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A strong
earthquake (M6.0-6.9 termed as "strong") occurred
in eastern Nepal near the Nepal-Sikkim border on 18 September 2011
at 18:10 IST. This earthquake has caused significant fatalities, widespread damage and
landslides in many parts of eastern Nepal, Sikkim and north
Bengal. It had a magnitude of Mw=6.9 and is the largest
instrumented earthquake in this region. It is also possibly the
largest earthquake to originate in this immediate region in
historical record.
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Aftershock advisory:
Given the magnitude of this earthquake it would be reasonable
to expect aftershocks in the M5.0-5.7 range. Aftershocks decay
in magnitude and frequency with respect to the time elapsed since the mainshock. Thus
the probability of these occurring reduces with time. That
said, please bear in mind, large aftershocks can occur
several weeks or months following the mainshock. |
This earthquake was centred
11.5 kms NW of Kanchenjunga (Sikkim), India,
13 kms NE of Khunsa (Mechi), Nepal,
29 kms NNW of Dzongri (Sikkim), India,
40 kms WSW of Jathang (Sikkim), India,
52 kms NW of Mangan (Sikkim), India,
70 kms NW of Gangtok (Sikkim), India,
83 kms NNW of Kalimpong (West Bengal), India,
91.8 kms NNE of Ilam (Mechi), Nepal,
117 kms NNW of Shiliguri (West Bengal), India,
161 kms NNE of Biratnagar (Kosi), Nepal.
If you felt this earthquake (especially
in western and southern West Bengal) please click
here to view a felt map and to fill out a report.
At least 90 people
were killed in this earthquake (10 AM IST, 28 September
2011). The largest number of fatalities occurred in India and
amongst these the largest loss of life was in the state of Sikkim.
Elsewhere in India, fatalities were reported in Bihar, Jharkhand
and West Bengal. One fatality has also been blamed on this
earthquake in Haryana. Deaths also occurred in eastern Nepal in
the Kosi, Mechi and Sagarmatha divisions. Three fatalities also
occurred in the Kathmandu valley. One person was also killed in
Bhutan and seven in southern Tibet.
In Sikkim, major
damage occurred in the district of North Sikkim including in
the Mangan-Chumthang area along with several significant landsides
and rock falls. Modern buildings were heavily damaged at Chumthang
and Jorthang. Media reports claimed a number of villages north of
Mangan such as Sakyong have been entirely destroyed but this has
not been verified. In the state capital Gangtok, the earthquake
caused widespread panic with many running outdoors. A number of
structures in the city were badly damaged and some precariously
perched buildings completely collapsed down hillsides. Highways
and other roads were blocked by landslides and rock falls. A
number of deaths have taken place as a result of these throughout
the state. This is possibly the most damaging earthquake in Sikkim
since 1800.
In eastern Nepal,
significant damage occurred in the divisions of Kosi, Mechi and
Sagarmatha. The worst affected are the districts of Panchthar,
Taplejung and Terathum where a number of public and private
buildings have either sustained heavy damage or have been completely
destroyed. Significant damage also extended into other districts
such as Sankhusabha and Solukhumbu. Damage and fatalities also
occurred parts of Dharan, Dhankuta and Ilam. The earthquake caused
widespread panic across extensive parts of the east of the country
resulting in very many injuries as people rushed out into the open.
In the Kathmandu Valley, tremors frightened people outdoors and
loose objects were knocked over. Isolated damage occurred at
Bhaktapur, Lainchaur, Sankhu, Sundhara and Syachater. In Bhaktapur,
the facades of a few buildings completely collapsed while at
Lainchaur in the Kathmandu area, the perimeter wall of the British
Embassy collapsed fatally. Damage was also reported from as far as
Nuwakot and Sindhupalchowk districts. This is the most damaging
earthquake in Nepal since the 1988 Udaypur Gahri earthquake.
Damage and fatalities
also occurred in the Chumbi Valley in southern Tibet as well as in
western Bhutan. In Tibet, as many as seven people were killed and
over 200 hurt in the Galingang-Yadong area with damage extending
into the adjoining districts of Dinggye and Gamba. In Bhutan, damage
was significant in the Haa dzong, most notably in the Bji and Katsho
gewogs where buildings including chortens and dzongs were either
heavily damaged or partially collapsed. Damage also occurred in
Chhuka, Dagana, Gasa, Paro, Thimphu and Samtse dzongs. Damage was
also reported from central and eastern dzongs such as Samdrup
Jongkar, Trashigang and Trongsa. In the capital Thimphu many people
ran outdoors when the earthquake struck and a few buildings
sustained minor cracks or lost pieces of plaster. Landslides and
rock falls blocked many highways and mountain roads in the west of
the country.
