The 1995 Menglian earthquake or Myanmar–China earthquake occurred on 12 July at 05:46 local time in the Myanmar–China border region. The earthquake had an

epicenter 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. Determination The primary purpose of a ...

on the

Myanmar Myanmar, officially the Republic of the Union of Myanmar; and also referred to as Burma (the official English name until 1989), is a country in northwest Southeast Asia. It is the largest country by area in Mainland Southeast Asia and has ...

side of the border, located in the mountainous region of

Shan State Shan State (, ; , ) is a administrative divisions of Myanmar, state of Myanmar. Shan State borders China (Yunnan) to the north, Laos (Louang Namtha Province, Louang Namtha and Bokeo Provinces) to the east, and Thailand (Chiang Rai Province, Chia ...

. It registered 7.3 on the Chinese

surface-wave magnitude The surface wave magnitude (M_s) scale is one of the magnitude scales used in seismology to describe the size of an earthquake. It is based on measurements of Rayleigh surface waves that travel along the uppermost layers of the Earth. This mag ...

scale () and 6.8 on the

moment magnitude scale The moment magnitude scale (MMS; denoted explicitly with or Mwg, and generally implied with use of a single M for magnitude) is a measure of an earthquake's magnitude ("size" or strength) based on its seismic moment. was defined in a 1979 paper ...

(). 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 Chiang Mai, sometimes written as Chiengmai or Chiangmai, is the largest city in northern Thailand, the capital of Chiang Mai province and the List of municipalities in Thailand#Largest cities by urban population, second largest city in Thailan ...

and

Chiang Rai Chiang Rai (, ; , ) is the northernmost major city in Thailand, with a population of about 200,000 people. It is located in Mueang Chiang Rai District, Chiang Rai Province. Chiang Rai was established as a capital city in the reign of King Ma ...

Thailand Thailand, officially the Kingdom of Thailand and historically known as Siam (the official name until 1939), is a country in Southeast Asia on the Mainland Southeast Asia, Indochinese Peninsula. With a population of almost 66 million, it spa ...

. 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.

Tectonic setting

The Shan Plateau which encompass Yunnan and Shan State is crisscrossed by strike-slip structures to accommodate crustal rotation of the Sunda Block and deformation as a result of the India-Asia collision where the

Indian plate The Indian plate (or India plate) is or was a minor tectonic plate straddling the equator in the Eastern Hemisphere. Originally a part of the ancient continent of Gondwana, the Indian plate broke away from the other fragments of Gondwana an ...

is underthrusted beneath the Eurasian plate. The Shan Plateau formed by uplift along the Shan Scarp Fault Zone, an inactive

shear zone In geology, a shear zone is a thin zone within the Earth's crust or upper mantle that has been strongly deformed, due to the walls of rock on either side of the zone slipping past each other. In the upper crust, where rock is brittle, the shear ...

and reverse or

thrust fault A thrust fault is a break in the Earth's crust, across which older rocks are pushed above younger rocks. Thrust geometry and nomenclature Reverse faults A thrust fault is a type of reverse fault that has a dip of 45 degrees or less. I ...

along its western base. Located east of the Shan Scarp Fault is the active

Sagaing Fault 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 t ...

, a dextral

transform fault A transform fault or transform boundary, is a fault (geology), fault along a plate boundary where the motion (physics), motion is predominantly Horizontal plane, horizontal. It ends abruptly where it connects to another plate boundary, either an ...

that separates the Burma plate from the

Sunda plate The Sunda plate is a minor tectonic plate straddling the equator in the Eastern Hemisphere on which the majority of Southeast Asia is located. The Sunda plate was formerly considered a part of the Eurasian plate, but the GPS measurements hav ...

. At the northern boundary of the Shan Plateau lies the Red River Fault, an active 1,000 km-long dextral fault. Bookshelf-style faulting as a result of shear deformation between the Red River and Sagaing faults have resulted in predominantly right-lateral strike-slip faulting within the Shan Plateau.

