UTC time | 1969-02-28 02:40:32 |
---|---|
ISC event | 812637 |
USGS-ANSS | ComCat |
Local date | 28 February 1969 |
Local time | 02:40:32 |
Magnitude | 7.8 Mw [1] |
Depth | 22.0 km (13.7 mi) |
Epicenter | 36°01′01″N10°57′00″W / 36.017°N 10.950°W |
Areas affected | Portugal, Morocco |
Max. intensity | MMI VII (Very strong) |
Tsunami | 1.14 m (3 ft 9 in) [2] 3 runups [2] |
Aftershocks | 6.3 Mw Feb 28 at 04:25:35 UTC [3] |
Casualties | 13 killed [2] 80 injured [2] |
The 1969 Portugal earthquake struck western Portugal and Morocco on 28 February at 02:40 UTC. Originating west of the Strait of Gibraltar, the earthquake registered a magnitude of 7.8 and the maximum felt intensity was VII (Very strong) on the Mercalli intensity scale. In total, 13 people died and 80 sustained minor injuries. It is the largest earthquake to hit Portugal since the 1755 Lisbon earthquake. [4]
The epicenter of the earthquake lies within a diffuse zone of seismicity known as the Azores–Gibraltar seismic belt, [5] which marks the boundary between the African plate and the Eurasian plate. The deformation at this plate boundary is transpressional in style, with dextral (right lateral) strike-slip accompanied by slow convergence (4 mm/yr). [6] Linear bathymetric features within this zone, such as the SW–NE trending Gorringe Bank, are thought to be a result of reverse faulting. [5] Investigations using multibeam swathe bathymetry have revealed additional SW–NE trending reverse faults and fold axes and a set of WNW–ESE trending lineaments, interpreted as strike-slip faults. The earthquake was located within the Horseshoe Abyssal Plain, where active reverse faulting has been imaged on seismic reflection data. [7]
At magnitude 7.8, the earthquake was considered very powerful. The resulting damage killed 13 people (11 in Morocco and 2 in Portugal). Damage to local buildings was "moderate", according to the United States Geological Survey. Overall, structures were prepared for the earthquake and responded well, sustaining slight, if any, damage. [8]
The earthquake is interpreted to have resulted from movement on a southeast-dipping reverse fault. [5] Analysis of seismigrams of the earthquake revealed two subevents comprised the rupture process. The first subevent, a pure thrust-faulting mechanism, occurred during the first 15 seconds of the rupture. Twenty seconds after the rupture onset, a larger subevent occurred with a strike-slip mechanism at shallower depths, reaching the seafloor. [9]
An earthquake occurred on November 27, 2005, at 13:52 IRST on the sparsely populated Qeshm Island off Southern Iran, killing 13 people and devastating 13 villages. It was Iran's second major earthquake of 2005, following the one at Zarand in February. The epicenter was about 1,500 kilometers (930 mi) south of Tehran, close to Iran's southern borders. Initial measurements showed that the earthquake registered about 6.0 on the moment magnitude scale, although that was reduced to 5.8 after further analysis. More than 400 minor aftershocks followed the main quake, 36 of which were greater than magnitude 2.5. The earthquake occurred in a remote area during the middle of the day, limiting the number of fatalities. Iranian relief efforts were effective and largely adequate, leading the country to decline offers of support from other nations and UNICEF.
The 2006 Kamchatka earthquake occurred on April 21, 2006 at 12:25 PM local time. This shock had a moment magnitude of 7.6 and a maximum Mercalli intensity of X (Extreme). The hypocenter was located near the coast of Koryak Autonomous Okrug at an estimated depth of 22 km, as reported by the International Seismological Centre. This event caused damage in three villages and was followed by a number of large aftershocks. Two M6.6 earthquakes struck on April 29 at 16:58 UTC and again on May 22 at 11:12 UTC. These earthquakes caused no deaths; however, 40 people were reported injured.
The Queen Charlotte Fault is an active transform fault that marks the boundary of the North American plate and the Pacific plate. It is Canada's right-lateral strike-slip equivalent to the San Andreas Fault to the south in California. The Queen Charlotte Fault forms a triple junction south with the Cascadia subduction zone and the Explorer Ridge. The Queen Charlotte Fault (QCF) forms a transpressional plate boundary, and is as active as other major transform fault systems in terms of slip rates and seismogenic potential. It sustains the highest known deformation rates among continental or continent-ocean transform systems globally, accommodating greater than 50mm/yr dextral offset. The entire approximately 900 km offshore length has ruptured in seven greater than magnitude 7 events during the last century, making the cumulative historical seismic moment release higher than any other modern transform plate boundary system.
The 2004 Al Hoceima earthquake occurred on 24 February at 02:27:47 local time near the coast of northern Morocco. The strike-slip earthquake measured 6.3 on the moment magnitude scale and had a maximum perceived intensity of IX (Violent) on the Mercalli intensity scale. Between 628 and 631 people were killed, 926 injured, and up to 15,000 people were rendered homeless in the Al Hoceima-Imzourene-Beni Abdallah area.
The Dasht-e Bayaz and Ferdows earthquakes occurred in Dashte Bayaz, Kakhk and Ferdows, Iran in late August and early September 1968. The mainshock measured 7.1 on the moment magnitude scale and had a maximum perceived intensity of X (Extreme) on the Mercalli intensity scale. Damage was heavy in the affected areas with thousands of lives lost in the first event and many hundreds more in the second strong event.