In north Bengal, the earthquake caused some damage, a few fatalities
and many injuries in the Darjeeling, Jalpaiguri, Kalimpong and
Siliguri areas. Many people ran outdoors and a number were struck by
falling masonry. Damage also occurred in a number of tea estates in
the region with at least one fatality was attributed to the
complete collapse of a building in the Nideen Tea Estate. A levee
was also damaged near Jalpaiguri. Severe tremors were felt in most
parts of the region including at Alipurduars, Dim Dam, Mal Bazaar,
Matabhanga and other places. This is the most damaging earthquake to
have affected north Bengal since the 1930 Dhubri earthquake.
Southward, damage was reported in West Bengal from Maldah,
Murshidabad and Uttar Dinajpur. As far south as Kolkata, a few
buildings developed cracks and people ran out of high-rise
buildings.
Shaking from this
earthquake has been felt over a large part of the Subcontinent
including as far west as Ahmedabad, Ajmer, Jaipur and Indore in western India and as far
south as Nagpur in central India. In lower Assam, the shock was
severely felt with damage reported at Dhubri. Many modern
apartment buildings were damaged in the city of Guwahati. Seismic
seiches were observed in the Bramhaputra River in central Assam
during the earthquake. In north-eastern India, the earthquake was
felt at Itanagar in Arunachal Pradesh, at Dimapur, Mokokchung and
Kohima in Nagaland, at Imphal in Manipur and at Jowai, Shillong
and Tura in Meghalaya. Buildings developed cracks or isolated wall
collapses occurred in the districts of north Bihar such as Araria,
Madhubani, Katihar, Samastipur, Sitamarhi and Purnea. Damage and
widespread panic also occurred in the districts of Bhagalpur,
Munger and Patna. Similarly in Jharkhand, damage was reported from
Dhanbad, Godda, Hazaribagh, Ranchi and north-eastern parts of the
state. Shaking was relatively strong in many parts of eastern
Uttar Pradesh including at Deoria, Ghazipur, Gorakhpur,
Siddharthnagar and Varanasi. Westward it was felt lightly or by
people in tall buildings in places such as Agra, Aligarh, Amethi,
Farukhabad, Lucknow, Kanpur and Rai Bareili. In Madhya Pradesh, it
was felt in districts adjoining Uttar Pradesh such as Bhind, Datia
and Gwalior as well as in tall buildings in Bhopal, Jabalpur,
Hoshangabad and Indore. In Chhattisgarh, the earthquake was
strongly felt in the northern part of the state and caused minor
damage in the Bilaspur area. In other parts of India, the
earthquake was felt in tall buildings in the Bhubaneswar-Cuttack
area in Orissa and in Delhi, Ghaziabad, Faridabad and Gurgaon in
the NCR.
In Bangladesh, the
earthquake caused panic in the northern districts in Rajshahi
division. Many people were hurt in stampedes at places such as
Gaibandha and Rangpur. Elsewhere, buildings sustained minor damage
and isolated wall collapses were reported from Brahmanbaria, Bogra,
Lalmonirhat, Natore, Nilphamari, Kishorganj and Panchagarh. In the
capital Dhaka, people in tall buildings ran outdoors in panic.
Minor damage is believed to have been sustained by a few high-rise
buildings in the city. Southward, the shock was perceptible at
places such as Barguna and Chittagong. Seismic seiches were
observed in rivers in the Sunderbans.
If you felt this earthquake (especially
in western and southern West Bengal) please click
here to view a felt map and to fill out a report.
The USGS and GFZ
mechanisms for this earthquake indicate strike-slip faulting. This
is the strongest earthquake to have occurred locally in this
region in the known historical record. The last Mw>6.0 earthquake in this region
occurred on 19 November 1980 and had a magnitude of Mw 6.3. The 1934
Mw 8.1 Nepal-Bihar and the 1988 Mw 6.8 Udaypur
Gahri earthquakes also caused
significant damage in this region. Recently on
14 February 2006, a moderate M5.3 earthquake
caused some damage and two fatalities in north-central Sikkim.
GFZ MOMENT TENSOR SOLUTION
Depth 30 No. of sta: 71
Moment Tensor; Scale 10**19 Nm
Mrr=-0.38 Mtt=-1.70
Mpp= 2.09 Mrt= 1.23
Mrp=-0.44 Mtp=-1.70
Principal axes:
T Val= 2.34 Plg=15 Azm= 77
N 0.12 56 324
P -2.46 30 176
Best Double Couple:Mo=2.4*10**19
NP1:Strike=309 Dip=80 Slip=-146
NP2: 213 58 -11
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