Earthquake

The earthquake occurred as a result of dextral strike-slip faulting at a shallow depth in the Shan Plateau. It ruptured a previously unmapped northwest–southeast striking strike-slip structure not far from the faults involved in the

1988 Lancang–Gengma earthquakes On 6 November 1988, two earthquakes struck Lancang Lahu Autonomous County, Lancang and Gengma Dai and Va Autonomous County, Gengma counties, Yunnan, near the China–Myanmar border. These earthquakes measured moment magnitude () 7.0 and 6.9, resp ...

. Strike-slip faulting within the Shan Plateau are the result of "bookshelf-style" faulting, caused by crustal deformation as it is situated between the

and Red River Fault. The 1995 earthquake may have been triggered by increased

coulomb stress transfer Coulomb stress transfer is a Seismology, seismic-related geology, geological process of Stress (mechanics), stress changes to surrounding material caused by local discrete deformation events. Using mapped displacements of the Earth's surface during ...

from the 1988 earthquake. Modelling of the earthquake suggest most of the displacements in the southeastern rupture zone occurred at depths of . The greatest slip was detected at beneath the surface, having moved by . In the northwestern rupture, the fault had a maximum slip of detected at depth. Rupture was also detected on the surface. The total length of the northwestern and southeastern rupture is approximately .

Foreshocks and aftershocks

In the days leading up to the

mainshock In seismology, the mainshock is the largest earthquake in a sequence, sometimes preceded by one or more foreshocks, and almost always followed by many aftershocks. Foreshock A foreshock is an earthquake that occurs before a larger seismic ev ...

in this earthquake sequence, there was a series of

foreshock A foreshock is an earthquake that occurs before a larger seismic eventthe mainshockand is related to it in both time and space. The designation of an earthquake as ''foreshock'', ''mainshock'' or aftershock is only possible after the full sequenc ...

s. The largest of which measured 5.5 and 6.2 on the

Richter scale The Richter scale (), also called the Richter magnitude scale, Richter's magnitude scale, and the Gutenberg–Richter scale, is a measure of the strength of earthquakes, developed by Charles Richter in collaboration with Beno Gutenberg, and pr ...

(). According to the Yunnan Seismic Network Center, in the 100 days after the 7.3 mainshock, some 872

aftershocks In seismology, an aftershock is a smaller earthquake that follows a larger earthquake, in the same area of the main shock, caused as the displaced crust adjusts to the effects of the main shock. Large earthquakes can have hundreds to thousands ...

were recorded with a magnitude greater than 2.0 . Most of the aftershocks were recorded within the first 100 days after the earthquake. The aftershocks only released 4% of the total energy released during the mainshock. The

United States Geological Survey The United States Geological Survey (USGS), founded as the Geological Survey, is an agency of the U.S. Department of the Interior whose work spans the disciplines of biology, geography, geology, and hydrology. The agency was founded on Mar ...

recorded the largest foreshocks at 5.9 and 5.0 . Three additional foreshocks had magnitudes of 4.9 or 4.7. The 5.9 foreshock caused some damage in Menglian County and was felt in Thailand.

Prediction

Between 19 September 1994 and 12 May 1995, a cluster of earthquakes measuring 4.7 or greater was detected on the Myanmar-China border region. Seismologists also detected strange anomalies in the seismological parameters in that region. Changes to water levels in

Shidian County Shidian County () is under the administration of the prefecture-level city of Baoshan, in the west of Yunnan Yunnan; is an inland Provinces of China, province in Southwestern China. The province spans approximately and has a population o ...

were also interpreted as signs of a large earthquake. After the 6.2 foreshock on July 10, the Yunnan Seismological Bureau dispatched a team to the region closest to the epicenter. A meeting was also conducted and seismologists concluded that a mainshock of magnitude of ~7.0 should strike. An evacuation order was recommended by scientists from the Yunnan Provincial Earthquake Administration after the forecast. Less than 30 hours after that forecast, the mainshock struck.