The 2002 Denali earthquake occurred at 22:12:41 UTC November 3 with an epicenter 66 km ESE of Denali National Park, Alaska, United States. This 7.9 Mw earthquake was the largest recorded in the United States in 37 years. The shock was the strongest ever recorded in the interior of Alaska. Due to the remote location, there were no fatalities and only one injury.
The 1995 Antofagasta earthquake occurred on July 30 at 05:11 UTC with a moment magnitude of 8.0 and a maximum Mercalli intensity of VII. The Antofagasta Region in Chile was affected by a moderate tsunami, with three people killed, 58 or 59 injured, and around 600 homeless. Total damage from the earthquake and tsunami amounted to $1.791 million.
The 1975 North Atlantic earthquake occurred on May 26 at 09:11 UTC. The epicenter was located in the North Atlantic, in an area between the Azores, Iberian Peninsula, and Morocco. It had a magnitude of Mw 7.9, or Ms 8.1.
An earthquake occurred in southern Mongolia on December 4, 1957, measuring Mw 7.8–8.1 and assigned XII (Extreme) on the Modified Mercalli intensity scale. Surface faulting was observed in the aftermath with peak vertical and horizontal scarp reaching 9 m (30 ft). Because of the extremely sparse population in the area, this event, despite its magnitude, was not catastrophic. However, 30 people died and the towns of Dzun Bogd, Bayan-leg and Baruin Bogd were completely destroyed.
The 1969 Tulbagh earthquake occurred at 20:03:33 UTC on 29 September. It had a magnitude of 6.3 Mw 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 1979 Ghaenat earthquakes were a series of large earthquakes in Qaen County, Khorasan Province, northeast Iran, near the Afghanistan border. The first mainshock, known as the Korizan earthquake with a surface-wave magnitude (Ms ) of 6.6 and moment magnitude (Mw ) of 6.8, struck on November 14, while the Ms 7.1 or Mw 7.2 Koli-Boniabad earthquake struck on November 27. The two mainshocks were assigned a maximum Modified Mercalli intensity of VIII (Severe) and X (Extreme), respectively. The earthquakes caused extensive damage throughout northeastern Iran, killing an estimated 297 to 440 people and left at least 279 injured.
The 1998 Azores Islands earthquake struck with an epicenter in the Atlantic Ocean, off the Azores Islands of Portugal at 05:19 local time. The 10 km (6.2 mi) deep mainshock, which measured 6.1 on the moment magnitude scale caused significant damage on Faial Island. At least 10 people died, 100 were injured, and 2,500 people were left without homes.
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.
The 1969 Alaşehir earthquake occurred on March 28 at 03:48 local time near the city of Alaşehir in Turkey's Manisa Province. The Mw 6.8 earthquake struck at 10 km (6.2 mi) depth. It had a MSK 64 intensity of VIII (Destructive). At least 53 people were killed in the earthquake.
The 1997 Bojnurd earthquake occurred on 4 February at 14:07 IRST in Iran. The epicenter of the Mw 6.5 earthquake was in the Kopet Dag mountains of North Khorasan, near the Iran–Turkmenistan border, about 579 km (360 mi) northeast of Tehran. The earthquake is characterized by shallow strike-slip faulting in a zone of active faults. Seismic activity is present as the Kopet Dag is actively accommodating tectonics through faulting. The earthquake left 88 dead, 1,948 injured, and affected 173 villages, including four which were destroyed. Damage also occurred in Shirvan and Bojnord counties. The total cost of damage was estimated to be over US$ 30 million.
The 1979 Saint Elias earthquake affected Alaska at 12:27 AKST on 28 February. The thrust-faulting Mw 7.5 earthquake had an epicenter in the Granite Mountains. Though the maximum recorded Modified Mercalli intensity was VII, damage was minimal and there were no casualties due to the remoteness of the faulting. Damage also extended across the border in parts of Yukon, Canada.
The 1977 Bob–Tangol earthquake struck Kerman province of Iran on December 20, 1977, at 03:04 Iran Standard Time. The earthquake measured Mw 5.9 and struck at a depth of 22.7 km (14.1 mi). A maximum Modified Mercalli intensity of VII was evaluated based on damage. It had a strike-slip focal mechanism, which was unusual as the source structure was a thrust fault. It was part of a sequence of strong earthquakes along the 400 km (250 mi) Kuh Banan Fault. Between 584 and 665 people perished while a further 500–1,000 were injured; thousands were also made homeless. Casualties from the earthquake was considered moderate due to the sparsely populated area it affected. Preceded by foreshocks the month before, many residents became wary of a larger earthquake and took refuge outside their homes, contributing to the moderate death toll. However, there were none immediately before the mainshock so many were still in their homes when it struck. Aftershocks were felt for several months, some causing additional damage.
On 22 January 1988, a sequence of destructive earthquakes measuring 6.2, 6.3, and 6.6 struck southwest of Tennant Creek, Australia which was felt as far north as Darwin and in other regions of the country. The largest event of the sequence was the largest earthquake ever recorded in mainland Australia since records began in 1800. An intensity of IX (Violent) was observed. Despite the large magnitude of the earthquakes and a close proximity to a town, in a country where earthquakes of this size are not common, damages were limited. Thousands of aftershocks were reported and felt across Northern Territory.
The 1977 Naghan earthquake struck Chaharmahal and Bakhtiari province in Iran on April 6 at 13:36 UTC. The earthquake measuring 6.0 Mw occurred at a depth of 15 km (9.3 mi) and had a maximum Modified Mercalli intensity of VIII (Severe). More than 2,100 homes were destroyed and at least 348 people died.
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 (30 mi) southeast of Hilo with an approximated depth of 12 km (7 mi). 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.
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: CS1 maint: DOI inactive as of September 2024 (link)