- More than 4,300
people die after amagnitude-7.8 earthquake strikes Nepal.
- Nepal's Prime
Minister, Sushil Koirala, has said that the number could reach 10,000
The 2015 Nepal
earthquake (the Himalayan earthquake) which is believed to have killed more
than 6,100 people as of 29 April 2015, occurred at 11:56 NST on 25 April with a
moment magnitude (Mw) of 7.8 or 8.1Ms and a maximum Mercalli Intensity of IX
(Violent). Its epicenter was approximately 34 km (21 mi) east-southeast of
Lamjung, Nepal, and its hypocenter was at a depth of approximately 15 km (9.3
mi).
It was the most
powerful disaster to strike Nepal since the 1934 Nepal–Bihar earthquake. Some
casualties have also been reported in the adjoining areas of India, China, and
Bangladesh. India responded with Operation Maitri for rescue and relief in
Nepal by its armed forces and also evacuated Indian and foreign citizens from
Nepal.
The earthquake
triggered an avalanche on Mount Everest, killing at least 19,making it the
deadliest day on the mountain in history. It triggered another huge avalanche
in Langtang valley, where 250 are now missing.Centuries-old buildings were
destroyed at UNESCO World Heritage sites in the Kathmandu Valley, including
some at the Kathmandu Durbar Square, the PatanDurbar Square and the Bhaktapur
Durbar Square. Nepal's government has declared three days of mourning after the
quake.
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, with one shock reaching a magnitude of
6.7 on 26 April at 12:54:08 NST. The country is at continued risk of landslides
as well.
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
epicenterapproximately 34 km (21 mi) east-southeast of Lamjung, Nepal, lasting
approximately twenty seconds. The earthquake was initially reported as 7.5 Mw
by the United States Geological Survey (USGS) before it was quickly upgraded to
7.9 Mw and finally downgraded to 7.8 Mw. The China Earthquake Networks Center
(CENC) reported the earthquake's magnitude to be 8.1 Ms. India Meteorological
Department (IMD) said two powerful quakes were registered in Nepal at 06:11 UTC
and 06:45 UTC. The w and its epicenter was identified at a distance of 80 km to
the northwest of the capital Kathmandu. The second earthquake was somewhat less
powerful at 6.6 Mw. The seismic focus lay at a depth of 10 km (6.2 mi) below
the earth's surface. Bharatpur was the nearest major city to the main
earthquake, 53 km (33 mi) from the epicenter. The second earthquake occurred 81
km (50 mi) northwest of Kathmandu, the capital of Nepal. Over thirty-five
aftershocks of magnitude 4.5 Mw or greater occurred in the day following the
initial earthquake, including the one of magnitude 6.6 Mw.
Nepal lies towards the southern limit of the
diffuse collisional boundary where the Indian Plate underthrusts the Eurasian
Plate,occupying the central sector of the Himalayan arc, nearly one-third of
the 2,400 km (1,500 mi) long Himalayas. Geologically, the Nepal Himalayas are
sub-divided into five tectonic zones from north to south, east to west and
almost parallel to sub-parallel. These five distinct morpho-geotectonic zones
are: (1) Terai Plain, (2) Sub Himalaya (Sivalik Range), (3) Lesser Himalaya
(Mahabharat Range and mid valleys), (4) Higher Himalaya, and (5) Inner Himalaya
(Tibetan Tethys). Each of these zones is clearly identified by their
morphological, geological, and tectonic features.
The convergence
rate between the plates in central Nepal is about 45 mm (1.8 in) per year. The
location, magnitude, and focal mechanism of the earthquake suggest that it was
caused by a slip along the Main Frontal Thrust.
The earthquake's
effects were amplified in Kathmandu as it sits on the Kathmandu Basin, which
contains up to 600 m (2,000 ft) ofsedimentary rocks, representing the infilling
of a lake.
Based on a study
published in 2014, of the Main Frontal Thrust, on average a great earthquake
occurs every 750 ± 140 and 870 ± 350 years in the east Nepal region. A study
from 2015 found a 700-year delay between earthquakes in the region. The study
also suggests that because of tectonic stress buildup, the earthquake from 1934
in Nepal and the 2015 quake are connected, following a historic earthquake
pattern.
According to
"Did You Feel It?" (DYFI?) responses on the USGS website, the
intensity in Kathmandu was IX (Violent). Tremors were felt in the neighboring
Indian states of Bihar, Uttar Pradesh, Assam, West Bengal, Sikkim, Uttarakhand,
Odisha, Andhra Pradesh,Gujarat, in the Indian capital region around New
Delhi[35] and as far south as Karnataka. Many buildings were brought down in
Bihar. Minor cracks in the walls of houses were reported in Odisha. Minor
quakes were registered as far as Kochi in the southern state of Kerala. The
intensity in Patna was V (Moderate).The intensity was IV (Light) in Dhaka,
Bangladesh. The earthquake was also experienced across southwestern China,
ranging from the Tibet Autonomous Region to Chengdu, which is 1,900 km (1,200
mi) away from the epicenter. Tremors were felt in Pakistan and Bhutan
A major aftershock of magnitude 6.7 Mw
occurred on 26 April 2015 in the same region at 12:55 NST (07:09 UTC), with an
epicenter located about 17 km (11 mi) south of Kodari, Nepal. The aftershock
caused fresh avalanches on Mount Everest and was felt in many places in
northern India including Kolkata, Siliguri, Jalpaiguri and Assam. The
aftershock caused a landslide on the Koshi Highway which blocked the section of
the road between Bhedetar and Mulghat.
A model of
GeoGateway, based on a United States Geological Survey mechanism of a
near-horizontal fault as well as location of aftershocks showed that the fault
was an 11° dip striking at 295°, 50 km (31 mi) wide, 150 km (93 mi) long, and
had a dip slip of 3 m (9.8 ft). The USGS says the aftershock on Sunday registered
at a shallow depth of 10 km (6.2 mi).
Nepal's Prime Minister, Sushil Koirala, has
said that the number could reach 10,000.
On 27 April, The
Himalayan Times reported that as many as 20,000 foreign nationals may have been
visiting Nepal at the time of the earthquake. As reports come in from isolated
villages, it is possible that total deaths may reach or exceed the more than
10,000 killed in the 1934 earthquake.Hundreds of people are still considered
missing and more than 450,000 are displaced.
As of 4:14 p.m. 27
April in India, Home Minister Rajnath Singh, confirmed that 56 people died in
the state of Bihar, 12 in Uttar Pradesh, 3 in West Bengal and 1 in Rajasthan.
first quake
measured 7.9 M
According to the
USGS, the temblor 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 (75 miles)
wide and 60 km (37 miles) long, reportedly shifted 3 m (10 ft) to the south in
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 MFT], 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
organisation 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.