Intensity

The area with the greatest shaking intensity was in Myanmar. In Yunnan Province, the earthquake was strongly felt over an area . The districts and prefectures in Yunnan that were affected included the Simao District,

Linxiang District Linxiang District () is a district of the city of Lincang, Yunnan province, China. It borders Jingdong County Jingdong Yi Autonomous County (; ) is an autonomous county in southern Yunnan Province, China. It is the northernmost county-level di ...

and

Xishuangbanna Dai Autonomous Prefecture Xishuangbanna, sometimes shortened to Banna, is one of the eight autonomous prefectures of Yunnan Province. The autonomous prefecture for Dai people is in the extreme south of Yunnan province, China, bordering both Myanmar and Laos. Xishuangbanna ...

. Thirty-nine townships and 2,242 villages across five counties; Menglian, Ximeng, Lancang, Cangyuan and Menghai were located within the earthquake zone, impacting an estimated 127,420 households housing 577,188 people. Intensity VIII on the China seismic intensity scale covered an area of 110 km² in Yunnan. Many brick and wood constructed walls of residential buildings suffered large cracks. Structural deformation to roof trusses and some building collapses occurred within this intensity zone. North-east and northwest-trending

fissure A fissure is a long, narrow crack opening along the surface of Earth. The term is derived from the Latin word , which means 'cleft' or 'crack'. Fissures emerge in Earth's crust, on ice sheets and glaciers, and on volcanoes. Ground fissure A ...

s up to wide were reported. These fissures ran for approximately 2 km. Some minor landslides were also observed. The zone of intensity VII extended north at Wenggake of Ximeng County,

Menglian County Menglian Dai, Lahu and Va Autonomous County (; Awa: ) is an autonomous county in the southwest of Yunnan Province, China, bordering Ximeng County to the north, Lancang County to the north, northeast, and east, and Burma's Shan State Shan ...

in the east and Lalei in the south for an area of . Many brick and wood constructed homes in this zone were severely cracked. Many walls were either badly damaged or had totally collapsed. Some roof shingles on homes also suffered major damage during the tremor. Intensity VI zone covered a area, from extends to Nuoliang in Cangyuan County in the north, Fubang in Lancang County in the east, and Daluo in Menghai County in the south. Most masonry and wooden buildings had minor damage such as small cracks in the walls. Minimal damage on roof shingles on most structures in the zone. Overall, most structures had limited damage because they were well retrofitted and constructed with seismic codes in place after the 1988 earthquakes.

Aftermath

A preliminary report by the UN Department of Humanitarian Affairs on July 12 said two women died of heart attacks while 36 individuals were injured, two of them seriously. Nineteen buildings were destroyed while many schools, factories and public infrastructures were damaged. A team of scientists were assigned to survey the area but could not reach the affected area due to road damage. In Chiang Rai, Thailand, the earthquake damaged a major electrical generator, cutting power. The Government of Thailand also ordered that dams reserviors and bridges be inspected for damage. According to an estimate by

Xinhua news agency Xinhua News Agency (English pronunciation: ),J. C. Wells: Longman Pronunciation Dictionary, 3rd ed., for both British and American English or New China News Agency, is the official state news agency of the People's Republic of China. It is a ...

on July 19, the total damage caused by earthquake was US$36 million. At least 329 schools, 143 hospitals, 200,000 homes, 165 government offices and more than 500 factories and military bases in Menglian, Ximeng, Lancang and Cangyuan counties were significantly damaged by the quake. The death toll was also revised to 11 while the number of injured rose to 136. A further 600,000 people were impacted by the quake as well. After the mainshock struck, the Yunnan Seismological Bureau immediately entered a state of emergency, establishing headquarters and sending more scientists to Menglian to plan disaster assessments, inspections, surveillance, and send reports. The National Earthquake Administration and the People's Government of Yunnan Province formally praised the Yunnan Seismological Bureau for the prediction of the earthquake, resulting in a minimal loss of life.

References

External links

* {{DEFAULTSORT:1995 Myanmar-China earthquake 1995 earthquakes Earthquakes in Myanmar Earthquakes in Yunnan 1995 in China 1995 in Myanmar July 1995 in Asia 1995 in science 1995 disasters in China 1995 disasters in Myanmar July 1995 in China