured. Over 100,000 homes in both countries were destroyed and 42,000 seriously damaged. Some damage to structures were also reported in Chiang Mai and Chiang Rai, Thailand. The low death toll from this earthquake was attributed to an early warning issued prior to it happening. Precursor events including foreshocks and some seismic anomalies led to an evacuation of the area before the mainshock struck. It is thought to be one of the few successfully predicted earthquakes in history.
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, damages were 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 1983 Kaoiki earthquake struck southern Hawaii Island on the morning of November 16, 1983. Measuring Mw 6.7, it was the largest to hit the island since 1975. The epicenter was located 50 km southeast of Hilo with an approximated depth of 12 km. The shallow strike-slip earthquake was assigned a maximum intensity of IX (Violent) on the Modified Mercalli scale. 6 people were injured, widespread damage and landslides were reported across the island.
