UTC time | 1946-09-12 15:17:23 |
---|---|
1946-09-12 15:20:28 | |
ISC event | 898579 |
898580 | |
USGS-ANSS | ComCat |
ComCat | |
Local date | September 12, 1946 |
Magnitude | 7.3 Mw , 7.9 Ms [1] |
7.7 Mw , [1] 7.8 Ms [2] | |
Depth | 15.0 km |
Epicenter | 22°21′N96°14′E / 22.35°N 96.24°E |
Fault | Sagaing Fault |
Type | Strike-slip |
The 1946 Sagaing earthquakes (also known as the Wuntho earthquakes) struck central Burma at 15:17 local time on 12 September. [3] The first earthquake measured a magnitude of 7.3 Mw and was followed by a 7.7 Mw earthquake. Both events remain some of the largest in the country since the 1762 Arakan earthquake. [3] [4]
Both the mainshock and aftershock occurred along the Sagaing Fault; a continental transform fault boundary that links the Andaman Spreading Center to the south and the Main Himalayan Thrust to the north. [5] It defines the boundary between the Burma plate and Sunda plate. The Sagaing Fault is the most active geological structure in the country and poses significant risks to major cities such as Yangon, Mandalay, and Naypyidaw. Another major tectonic feature in Myanmar is the Sunda Megathrust that runs off the coast of Western Myanmar and the Kabaw Fault that traces the foothills of the Arakan Mountains and Indo-Burman Range.
The Mw 7.3 earthquake ruptured along the Sagaing Fault. It had a rupture length of approximately 80 kilometres (50 mi), and possibly as long as 155 kilometres (96 mi) along the Indaw segment. [6] A second shock of magnitude Mw 7.7 came three minutes later and ruptured south of the first event for a length of 185 kilometres (115 mi). [1] The latter earthquake ruptured along the Sagaing segment, through the villages of Tagaung and Thabeikkyin. [6]
From observing the historical records of earthquakes, the years 1906 and 1908 saw two major events in the northernmost end of the Sagaing Fault. [7] The 1906 Putao earthquake on August 31 had an estimated moment magnitude Mw of 7.0, and the 1908 earthquake measured Mw 7.5. [8] [9] Coulomb stress transfer to the south from the 1906 quake triggered rupture of the fault in the stressed area in 1908.
The 1908 earthquake resulted in the accumulation of stress towards the south, where the future 1931 Ms 7.7 earthquake would take place. Similarly, the 1946 earthquake rupture segments were directly south of the 1931 rupture. The first mainshock in the 1946 doublet sequence then triggered the second mainshock due to the sudden increase in stress levels on the fault. [7]
Ten years later, an Mw 7.1 earthquake near Mandalay killed at least 40 people. That earthquake broke a 60-kilometre (37 mi) segment south of the 1946 rupture. In 1991, a seismic gap between the two 1946 ruptures generated an Mw 7.0 earthquake, partially re-rupturing a 49-kilometre (30 mi) section of the 1946 ruptures. Another Mw 6.8 earthquake in 2012 partially ruptured the Sagaing segment. [6]
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.
At 23:28 local time on June 4, 2000, southern Sumatra, Indonesia was struck by an earthquake of moment magnitude 7.9 with a maximum Mercalli intensity of VI (Strong). The event occurred off the coast near Enggano Island. There were more than 100 fatalities and up to 2,585 injuries. Over 730 aftershocks shook the area afterwards, one just eleven minutes after the mainshock.
The 2000 New Ireland earthquakes occurred off the coast of New Ireland Province, Papua New Guinea on November 16 and 17.
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The Sagaing Fault is a major fault in Myanmar, a mainly continental right-lateral transform fault between the Indian Plate and Sunda Plate. It links the divergent boundary in the Andaman Sea with the zone of active continental collision along the Himalayan front. It passes through the populated cities of Mandalay, Yamethin, Pyinmana, the capital Naypyidaw, Toungoo and Pegu before dropping off into the Gulf of Martaban, running for a total length of over 1200 kilometers.
The 1943 Alahan Panjang earthquakes occurred on June 8 and June 9 UTC in Sumatra, then under Japanese occupation. This was an earthquake doublet.
The 2012 Shwebo earthquake occurred at 07:42 local time on 11 November in Myanmar. It had a magnitude of 6.8 on the moment magnitude scale and a maximum perceived intensity of VIII (Severe) on the Mercalli intensity scale. The epicenter was near the town of Male, 52 km NNE of the city of Shwebo, 64 km west of Mogok and 120 km north of Mandalay. Significant damage and possible casualties have been reported from near the epicenter, with up to 26 people dead and many more injured. Part of a bridge under construction fell into the Irrawaddy River near Shwebo and a gold mine collapsed at Sintku. An aftershock with a magnitude of 5.8 followed at 17:24 local time.
The 1930 Pyu earthquake occurred on December 4 at 01:21 local time. The epicenter was located north to Bago, Burma, then part of British India. The magnitude of the earthquake was estimated at Mw 7.3, or Ms 7.3.
The 1975 Bagan earthquake occurred on July 8 at 6:34 pm local time in Bagan, Myanmar. Many important stupas and temples were destroyed. The strongest intensity was felt in the towns of Nyaung-U, Pakokku, and Yesagyo, and in the Myaing townships on the confluence of the Ayeyawady River. Damage was also reported in Chauk and Natmauk townships. It had a magnitude of Mw 7.0.
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 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 1839 Ava earthquake, also known as the Amarapura earthquake or Inwa earthquake, was a disastrous seismic event that struck present-day central Myanmar on March 23. This earthquake with an estimated moment magnitude as high as 8.3, was one of the largest in the country, since 1762. It was assigned a maximum of XI (Extreme) on the Modified Mercalli intensity scale, and was felt in Rangoon and Bhamo. Damage was enormous in Ava, resulting in the death of hundreds.
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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, it killed 11 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.
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