On Sunday 18 September 2011, slightly after ten-past-six in the evening an earthquake with a magnitude of 6.9 on the Richter Scale occurred in the southern Himalayas, roughly 42 km to the northwest of Gangtok, the capital of the Indian province of Sikkim, at a depth of 19.7 km. This was large enough and shallow enough to cause widespread damage and casualties in several nations.
The epicenter of the quake was across the border in the Kanchenjunga Conservation Area in Nepal, an area of protected forests and mountains that continues east into Sikkim as the Kangchengdzonga National Park and northward into Tibet as the Qomolangma Biosphere Reserve. This makes the area where the quake occurred fairly sparsely populated, which will have kept the number of casualties down, but which also means that people who have been effected will be a long way from help. Several days after the quake reports of casualties are still coming in.
The Sikkim/Nepal border region is extremely mountainous with few roads and those roads that do exist have been widely damaged by landslides, hampering attempts to reach remote communities.
On the Indian side of the border 5000 troops have been deployed to Sikkin to assist the local authorities, and have set up emergency camps to house over 2000 people made homeless by the quake. At least 150 people have been admitted to hospital and 42 have been confirmed dead. A number of buildings are reported to have collapsed in Gangtok, the state capital, and rescuers are still sifting through the rubble, so the death toll may rise. There are a number of hydro-electric dams in Sikkim, but none of these appear to have been damaged. There are also reports of four deaths in west Bengal State and two in Bihar.
The remains of a Buddhist monastery in Gangtok.
In Nepal nine people were reported killed and over a hundred injured. Of these six of the fatalities and half the injuries were in the capital, Kathmandu, 272 km to the west of the epicenter. This was largely due to overcrowding and poor building standards in the city, which has grown rapidly in the last couple of decades as people have fled a bloody civil war which lasted from 1996 till 2006. A wall of the British Embassy is reported to have collapsed, killing three people.
Survivors surveying damage in Kathmandu.
In Tibet landslides closed a number of roads and seven people have been reportedly killed. The quake was also felt in Bhutan and Bangladesh, though there are no reports of any casualties in either country.
The Himalayas are highly prone to earthquakes as they are located on a convergent plate margin, where the Indian Plate is colliding with the Eurasian. Other convergent plate margins are associated with volcanic activity, for example in the Andes where the Pacific Plate is being subuducted beneath the South American, but since both India and Eurasia are continental land masses this cannot occur so they have been forced upwards creating the Himalayan Mountains and the Tibetan Plateau.
This has lead to many devastating earthquakes in the region.
In 2005 an earthquake in Kashmir killed between 75 000 and 80 000 people (possibly more) in Pakistan, India and Afghanistan. The capital of Pakistan-administered Kashmir, Muzzaffarabad and the neighboring city of Bagh were partially destroyed and much of the infrastructure in the region collapsed. This was followed by a major international aid effort, which was marred by allegations of corruption in the Pakistani military.
Rescuers sifting through the remains of Balakot, near the Khyber Pass in Pakistan.
In 1991 over 2000 people were killed by a quake in Uttarkhashi, in the Indian state of Uttarakhand, to the northwest of Nepal.
In 1950 an earthquake on the Assam/Tibbet border killed over 1500 people.
In 1934 an earthquake in Nepal killed over 8500 people and destroyed over 80 000 buildings.
In 1897 an earthquake in Assam killed over 1500 people in India, Bhutan and Burma, and damaged buildings as far away as Delhi.
GeoHazards International, a US based non-profit organization which seeks to lessen the impact of earthquakes and other geological hazards through forward planning, has identified Kathmandu as the worlds most at-risk city for potential earthquake damage. The city lies in an area where major earthquakes happen on average once every 75 years, and where there has not been a quake for 77 years, making one overdue. On top of this the city has expanded rapidly in recent years, it now houses over 2 million people, but with few concessions to the potential threat of earthquakes. Building standards tend to be poor, with almost no earthquake-proofed buildings, and the city can only be reached by three roads and an airport.
Overcrowded Kathmandu is thought to be extremely vulnerable to earthquakes.
See also Earthquake in Mojen, northern Iran, Magnitude 5.1 Earthquake in Western Tibet/Xizang and Earthquakes on Sciency Thoughts YouTube.