The April 2015 Nepal earthquake (also known as the Gorkha earthquake) killed nearly 9,000 people and injured nearly 22,000. It occurred at 11:56 Nepal Standard Time on 25 April, with a magnitude of 7.8Mw or 8.1Ms and a maximum Mercalli Intensity of IX (Violent). Its epicenter was east of Gorkha District at Barpak, Gorkha, and its hypocenter was at a depth of approximately 8.2 km (5.1 mi). It was the worst natural disaster to strike Nepal since the 1934 Nepal–Bihar earthquake. The ground motion recorded in Kathmandu valley was of low frequency which, along with its occurrence at an hour where many people in rural areas were working outdoors, decreased the loss of property and human life.
The earthquake triggered an avalanche on Mount Everest, killing 21, making April 25, 2015 the deadliest day on the mountain in history. The earthquake triggered another huge avalanche in the Langtang valley, where 250 people were reported missing.
Hundreds of thousands of people were made homeless with entire villages flattened, across many districts of the country. Centuries-old buildings were destroyed at UNESCO World Heritage sites in the Kathmandu Valley, including some at the Kathmandu Durbar Square, the Patan Durbar Square, the Bhaktapur Durbar Square, the Changu Narayan Temple, the Boudhanath stupa and the Swayambhunath Stupa. Geophysicists and other experts had warned for decades that Nepal was vulnerable to a deadly earthquake, particularly because of its geology, urbanization, and architecture.
Continued aftershocks occurred throughout Nepal at the intervals of 15–20 minutes, with one shock reaching a magnitude of 6.7 on 26 April at 12:54:08 NST. The country also had a continued risk of landslides.
A major aftershock occurred on 12 May 2015 at 12:50 NST with a moment magnitude (Mw) of 7.3. The epicenter was near the Chinese border between the capital of Kathmandu and Mt. Everest. More than 200 people were killed and more than 2,500 were injured by this aftershock.
Aftershocks at 12 May
The earthquake occurred on 25 April 2015 at 11:56 a.m. NST (06:11:26 UTC) at a depth of approximately 15 km (9.3 mi) (which is considered shallow and therefore more damaging than quakes that originate deeper in the ground), with its epicentre approximately 34 km (21 mi) east-southeast of Lamjung, Nepal, lasting approximately fifty seconds. The earthquake was initially reported as 7.5 Mw by the United States Geological Survey (USGS) before it was quickly upgraded to 7.8 Mw. The China Earthquake Networks Center (CENC) reported the earthquake's magnitude to be 8.1 Ms. The India Meteorological Department (IMD) said two powerful quakes were registered in Nepal at 06:11 UTC and 06:45 UTC. The first quake measured 7.8 Mw and its epicenter was identified at a distance of 80 km to the northwest of Kathmandu, the capital of Nepal. Bharatpur was the nearest major city to the main earthquake, 53 km (33 mi) from the epicenter. The second earthquake was somewhat less powerful at 6.6 Mw. It occurred 65 km (40 mi) east of Kathmandu and its seismic focus lay at a depth of 10 km (6.2 mi) below the earth's surface. Over thirty-eight aftershocks of magnitude 4.5 Mw or greater occurred in the day following the initial earthquake, including the one of magnitude 6.8 Mw.
According to the USGS, the earthquake was caused by a sudden thrust, or release of built-up stress, along the major fault line where the Indian Plate, carrying India, is slowly diving underneath the Eurasian Plate, carrying much of Europe and Asia. Kathmandu, situated on a block of crust approximately 120 km (74 miles) wide and 60 km (37 miles) long, reportedly shifted 3 m (10 ft) to the south in a matter of just 30 seconds.
The risk of a large earthquake was well known beforehand. In 2013, in an interview with seismologist Vinod Kumar Gaur, The Hindu quoted him as saying, "Calculations show that there is sufficient accumulated energy [in the Main Frontal Thrust], now to produce an 8 magnitude earthquake. I cannot say when. It may not happen tomorrow, but it could possibly happen sometime this century, or wait longer to produce a much larger one. "According to Brian Tucker, founder of a nonprofit organization devoted to reducing casualties from natural disasters, some government officials had expressed confidence that such an earthquake would not occur again. Tucker recounted a conversation he had had with a government official in the 1990s who said, "We don't have to worry about earthquakes anymore, because we already had an earthquake"; the previous earthquake to which he referred occurred in 1934.
Source : wikipedia.org
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